The Botanic Garden
by
Erasmus Darwin
Part 5 out of 7
land; any one may distinguish a snow-flood from a rain-flood by the
transparency of the water. Hence hills or fields with considerable
inclination of surface should be ploughed horizontally that the furrows
may stay the water from showers till it deposits its mud. 2. Snow
protects vegetables from the severity of the frost, since it is always
in a state of thaw where it is in contact with the earth; as the earth's
heat is about 48° and the heat of thawing snow is 32° the vegetables
between them are kept in a degree of heat about 40, by which many of
them are preserved. See note on Muschus, Vol. II. of this work.
NOTE XIII.--ELECTRICITY
_Cold from each point cerulean lustres gleam._
CANTO I. l. 339.
ELECTRIC POINTS.
There was an idle dispute whether knobs or points were preferable on the
top of conductors for the defence of houses. The design of these
conductors is to permit the electric matter accumulated in the clouds to
pass through them into the earth in a smaller continued stream as the
cloud approaches, before it comes to what is termed striking distance;
now as it is well known that accumulated electricity will pass to points
at a much greater distance than it will to knobs there can be no doubt
of their preference; and it would seem that the finer the point and the
less liable to become rusty the better, as it would take off the
lightening while it was still at a greater distance, and by that means
preserve a greater extent of building; the very extremity of the point
should be of pure silver or gold, and might be branched into a kind of
brush, since one small point can not be supposed to receive so great a
quantity as a thicker bar might conduct into the earth.
If an insulated metallic ball is armed with a point, like a needle,
projecting from one part of it, the electric fluid will be seen in the
dark to pass off from this point, so long as the ball is kept supplied
with electricity. The reason of this is not difficult to comprehend,
every part of the electric atmosphere which surrounds the insulated ball
is attracted to that ball by a large surface of it, whereas the electric
atmosphere which is near the extremity of the needle is attracted to it
by only a single point, in consequence the particles of electric matter
near the surface of the ball approach towards it and push off by their
greater gravitation the particles of electric matter over the point of
the needle in a continued stream.
Something like this happens in respect to the diffusion of oil on water
from a pointed cork, an experiment which was many years ago shewn me by
Dr. Franklin; he cut a piece of cork about the size of a letter-wafer
and left on one edge of it a point about a sixth of an inch in length
projecting as a tangent to the circumference. This was dipped in oil and
thrown on a pond of water and continued to revolve as the oil left the
point for a great many minutes. The oil descends from the floating cork
upon the water being diffused upon it without friction and perhaps
without contact; but its going off at the point so forcibly as to make
the cork revolve in a contrary direction seems analogous to the
departure of the electric fluid from points.
Can any thing similar to either of these happen in respect to the
earth's atmosphere and give occasion to the breezes on the tops of
mountains, which may be considered as points on the earths
circumference?
FAIRY-RINGS.
There is a phenomenon supposed to be electric which is yet unaccounted
for, I mean the Fairy-rings, as they are called, so often seen on the
grass. The numerous flashes of lightning which occur every summer are, I
believe, generally discharged on the earth, and but seldom (if ever)
from one cloud to another. Moist trees are the most frequent conductors
of these flashes of lightning, and I am informed by purchasers of wood
that innumerable trees are thus cracked and injured. At other times
larger parts or prominences of clouds gradually sinking as they move
along, are discharged on the moisture parts of grassy plains. Now this
knob or corner of a cloud in being attracted by the earth will become
nearly cylindrical, as loose wool would do when drawn out into a thread,
and will strike the earth with a stream of electricity perhaps two or
ten yards in diameter. Now as a stream of electricity displaces the air
it passes through, it is plain no part of the grass can be burnt by it,
but just the external ring of this cylinder where the grass can have
access to the air, since without air nothing can be calcined. This earth
after having been so calcined becomes a richer soil, and either funguses
or a bluer grass for many years mark the place. That lightning displaces
the air in its passage is evinced by the loud crack that succeeds it,
which is owing to the sides of the aerial vacuum clapping together when
the lightning is withdrawn. That nothing will calcine without air is now
well understood from the acids produced in the burning of phlogistic
substances, and may be agreeably seen by suspending a paper on an iron
prong and putting it into the centre of the blaze of an iron-furnace; it
may be held there some seconds and may be again withdrawn without its
being burnt, if it be passed quickly into the flame and out again
through the external part of it which is in contact with the air. I know
some circles of many yards diameter of this kind near Foremark in
Derbyshire which annually produce large white funguses and stronger
grass, and have done so, I am informed, above thirty years. This
increased fertility of the ground by calcination or charring, and its
continuing to operate so many years is well worth the attention of the
farmer, and shews the use of paring and burning new turf in agriculture,
which produces its effect not so much by the ashes of the vegetable
fibres as by charring the soil which adheres to them.
These situations, whether from eminence or from moisture, which were
proper once to attract and discharge a thunder-cloud, are more liable
again to experience the same. Hence many fairy-rings are often seen near
each other either without intersecting each other, as I saw this summer
in a garden in Nottinghamshire, or intersecting each other as described
on Arthur's seat near Edinburgh in the Edinb. Trans. Vol. II. p. 3.
NOTE XIV.--BUDS AND BULBS.
_Where dwell my vegetative realms benumb'd
In buds imprison'd, or in bulbs intomb'd._
CANTO I. l. 459.
A tree is properly speaking a family or swarm of buds, each bud being an
individual plant, for if one of these buds be torn or cut out and
planted in the earth with a glass cup inverted over it to prevent its
exhalation from being at first greater than its power of absorption, it
will produce a tree similar to its parent; each bud has a leaf, which is
its lungs, appropriated to it, and the bark of the tree is a congeries
of the roots of these individual buds, whence old hollow trees are often
seen to have some branches flourish with vigour after the internal wood
is almost intirely decayed and vanished. According to this idea Linneus
has observed that trees and shrubs are roots above ground, for if a tree
be inverted leaves will grow from the root-part and roots from the
trunk-part. Phil. Bot p. 39. Hence it appears that vegetables have two
methods of propagating themselves, the oviparous as by seeds, and the
viviparous as by their buds and bulbs, and that the individual plants,
whether from seeds or buds or bulbs, are all annual productions like
many kinds of insects as the silk-worm, the parent perishing in the
autumn after having produced an embryon, which lies in a torpid state
during the winter, and is matured in the succeeding summer. Hence
Linneus names buds and bulbs the winter-cradles of the plant or
hybernacula, and might have given the same term to seeds. In warm
climates few plants produce buds, as the vegetable life can be
compleated in one summer, and hence the hybernacle is not wanted; in
cold climates also some plants do not produce buds, as philadelphus,
frangula, viburnum, ivy, heath, wood-nightshade, rue, geranium.
The bulbs of plants are another kind of winter-cradle, or hybernacle,
adhering to the descending trunk, and are found in the perennial
herbaceous plants which are too tender to bear the cold of the winter.
The production of these subterraneous winter lodges, is not yet perhaps
clearly understood, they have been distributed by Linneus according to
their forms into scaly, solid, coated, and jointed bulbs, which however
does not elucidate their manner of production. As the buds of trees may
be truly esteemed individual annual plants, their roots constituting the
bark of the tree, it follows that these roots (viz. of each individual
bud) spread themselves over the last years bark, making a new bark over
the old one, and thence descending cover with a new bark the old roots
also in the same manner. A similar circumstance I suppose to happen in
some herbaceous plants, that is, a new bark is annually produced over
the old root, and thus for some years at least the old root or caudex
increases in size and puts up new stems. As these roots increase in size
the central part I suppose changes like the internal wood of a tree and
does not possess any vegetable life, and therefore gives out no fibres
or rootlets, and hence appears bitten off, as in valerian, plantain, and
devil's-bit. And this decay of the central part of the root I suppose
has given occasion to the belief of the root-fibres drawing down the
bulb so much insisted on by Mr. Milne in his Botanical Dictionary, Art.
Bulb.
From the observations and drawings of various kinds of bulbous roots at
different times of their growth, sent me by a young lady of nice
observation, it appears probable that all bulbous roots properly so
called perish annually in this climate: Bradley, Miller, and the Author
of Spectacle de la Nature, observe that the tulip annually renews its
bulb, for the stalk of the old flower is found under the old dry coat
but on the outside of the new bulb. This large new bulb is the flowering
bulb, but besides this there are other small new bulbs produced between
the coats of this large one but from the same caudex, (or circle from
which the root-fibres spring;) these small bulbs are leaf-bearing bulbs,
and renew themselves annually with increasing size till they bear
flowers.
Miss ---- favoured me with the following curious experiment: She took a
small tulip-root out of the earth when the green leaves were
sufficiently high to show the flower, and placed it in a glass of water;
the leaves and flower soon withered and the bulb became wrinkled and
soft, but put out one small side bulb and three bulbs beneath descending
an inch into the water by long processes from the caudex, the old bulb
in some weeks intirely decayed; on dissecting this monster, the middle
descending bulb was found by its process to adhere to the caudex and to
the old flower-stem, and the side ones were separated from the flower-
stem by a few shrivelled coats but adhered to the caudex. Whence she
concludes that these last were off-sets or leaf-bulbs which should have
been seen between the coats of the new flower-bulb if it had been left
to grow in the earth, and that the middle one would have been the new
flower-bulb. In some years (perhaps in wet seasons) the florists are
said to lose many of their tulip-roots by a similar process, the new
leaf-bulbs being produced beneath the old ones by an elongation of the
caudex without any new flower-bulbs.
By repeated dissections she observes that the leaf-bulbs or off-sets of
tulip, crocus, gladiolus, fritillary, are renewed in the same manner as
the flowering-bulbs, contrary to the opinion of many writers; this new
leaf-bulb is formed on the inside of the coats from whence the leaves
grow, and is more or less advanced in size as the outer coats and leaves
are more or less shrivelled. In examining tulip, iris, hyacinth, hare-
bell, the new bulb was invariably found _between_ the flower-stem and
the base of the innermost leaf of those roots which had flowered, and
_inclosed_ by the base of the innermost leaf in those roots which had
not flowered, in both cases adhering to the caudex or fleshy circle from
which the root-fibres spring.
Hence it is probable that the bulbs of hyacinths are renewed annually,
but that this is performed from the caudex within the old bulb, the
outer coat of which does not so shrivel as in crocus and fritillary and
hence this change is not so apparent. But I believe as soon as the
flower is advanced the new bulbs may be seen on dissection, nor does the
annual increase of the size of the root of cyclamen and of aletris
capensis militate against this annual renewal of them, since the leaf-
bulbs or off-sets, as described above, are increased in size as they are
annually renewed. See note on orchis, and on anthoxanthum, in Vol. II.
of this work.
NOTE XV.--SOLAR VOLCANOS.
_From the deep craters of his realms of fire
The whirling sun this ponderous planet hurld_.
CANTO II. l. 14.
Dr. Alexander Wilson, Professor of Astronomy at Glasgow, published a
paper in the Philosophical Transactions for 1774, demonstrating that the
spots in the sun's disk are real cavities, excavations through the
luminous material, which covers the other parts of the sun's surface.
One of these cavities he found to be about 4000 miles deep and many
times as wide. Some objections were made to this doctrine by M. De la
Laude in the Memoirs of the French Academy for the year 1776, which
however have been ably answered by Professor Wilson in reply in the
Philos. Trans. for 1783. Keil observes, in his Astronomical Lectures, p.
44, "We frequently see spots in the sun which are larger and broader not
only than Europe or Africa, but which even equal, if they do not exceed,
the surface of the whole terraqueous globe." Now that these cavities are
made in the sun's body by a process of nature similar to our earthquakes
does not seem improbable on several accounts. 1. Because from this
discovery of Dr. Wilson it appears that the internal parts of the sun
are not in a state of inflammation or of ejecting light, like the
external part or luminous ocean which covers it; and hence that a
greater degree of heat or inflammation and consequent expansion or
explosion may occasionally be produced in its internal or dark nucleus.
2. Because the solar spots or cavities are frequently increased or
diminished in size. 3. New ones are often produced. 4. And old ones
vanish. 5. Because there are brighter or more luminous parts of the
sun's disk, called faculae by Scheiner and Hevelius, which would seem to
be volcanos in the sun, or, as Dr. Wilson calls them, "eructations of
matter more luminous than that which covers the sun's surface." 6. To
which may be added that all the planets added together with their
satellites do not amount to more than one six hundred and fiftieth part
of the mass of the sun according to Sir Isaac Newton.
Now if it could be supposed that the planets were originally thrown out
of the sun by larger sun-quakes than those frequent ones which occasion
these spots or excavations above-mentioned, what would happen? 1.
According to the observations and opinion of Mr. Herschel the sun itself
and all its planets are moving forwards round some other centre with an
unknown velocity, which may be of opake matter corresponding with the
very antient and general idea of a chaos. Whence if a ponderous planet,
as Saturn, could be supposed to be projected from the sun by an
explosion, the motion of the sun itself might be at the same time
disturbed in such a manner as to prevent the planet from falling again
into it. 2. As the sun revolves round its own axis its form must be that
of an oblate spheroid like the earth, and therefore a body projected
from its surface perpendicularly upwards from that surface would not
rise perpendicularly from the sun's centre, unless it happened to be
projected exactly from either of its poles or from its equator. Whence
it may not be necessary that a planet if thus projected from the sun by
explosion should again fall into the sun. 3. They would part from the
sun's surface with the velocity with which that surface was moving, and
with the velocity acquired by the explosion, and would therefore move
round the sun in the same direction in which the sun rotates on its
axis, and perform eliptic orbits. 4. All the planets would move the same
way round the sun, from this first motion acquired at leaving its
surface, but their orbits would be inclined to each other according to
the distance of the part, where they were thrown out, from the sun's
equator. Hence those which were ejected near the sun's equator would
have orbits but little inclined to each other, as the primary planets;
the plain of all whose orbits are inclined but seven degrees and a half
from each other. Others which were ejected near the sun's poles would
have much more eccentric orbits, as they would partake so much less of
the sun's rotatory motion at the time they parted from his surface, and
would therefore be carried further from the sun by the velocity they had
gained by the explosion which ejected them, and become comets. 5. They
would all obey the same laws of motion in their revolutions round the
sun; this has been determined by astronomers, who have demonstrated that
they move through equal areas in equal times. 6. As their annual periods
would depend on the height they rose by the explosion, these would
differ in them all. 7. As their diurnal revolutions would depend on one
side of the exploded matter adhering more than the other at the time it
was torn off by the explosion, these would also differ in the different
planets, and not bear any proportion to their annual periods. Now as all
these circumstances coincide with the known laws of the planetary
system, they serve to strengthen this conjecture.
This coincidence of such a variety of circumstances induced M. de Buffon
to suppose that the planets were all struck off from the sun's surface
by the impact of a large comet, such as approached so near the sun's
disk, and with such amazing velocity, in the year 1680, and is expected
to return in 2255. But Mr. Buffon did not recollect that these comets
themselves are only planets with more eccentric orbits, and that
therefore it must be asked, what had previously struck off these comets
from the sun's body? 2. That if all these planets were struck off from
the sun at the same time, they must have been so near as to have
attracted each other and have formed one mass: 3. That we shall want new
causes for separating the secondary planets from the primary ones, and
must therefore look out for some other agent, as it does not appear how
the impulse of a comet could have made one planet roll round another at
the time they both of them were driven off from the surface of the sun.
If it should be asked, why new planets are not frequently ejected from
the sun? it may be answered, that after many large earthquakes many
vents are left for the elastic vapours to escape, and hence, by the
present appearance of the surface of our earth, earthquakes prodigiously
larger than any recorded in history have existed; the same circumstances
may have affected the sun, on whose surface there are appearances of
volcanos, as described above. Add to this, that some of the comets, and
even the georgium sidus, may, for ought we know to the contrary, have
been emitted from the sun in more modern days, and have been diverted
from their course, and thus prevented from returning into the sun, by
their approach to some of the older planets, which is somewhat
countenanced by the opinion several philosophers have maintained, that
the quantity of matter of the sun has decreased. Dr. Halley observed,
that by comparing the proportion which the periodical time of the moon
bore to that of the sun in former times, with the proportion between
them at present, that the moon is found to be somewhat accelerated in
respect to the sun. Pemberton's View of Sir Isaac Newton, p. 247. And so
large is the body of this mighty luminary, that all the planets thus
thrown out of it would make scarcely any perceptible diminution of it,
as mentioned above. The cavity mentioned above, as measured by Dr.
Wilson of 4000 miles in depth, not penetrating an hundredth part of the
sun's semi-diameter; and yet, as its width was many times greater than
its depth, was large enough to contain a greater body than our
terrestrial world.
I do not mean to conceal, that from the laws of gravity unfolded by Sir
Isaac Newton, supposing the sun to be a sphere and to have no
progressive motion, and not liable itself to be disturbed by the
supposed projection of the planets from it, that such planets must
return into the sun. The late Rev. William Ludlam, of Leicester, whose
genius never met with reward equal to its merits, in a letter to me,
dated January, 1787, after having shewn, as mentioned above, that
planets so projected from the sun would return to it, adds, "That a body
as large as the moon so projected, would disturb the motion of the earth
in its orbit, is certain; but the calculation of such disturbing forces
is difficult. The body in some circumstances might become a satellite,
and both move round their common centre of gravity, and that centre be
carried in an annual orbit round the sun."
There are other circumstances which might have concurred at the time of
such supposed explosions, which would render this idea not impossible.
1. The planets might be thrown out of the sun at the time the sun itself
was rising from chaos, and be attracted by other suns in their vicinity
rising at the same time out of chaos, which would prevent them from
returning into the sun. 2. The new planet in its course or ascent from
the sun, might explode and eject a satellite, or perhaps more than one,
and thus by its course being affected might not return into the sun. 3.
If more planets were ejected at the same time from the sun, they might
attract and disturb each others course at the time they left the body of
the sun, or very soon afterwards, when they would be so much nearer each
other.
NOTE XVI.--CALCAREOUS EARTH.
_While Ocean wrap'd it in his azure robe_.
CANTO II. l. 34.
From having observed that many of the highest mountains of the world
consist of lime-stone replete with shells, and that these mountains bear
the marks of having been lifted up by subterraneous fires from the
interior parts of the globe; and as lime-stone replete with shells is
found at the bottom of many of our deepest mines some philosophers have
concluded that the nucleus of the earth was for many ages covered with
water which was peopled with its adapted animals; that the shells and
bones of these animals in a long series of time produced solid strata in
the ocean surrounding the original nucleus.
These strata consist of the accumulated exuviae of shell-fish, the
animals perished age after age but their shells remained, and in
progression of time produced the amazing quantities of lime-stone which
almost cover the earth. Other marine animals called coralloids raised
walls and even mountains by the congeries of their calcareous
habitations, these perpendicular corralline rocks make some parts of the
Southern Ocean highly dangerous, as appears in the journals of Capt.
Cook. From contemplating the immense strata of lime-stone, both in
respect to their extent and thickness, formed from these shells of
animals, philosophers have been led to conclude that much of the water
of the sea has been converted into calcareous earth by passing through
their organs of digestion. The formation of calcareous earth seems more
particularly to be an animal process as the formation of clay belongs to
the vegetable economy; thus the shells of crabs and other testaceous
fish are annually reproduced from the mucous membrane beneath them; the
shells of eggs are first a mucous membrane, and the calculi of the
kidneys and those found in all other parts of our system which sometimes
contain calcareous earth, seem to originate from inflamed membranes; the
bones themselves consist of calcareous earth united with the phosphoric
or animal acid, which may be separated by dissolving the ashes of
calcined bones in the nitrous acid; the various secretions of animals,
as their saliva and urine, abound likewise with calcareous earth, as
appears by the incrustations about the teeth and the sediments of urine.
It is probable that animal mucus is a previous process towards the
formation of calcareous earth; and that all the calcareous earth in the
world which is seen in lime-stones, marbles, spars, alabasters, marls,
(which make up the greatest part of the earth's crust, as far as it has
yet been penetrated,) have been formed originally by animal and
vegetable bodies from the mass of water, and that by these means the
solid part of the terraqueous globe has perpetually been in an
increasing state and the water perpetually in a decreasing one.
After the mountains of shells and other recrements of aquatic animals
were elevated above the water the upper heaps of them were gradually
dissolved by rains and dews and oozing through were either perfectly
crystallized in smaller cavities and formed calcareous spar, or were
imperfectly crystallized on the roofs of larger cavities and produced
stalactes; or mixing with other undissolved shells beneath them formed
marbles, which were more or less crystallized and more or less pure; or
lastly, after being dissolved, the water was exhaled from them in such a
manner that the external parts became solid, and forming an arch
prevented the internal parts from approaching each other so near as to
become solid, and thus chalk was produced. I have specimens of chalk
formed at the root of several stalactites, and in their central parts;
and of other stalactites which are hollow like quills from a similar
cause, viz. from the external part of the stalactite hardening first by
its evaporation, and thus either attracting the internal dissolved
particles to the crust, or preventing them from approaching each other
so as to form a solid body. Of these I saw many hanging from the arched
roof of a cellar under the high street in Edinburgh.
If this dissolved limestone met with vitriolic acid it was converted
into alabaster, parting at the same time with its fixable air. If it met
with the fluor acid it became fluor; if with the siliceous acid, flint;
and when mixed with clay and sand, or either of them, acquires the name
of marl. And under one or other of these forms composes a great part of
the solid globe of the earth.
Another mode in which limestone appears is in the form of round
granulated particles, but slightly cohering together; of this kind a bed
extends over Lincoln heath, perhaps twenty miles long by ten wide. The
form of this calcareous sand, its angles having been rubbed off, and the
flatness of its bed, evinces that that part of the country was so formed
under water, the particles of sand having thus been rounded, like all
other rounded pebbles. This round form of calcareous sand and of other
larger pebbles is produced under water, partly by their being more or
less soluble in water, and hence the angular parts become dissolved,
first, by their exposing a larger surface to the action of the
menstruum, and secondly, from their attrition against each other by the
streams or tides, for a great length of time, successively as they were
collected, and perhaps when some of them had not acquired their hardest
state.
This calcareous sand has generally been called ketton-stone and believed
to resemble the spawn of fish, it has acquired a form so much rounder
than siliceous sand from its being of so much softer a texture and also
much more soluble in water. There are other soft calcareous stones
called tupha which are deposited from water on mosses, as at Matlock,
from which moss it is probable the water may receive something which
induces it the readier to part with its earth.
In some lime-stones the living animals seem to have been buried as well
as their shells during some great convulsion of nature, these shells
contain a black coaly substance within them, in others some phlogiston
or volatile alcali from the bodies of the dead animals remains mixed
with the stone, which is then called liver-stone as it emits a
sulphurous smell on being struck, and there is a stratum about six
inches thick extends a considerable way over the iron ore at Wingerworth
near Chesterfield in Derbyshire which seems evidently to have been
formed from the shells of fresh-water muscles.
There is however another source of calcareous earth besides the aquatic
one above described and that is from the recrements of land animals and
vegetables as found in marls, which consist of various mixtures of
calcareous earth, sand, and clay, all of them perhaps principally from
vegetable origin.
Dr. Hutton is of opinion that the rocks of marble have been softened by
fire into a fluid mass, which he thinks under immense pressure might be
done without the escape of their carbonic acid or fixed air. Edinb.
Transact. Vol. I. If this ingenious idea be allowed it might account for
the purity of some white marbles, as during their fluid state there
might be time for their partial impurities, whether from the bodies of
the animals which produced the shells or from other extraneous matter,
either to sublime to the uppermost part of the stratum or to subside to
the lowermost part of it. As a confirmation of this theory of Dr.
Hutton's it may be added that some calcareous stones are found mixed
with lime, and have thence lost a part of their fixed air or carbonic
gas, as the bath-stone, and on that account hardens on being exposed to
the air, and mixed with sulphur produces calcareous liver of sulphur.
Falconer on Bath-water. Vol. I. p. 156. and p. 257. Mr. Monnet found
lime in powder in the mountains of Auvergne, and suspected it of
volcanic origin. Kirwan's Min. p. 22.
NOTE XVII.--MORASSES.
_Gnomes! you then taught transuding dews to pass
Through time-fallen woods, and root-inwove morass_.
CANTO II. l. 115.
Where woods have repeatedly grown and perished morasses are in process
of time produced, and by their long roots fill up the interstices till
the whole becomes for many yards deep a mass of vegetation. This fact is
curiously verified by an account given many years ago by the Earl of
Cromartie, of which the following is a short abstract.
In the year 1651 the EARL OF CROMARTIE being then nineteen years of age
saw a plain in the parish of Lockburn covered over with a firm standing
wood, which was so old that not only the trees had no green leaves upon
them but the bark was totally thrown off, which he was there informed by
the old countrymen was the universal manner in which fir-woods
terminated, and that in twenty or thirty years the trees would cast
themselves up by the roots. About fifteen years after he had occasion to
travel the same way and observed that there was not a tree nor the
appearance of a root of any of them; but in their place the whole plain
where the wood stood was covered with a flat green moss or morass, and
on asking the country people what was become of the wood he was informed
that no one had been at the trouble to carry it away, but that it had
all been overturned by the wind, that the trees lay thick over each
other, and that the moss or bog had overgrown the whole timber, which
they added was occasioned by the moisture which came down from the high
hills above it and stagnated upon the plain, and that nobody could yet
pass over it, which however his Lordship was so incautious as to attempt
and slipt up to the arm-pits. Before the year 1699 that whole piece of
ground was become a solid moss wherein the peasants then dug turf or
peat, which however was not yet of the best sort. Philos. Trans. No.
330. Abridg. Vol. V. p. 272.
Morasses in great length of time undergo variety of changes, first by
elutriation, and afterwards by fermentation, and the consequent heat. 1.
By water perpetually oozing through them the most soluble parts are
first washed away, as the essential salts, these together with the salts
from animal recrements are carried down the rivers into the sea, where
all of them seem to decompose each other except the marine salt. Hence
the ashes of peat contain little or no vegetable alcali and are not used
in the countries, where peat constitutes the fuel of the lower people,
for the purpose of washing linen. The second thing which is always seen
oozing from morasses is iron in solution, which produces chalybeate
springs, from whence depositions of ochre and variety of iron ores. The
third elutriation seems to consist of vegetable acid, which by means
unknown appears to be converted into all other acids. 1. Into marine and
nitrous acids as mentioned above. 2. Into vitriolic acid which is found
in some morasses so plentifully as to preserve the bodies of animals
from putrefaction which have been buried in them, and this acid carried
away by rain and dews and meeting with calcareous earth produces gypsum
or alabaster, with clay it produces alum, and deprived of its vital air
produces sulphur. 3. Fluor acid which being washed away and meeting with
calcareous earth produces fluor or cubic spar. 4. The siliceous acid
which seems to have been disseminated in great quantity either by
solution in water or by solution in air, and appears to have produced
the sand in the sea uniting with calcareous earth previously dissolved
in that element, from which were afterwards formed some of the grit-
stone rocks by means of a siliceous or calcareous cement. By its union
with the calcareous earth of the morass other strata of siliceous sand
have been produced; and by the mixture of this with clay and lime arose
the beds of marl.
In other circumstances, probably where less moisture has prevailed,
morasses seem to have undergone a fermentation, as other vegetable
matter, new hay for instance is liable to do from the great quantity of
sugar it contains. From the great heat thus produced in the lower parts
of immense beds of morass the phlogistic part, or oil, or asphaltum,
becomes distilled, and rising into higher strata becomes again condensed
forming coal-beds of greater or less purity according to their greater
or less quantity of inflammable matter; at the same time the clay beds
become purer or less so, as the phlogistic part is more or less
completely exhaled from them. Though coal and clay are frequently
produced in this manner, yet I have no doubt, but that they are likewise
often produced by elutriation; in situations on declivities the clay is
washed away down into the valleys, and the phlogistic part or coal left
behind; this circumstance is seen in many valleys near the beds of
rivers, which are covered recently by a whitish impure clay, called
water-clay. See note XIX. XX. and XXIII.
LORD CROMARTIE has furnished another curious observation on morasses in
the paper above referred to. In a moss near the town of Eglin in Murray,
though there is no river or water which communicates with the moss, yet
for three or four feet of depth in the moss there are little shell-fish
resembling oysters with living fish in them in great quantities, though
no such fish are found in the adjacent rivers, nor even in the water
pits in the moss, but only in the solid substance of the moss. This
curious fact not only accounts for the shells sometimes found on the
surface of coals, and in the clay above them; but also for a thin
stratum of shells which sometimes exists over iron-ore.
NOTE XVIII.--IRON.
_Cold waves, immerged, the glowing mass congeal,
And turn to adamant the hissing Steel._
CANTO II. l. 191.
As iron is formed near the surface of the earth, it becomes exposed to
streams of water and of air more than most other metallic bodies, and
thence becomes combined with oxygene, or vital air, and appears very
frequently in its calciform state, as in variety of ochres. Manganese,
and zinc, and sometimes lead, are also found near the surface of the
earth, and on that account become combined with vital air and are
exhibited in their calciform state.
The avidity with which iron unites with oxygene, or vital air, in which
process much heat is given out from the combining materials, is shewn by
a curious experiment of M. Ingenhouz. A fine iron wire twisted spirally
is fixed to a cork, on the point of the spire is fixed a match made of
agaric dipped in solution of nitre; the match is then ignited, and the
wire with the cork put immediately into a bottle full of vital air, the
match first burns vividly, and the iron soon takes fire and consumes
with brilliant sparks till it is reduced to small brittle globules,
gaining an addition of about one third of its weight by its union, with
vital air. Annales de Chymie. Traité de Chimie, per Lavoisier, c. iii.
STEEL.
It is probably owing to a total deprivation of vital air which it holds
with so great avidity, that iron on being kept many hours or days in
ignited charcoal becomes converted into steel, and thence acquires the
faculty of being welded when red hot long before it melts, and also the
power of becoming hard when immersed in cold water; both which I suppose
depend on the same cause, that is, on its being a worse conductor of
heat than other metals; and hence the surface both acquires heat much
sooner, and loses it much sooner, than the internal parts of it, in this
circumstance resembling glass.
When steel is made very hot, and suddenly immerged in very cold water,
and moved about in it, the surface of the steel becomes cooled first,
and thus producing a kind of case or arch over the internal part,
prevents that internal part from contracting quite so much as it
otherwise would do, whence it becomes brittler and harder, like the
glass-drops called Prince Rupert's drops, which are made by dropping
melted glass into cold water. This idea is countenanced by the
circumstance that hardened steel is specifically lighter than steel
which is more gradually cooled. (Nicholson's Chemistry, p. 313.) Why the
brittleness and hardness of steel or glass should keep pace or be
companions to each other may be difficult to conceive.
When a steel spring is forcibly bent till it break, it requires less
power to bend it through the first inch than the second, and less
through the second than the third; the same I suppose to happen if a
wire be distended till it break by hanging weights to it; this shews
that the particles may be forced from each other to a small distance by
less power, than is necessary to make them recede to a greater distance;
in this circumstance perhaps the attraction of cohesion differs from
that of gravitation, which exerts its power inversely as the squares of
the distance. Hence it appears that if the innermost particles of a
steel bar, by cooling the external surface first, are kept from
approaching each other so nearly as they otherwise would do, that they
become in the situation of the particles on the convex side of a bent
spring, and can not be forced further from each other except by a
greater power than would have been necessary to have made them recede
thus far. And secondly, that if they be forced a little further from
each other they separate; this may be exemplified by laying two magnetic
needles parallel to each other, the contrary poles together, then
drawing them longitudinally from each other, they will slide with small
force till they begin to separate, and will then require a stronger
force to really separate them. Hence it appears, that hardness and
brittleness depend on the same circumstance, that the particles are
removed to a greater distance from each other and thus resist any power
more forcibly which is applied to displace them further, this
constitutes hardness. And secondly, if they are displaced by such
applied force they immediately separate, and this constitutes
brittleness.
Steel may be thus rendered too brittle for many purposes, on which
account artists have means of softening it again, by exposing it to
certain degrees of heat, for the construction of different kinds of
tools, which is called tempering it. Some artists plunge large tools in
very cold water as soon as they are compleatly ignited, and moving it
about, take it out as soon as it ceases to be luminous beneath the
water; it is then rubbed quickly with a file or on sand to clean the
surface, the heat which the metal still retains soon begins to produce a
succession of colours; if a hard temper be required, the piece is dipped
again and stirred about in cold water as soon as the yellow tinge
appears, if it be cooled when the purple tinge appears it becomes fit
for gravers' tools used in working upon metals; if cooled while blue it
is proper for springs. Nicholson's Chemistry, p. 313. Keir's Chemical
Dictionary.
MODERN PRODUCTION OF IRON.
The recent production of iron is evinced from the chalybeate waters
which flow from morasses which lie upon gravel-beds, and which must
therefore have produced iron after those gravel-beds were raised out of
the sea. On the south side of the road between Cheadle and Okeymoor in
Staffordshire, yellow stains of iron are seen to penetrate the gravel
from a thin morass on its surface. There is a fissure eight or ten feet
wide, in a gravel-bed on the eastern side of the hollow road ascending
the hill about a mile from Trentham in Staffordshire, leading toward
Drayton in Shropshire, which fissure is filled up with nodules of iron-
ore. A bank of sods is now raised against this fissure to prevent the
loose iron nodules from falling into the turnpike road, and thus this
natural curiosity is at present concealed from travellers. A similar
fissure in a bed of marl, and filled up with iron nodules and with some
large pieces of flint, is seen on the eastern side of the hollow road
ascending the hill from the turnpike house about a mile from Derby in
the road towards Burton. And another such fissure filled with iron
nodes, appears about half a mile from Newton-Solney in Derbyshire, in
the road to Burton, near the summit of the hill. These collections of
iron and of flint must have been produced posterior to the elevation of
all those hills, and were thence evidently of vegetable or animal
origin. To which should be added, that iron is found in general in beds
either near the surface of the earth, or stratified with clay coals or
argillaceous grit, which are themselves productions of the modern world,
that is, from the recrements of vegetables and air-breathing animals.
Not only iron but manganese, calamy, and even copper and lead appear in
some instances to have been of recent production. Iron and manganese are
detected in all vegetable productions, and it is probable other metallic
bodies might be found to exist in vegetable or animal matters, if we had
tests to detect them in very minute quantities. Manganese and calamy are
found in beds like iron near the surface of the earth, and in a
calciform state, which countenances their modern production. The recent
production of calamy, one of the ores of zinc, appears from its
frequently incrusting calcareous spar in its descent from the surface of
the earth into the uppermost fissures of the limestone mountains of
Derbyshire. That the calamy has been carried by its solution or
diffusion in water into these cavities, and not by its ascent from below
in form of steam, is evinced from its not only forming a crust over the
dogtooth spar, but by its afterwards dissolving or destroying the sparry
crystal. I have specimens of calamy in the form of dogtooth spar, two
inches high, which are hollow, and stand half an inch above the
diminished sparry crystal on which they were formed, like a sheath a
great deal too big for it; this seems to shew, that this process was
carried on in water, otherwise after the calamy had incrusted its spar,
and dissolved its surface, so as to form a hollow cavern over it, it
could not act further upon it except by the interposition of some
medium. As these spars and calamy are formed in the fissures of
mountains they must both have been formed after the elevation of those
mountains.
In respect to the recent production of copper, it was before observed in
note on Canto II. l. 394, that the summit of the grit-stone mountain at
Hawkstone in Shropshire, is tinged with copper, which from the
appearance of the blue stains seems to have descended to the parts of
the rock beneath. I have a calciform ore of copper consisting of the
hollow crusts of cubic cells, which has evidently been formed on
crystals of fluor, which it has eroded in the same manner as the calamy
erodes the calcareous crystals, from whence may be deduced in the same
manner, the aqueous solution or diffusion, as well as the recent
production of this calciform ore of copper.
Lead in small quantities is sometimes found in the fissures of coal-
beds, which fissures are previously covered with spar; and sometimes in
nodules of iron-ore. Of the former I have a specimen from near Caulk in
Derbyshire, and of the latter from Colebrook Dale in Shropshire. Though
all these facts shew that some metallic bodies are formed from vegetable
or animal recrements, as iron, and perhaps manganese and calamy, all
which are found near the surface of the earth; yet as the other metals
are found only in fissures of rocks, which penetrate to unknown depths,
they may be wholly or in part produced by ascending steams from
subterraneous fires, as mentioned in note on Canto II. l. 398.
SEPTARIA OF IRON-STONE.
Over some lime works at Walsall in Staffordshire, I observed some years
ago a stratum of iron earth about six inches thick, full of very large
cavities; these cavities were evidently produced when the material
passed from a semifluid state into a solid one; as the frit of the
potters, or a mixture of clay and water is liable to crack in drying;
which is owing to the further contraction of the internal part, after
the crust is become hard. These hollows are liable to receive extraneous
matter, as I believe gypsum, and sometimes spar, and even lead; a
curious specimen of the last was presented to me by Mr. Darby of
Colebrook Dale, which contains in its cavity some ounces of lead-ore.
But there are other septaria of iron-stone which seem to have had a very
different origin, their cavities having been formed in cooling or
congealing from an ignited state, as is ingeniously deduced by Dr.
Hutton from their internal structure. Edinb. Transact. Vol. I. p. 246.
The volcanic origin of these curious septaria appears to me to be
further evinced from their form and the places where they are found.
They consist of oblate spheroids and are found in many parts of the
earth totally detached from the beds in which they lie, as at East
Lothian in Scotland. Two of these, which now lie before me, were found
with many others immersed in argillaceous shale or shiver, surrounded by
broken limestone mountains at Bradbourn near Ashbourn in Derbyshire, and
were presented to me by Mr. Buxton, a gentleman of that town. One of
these is about fifteen inches in its equatorial diameter, and about six
inches in its polar one, and contains beautiful star-like septaria
incrusted and in part filled with calcareous spar. The other is about
eight inches in its equatorial diameter, and about four inches in its
polar diameter, and is quite solid, but shews on its internal surface
marks of different colours, as if a beginning separation had taken
place. Now as these septaria contain fifty per cent, of iron, according
to Dr. Hutton, they would soften or melt into a semifluid globule by
subterraneous fire by less heat than the limestone in their vicinity;
and if they were ejected through a hole or fissure would gain a circular
motion along with their progressive one by their greater friction or
adhesion to one side of the hole. This whirling motion would produce the
oblate spheroidical form which they possess, and which as far as I know
can not in any other way be accounted for. They would then harden in the
air as they rose into the colder parts of the atmosphere; and as they
descended into so soft a material as shale or shiver, their forms would
not be injured in their fall; and their presence in materials so
different from themselves becomes accounted for.
About the tropics of the large septarium above mentioned, are circular
eminent lines, such as might have been left if it had been coarsely
turned in a lathe. These lines seem to consist of a fluid matter, which
seems to have exsuded in circular zones, as their edges appear blunted
or retracted; and the septarium seems to have split easier in such
sections parallel to its equator. Now as the crust would first begin to
cool and harden after its ejection in a semifluid state, and the
equatorial diameter would become gradually enlarged as it rose in the
air; the internal parts being softer would slide beneath the polar
crust, which might crack and permit part of the semifluid to exsude, and
it is probable the adhesion would thus become less in sections parallel
to the equator. Which further confirms this idea of the production of
these curious septaria. A new-cast cannon ball red-hot with its crust
only solid, if it were shot into the air would probably burst in its
passage; as it would consist of a more fluid material than these
septaria; and thus by discharging a shower of liquid iron would produce
more dreadful combustion, if used in war, than could be effected by a
ball, which had been cooled and was heated again: since in the latter
case the ball could not have its internal parts made hotter than the
crust of it, without first loosing its form.
NOTE XIX.--FLINT.
_Transmute to glittering flints her chalky lands,
Or sink on Ocean's bed in countless sands._
CANTO II. l. 217.
1. SILICEOUS ROCKS.
The great masses of siliceous sand which lie in rocks upon the beds of
limestone, or which are stratified with clay, coal, and iron-ore, are
evidently produced in the decomposition of vegetable or animal matters,
as explained in the note on morasses. Hence the impressions of vegetable
roots and even whole trees are often found in sand-stone, as well as in
coals and iron-ore. In these sand-rocks both the siliceous acid and the
calcareous base seem to be produced from the materials of the morass;
for though the presence of a siliceous acid and of a calcareous base
have not yet been separately exhibited from flints, yet from the analogy
of flint to fluor, and gypsum, and marble, and from the conversion of
the latter into flint, there can be little doubt of their existence.
These siliceous sand-rocks are either held together by a siliceous
cement, or have a greater or less portion of clay in them, which in some
acts as a cement to the siliceous crystals, but in others is in such
great abundance that in burning them they become an imperfect porcelain
and are then used to repair the roads, as at Chesterfield in Derbyshire;
these are called argillaceous grit by Mr. Kirwan. In other places a
calcareous matter cements the crystals together; and in other places the
siliceous crystals lie in loose strata under the marl in the form of
white sand; as at Normington about a mile from Derby.
The lowest beds of siliceous sand-stone produced from morasses seem to
obtain their acid from the morass, and their calcareous base from the
limestone on which it rests; These beds possess a siliceous cement, and
from their greater purity and hardness are used for course grinding-
stones and scyth stones, and are situated on the edges of limestone
countries, having lost the other strata of coals, or clay, or iron,
which were originally produced above them. Such are the sand-rocks
incumbent on limestone near Matlock in Derbyshire. As these siliceous
sand-rocks contain no marine productions scattered amongst them, they
appear to have been elevated, torn to pieces, and many fragments of them
scattered over the adjacent country by explosions, from fires within the
morass from which they have been formed; and which dissipated every
thing inflammable above and beneath them, except some stains of iron,
with which they are in some places spotted. If these sand-rocks had been
accumulated beneath the sea, and elevated along with the beds of
limestone on which they rest, some vestiges of marine shells either in
their siliceous or calcareous state must have been discerned amongst
them.
2. SILICEOUS TREES.
In many of these sand-rocks are found the impressions of vegetable
roots, which seem to have been the most unchangeable parts of the plant,
as shells and shark's teeth are found in chalk-beds from their being the
most unchangeable parts of the animal. In other instances the wood
itself is penetrated, and whole trees converted into flint; specimens of
which I have by me, from near Coventry, and from a gravel-pit in
Shropshire near Child's Archal in the road to Drayton. Other polished
specimens of vegetable flints abound in the cabinets of the curious,
which evidently shew the concentric circles of woody fibres, and their
interstices filled with whiter siliceous matter, with the branching off
of the knots when cut horizontally, and the parallel lines of wood when
cut longitudinally, with uncommon beauty and variety. Of these I possess
some beautiful specimens, which were presented to me by the Earl of
Uxbridge.
The colours of these siliceous vegetables are generally brown, from the
iron, I suppose, or manganese, which induced them to crystallize or to
fuse more easily. Some of the cracks of the wood in drying are filled
with white flint or calcedony, and others of them remain hollow, lined
with innumerable small crystals tinged with iron, which I suppose had a
share in converting their calcareous matter into siliceous crystals,
because the crystals called Peak-diamonds are always found bedded in an
ochreous earth; and those called Bristol-stones are situated on
limestone coloured with iron. Mr. F. French presented me with a
congeries of siliceous crystals, which he gathered on the crater (as he
supposes) of an extinguished volcano at Cromach Water in Cumberland. The
crystals are about an inch high in the shape of dogtooth or calcareous
spar, covered with a dark ferruginous matter. The bed on which they rest
is about an inch in thickness, and is stained with iron on its
undersurface. This curious fossil shews the transmutation of calcareous
earth into siliceous, as much as the siliceous shells which abound in
the cabinets of the curious. There may sometime be discovered in this
age of science, a method of thus impregnating wood with liquid flint,
which would produce pillars for the support, and tiles for the covering
of houses, which would be uninflammable and endure as long as the earth
beneath them.
That some siliceous productions have been in a fluid state without much
heat at the time of their formation appears from the vegetable flints
above described not having quite lost their organized appearance; from
shells, and coralloids, and entrochi being converted into flint without
loosing their form; from the bason of calcedony round Giesar in Iceland;
and from the experiment of Mr. Bergman, who obtained thirteen regular
formed crystals by suffering the powder of quartz to remain in a vessel
with fluor acid for two years; these crystals were about the size of
small peas, and were not so hard as quartz. Opusc. de Terrâ Siliceâ, p.
33. Mr. Achard procured both calcareous and siliceous crystals, one from
calcareous earth, and the other from the earth of alum, both dissolved
in water impregnated with fixed air; the water filtrating very slowly
through a porous bottom of baked clay. See Journal de Physique, for
January, 1778.
3. AGATES, ONYXES, SCOTS-PEBBLES.
In small cavities of these sand-rocks, I am informed, the beautiful
siliceous nodules are found which are called Scot's-pebbles; and which
on being cut in different directions take the names of agates, onyxes,
sardonyxes, &c. according to the colours of the lines or strata which
they exhibit. Some of the nodules are hollow and filled with crystals,
others have a nucleus of less compact siliceous matter which is
generally white, surrounded with many concentric strata coloured with
iron, and other alternate strata of white agate or calcedony, sometimes
to the number of thirty.
I think these nodules bear evident marks of their having been in perfect
fusion by either heat alone, or by water and heat, under great pressure,
according to the ingenious theory of Dr. Hutton; but I do not imagine,
that they were injected into cavities from materials from without, but
that some vegetables or parts of vegetables containing more iron or
manganese than others, facilitated the compleat fusion, thus destroying
the vestiges of vegetable organization, which were conspicuous in the
siliceous trees above mentioned. Some of these nodules being hollow and
lined with crystals, and others containing a nucleus of white siliceous
matter of a looser texture, shew they were composed of the materials
then existing in the cavity; which consisting before of loose sand, must
take up less space when fused into a solid mass.
These siliceous nodules resemble the nodules of iron-stone mentioned in
note on Canto II. l. 183, in respect to their possessing a great number
of concentric spheres coloured generally with iron, but they differ in
this circumstance, that the concentric spheres generally obey the form
of the external crust, and in their not possessing a chalybeate nucleus.
The stalactites formed on the roofs of caverns are often coloured in
concentric strata, by their coats being spread over each other at
different times; and some of them, as the cupreous ones, possess great
beauty from this formation; but as these are necessarily more or less of
a cylindrical or conic form, the nodules or globular flints above
described cannot have been constructed in this manner. To what law of
nature then is to be referred the production of such numerous concentric
spheres? I suspect to the law of congelation.
When salt and water are exposed to severe frosty air, the salt is said
to be precipitated as the water freezes; that is, as the heat, in which
it was dissolved, is withdrawn; where the experiment is tried in a bowl
or bason, this may be true, as the surface freezes first, and the salt
is found at the bottom. But in a fluid exposed in a thin phial, I found
by experiment, that the extraneous matter previously dissolved by the
heat in the mixture was not simply set at liberty to subside, but was
detruded or pushed backward as the ice was produced. The experiment was
this: about two ounces of a solution of blue vitriol were accidentally
frozen in a thin phial, the glass was cracked and fallen to pieces, the
ice was dissolved, and I found a pillar of blue vitriol standing erect
on the bottom of the broken bottle. Nor is this power of congelation
more extraordinary, than that by its powerful and sudden expansion it
should burst iron shells and coehorns, or throw out the plugs with which
the water was secured in them above one hundred and thirty yards,
according to the experiments at Quebec by Major Williams. Edinb.
Transact. Vol. II. p. 23.
In some siliceous nodules which now lie before me, the external crust
for about the tenth of an inch consists of white agate, in others it is
much thinner, and in some much thicker; corresponding with this crust
there are from twenty to thirty superincumbent strata, of alternately
darker and lighter colour; whence it appears, that the external crust as
it cooled or froze, propelled from it the iron or manganese which was
dissolved in it; this receded till it had formed an arch or vault strong
enough to resist its further protrusion; then the next inner sphere or
stratum as it cooled or froze, propelled forwards its colouring matter
in the same manner, till another arch or sphere produced sufficient
resistance to this frigoriscent expulsion. Some of them have detruded
their colouring matter quite to the centre, the rings continuing to
become darker as they are nearer it; in others the chalybeate arch seems
to have stopped half an inch from the centre, and become thicker by
having attracted to itself the irony matter from the white nucleus,
owing probably to its cooling less precipitately in the central parts
than at the surface of the pebble.
A similar detrusion of a marly matter in circular arches or vaults
obtains in the salt mines in Cheshire; from whence Dr. Hutton very
ingeniously concludes, that the salt must have been liquified by heat;
which would seem to be much confirmed by the above theory. Edinb.
Transact. Vol. I. p. 244.
I cannot conclude this account of Scots-pebbles without observing that
some of them on being sawed longitudinally asunder, seem still to
possess some vestiges of the cylindrical organization of vegetables;
others possess a nucleus of white agate much resembling some bulbous
roots with their concentric coats, or the knots in elm-roots or crab-
trees; some of these I suppose were formed in the manner above
explained, during the congelation of masses of melted flint and iron;
others may have been formed from a vegetable nucleus, and retain some
vestiges of the organization of the plant.
4. SAND OF THE SEA.
The great abundance of siliceous sand at the bottom of the ocean may in
part be washed down from the siliceous rocks above described, but in
general I suppose it derives its acid only from the vegetable and animal
matter of morasses, which is carried down by floods or by the
atmosphere, and becomes united in the sea with its calcareous base from
shells and coralloids, and thus assumes its crystalline form at the
bottom of the ocean, and is there intermixed with gravel or other
matters washed from the mountains in its vicinity.
5. CHERT, OR PETROSILEX.
The rocks of marble are often alternately intermixed with strata of
chert, or coarse flint, and this in beds from one to three feet thick,
as at Ham and Matlock, or of less than the tenth of an inch in
thickness, as a mile or two from Bakewell in the road to Buxton. It is
difficult to conceive in what manner ten or twenty strata of either
limestone or flint, of different shades of white and black, could be
laid quite regularly over each other from sediments or precipitations
from the sea; it appears to me much easier to comprehend, by supposing
with Dr. Hutton, that both the solid rocks of marble and the flint had
been fused by great heat, (or by heat and water,) under immense
pressure; by its cooling or congealing the colouring matter might be
detruded, and form parallel or curvilinean strata, as above explained.
The colouring matter both of limestone and flint was probably owing to
the flesh of peculiar animals, as well as the siliceous acid, which
converted some of the limestone into flint; or to some strata of shell-
fish having been overwhelmed when alive with new materials, while others
dying in their natural situations would lose their fleshy parts, either
by its putrid solution in the water or by its being eaten by other sea-
insects. I have some calcareous fossil shells which contain a black
coaly matter in them, which was evidently the body of the animal, and
others of the same kind filled with spar instead of it. The Labradore
stone has I suppose its colours from the nacre or mother-pearl shells,
from which it was probably produced. And there is a stratum of
calcareous matter about six or eight inches thick at Wingerworth in
Derbyshire over the iron-beds, which is replete with shells of fresh-
water muscles, and evidently obtains its dark colour from them, as
mentioned in note XVI. Many nodules of flint resemble in colour as well
as in form the shell of the echinus or sea-urchin; others resemble some
coralloids both in form and colour; and M. Arduini found in the Monte de
Pancrasio, red flints branching like corals, from whence they seem to
have obtained both their form and their colour. Ferber's Travels in
Italy, p. 42.
6. NODULES OF FLINT IN CHALK-BEDS.
As the nodules of flint found in chalk-beds possess no marks of having
been rounded by attrition or solution, I conclude that they have gained
their form as well as their dark colour from the flesh of the shell-fish
from which they had their origin; but which have been so compleatly
fused by heat, or heat and water, as to obliterate all vestiges of the
shell, in the same manner as the nodules of agate and onyx were produced
from parts of vegetables, but which had been so completely fused as to
obliterate all marks of their organization, or as many iron-nodules have
obtained their form and origin from peculiar vegetables.
Some nodules in chalk-beds consist of shells of echini filled up with
chalk, the animal having been dissolved away by putrescence in water, or
eaten by other sea-insects; other shells of echini, in which I suppose
the animal's body remained, are converted into flint but still retain
the form of the shell. Others, I suppose as above, being more completely
fused, have become flint coloured by the animal flesh, but without the
exact form either of the flesh or shell of the animal. Many of these are
hollow within and lined with crystals, like the Scot's-pebbles above
described; but as the colouring matter of animal bodies differs but
little from each other compared with those of vegetables, these flints
vary less in their colours than those above mentioned. At the same time
as they cooled in concentric spheres like the Scot's-pebbles, they often
possess faint rings of colours, and always break in conchoide forms
like them.
This idea of the production of nodules of flint in chalk-beds is
countenanced from the iron which generally appears as these flints
become decomposed by the air; which by uniting with the iron in their
composition reduces it from a vitrescent state to that of calx, and thus
renders it visible. And secondly, by there being no appearance in chalk-
beds of a string or pipe of siliceous matter connecting one nodule with
another, which must have happened if the siliceous matter, or its acid,
had been injected from without according to the idea of Dr. Hutton. And
thirdly, because many of them have very large cavities at their centres,
which should not have happened had they been formed by the injection of
a material from without.
When shells or chalk are thus converted from calcareous to siliceous
matter by the flesh of the animal, the new flint being heavier than the
shell or chalk occupies less space than the materials it was produced
from; this is the cause of frequent cavities within them, where the
whole mass has not been completely fused and pressed together. In
Derbyshire there are masses of coralloid and other shells which have
become siliceous, and are thus left with large vacuities sometimes
within and sometimes on the outside of the remaining form of the shell,
like the French millstones, and I suppose might serve the same purpose;
the gravel of the Derwent is full of specimens of this kind.
Since writing the above I have received a very ingenious account of
chalk-beds from Dr. MENISH of Chelmsford. He distinguishes chalk-beds
into three kinds; such as have been raised from the sea with little
disturbance of their strata, as the cliffs of Dover and Margate, which
he terms _intire_ chalk. Another state of chalk is where it has suffered
much derangement, as the banks of the Thames at Gravesend and Dartford.
And a third state where fragments of chalk have been rounded by water,
which he terms _alluvial_ chalk. In the first of these situations of
chalk he observes, that the flint lies in strata horizontally, generally
in distinct nodules, but that he has observed two instances of solid
plates or strata of flint, from an inch to two inches in thickness,
interposed between the chalk-beds; one of these is in a chalk-bank by
the road side at Berkhamstead, the other in a bank on the road from
Chatham leading to Canterbury. Dr. Menish has further observed, that
many of the echini are crushed in their form, and yet filled with flint,
which has taken the form of the crushed shell, and that though many
flint nodules are hollow, yet that in some echini the siliceum seems to
have enlarged, as it passed from a fluid to a solid state, as it swells
out in a protuberance at the mouth and anus of the shell, and that
though these shells are so filled with flint yet that in many places the
shell itself remains calcareous. These strata of nodules and plates of
flint seem to countenance their origin from the flesh of a stratum of
animals which perished by some natural violence, and were buried in
their shells.
7. ANGLES OF SILICEOUS SAND.
In many rocks of siliceous sand the particles retain their angular form,
and in some beds of loose sand, of which there is one of considerable
purity a few yards beneath the marl at Normington about a mile south of
Derby. Other siliceous sands have had their angles rounded off, like the
pebbles in gravel-beds. These seem to owe their globular form to two
causes; one to their attrition against each other, when they may for
centuries have lain at the bottom of the sea, or of rivers; where they
may have been progressively accumulated, and thus progressively at the
same time rubbed upon each other by the dashing of the water, and where
they would be more easily rolled over each other by their gravity being
so much less than in air. This is evidently now going on in the river
Derwent, for though there are no limestone rocks for ten or fifteen
miles above Derby, yet a great part of the river-gravel at Derby
consists of limestone nodules, whose angles are quite worn off in their
descent down the stream.
There is however another cause which must have contributed to round the
angles both of calcareous and siliceous fragments; and that is, their
solubility in water; calcareous earth is perpetually found suspended in
the waters which pass over it; and the earth of flints was observed by
Bergman to be contained in water in the proportion of one grain to a
gallon. Kirwan's Mineralogy, p. 107. In boiling water, however, it is
soluble in much greater proportion, as appears from the siliceous earth
sublimed in the distillation of fluor acid in glass vessels; and from
the basons of calcedony which surrounded the jets of hot water near
mount Heccla in Iceland. Troil on Iceland. It is probable most siliceous
sands or pebbles have at some ages of the world been long exposed to
aqueous steams raised by subterranean fires. And if fragments of stone
were long immersed in a fluid menstrum, their angular parts would be
first dissolved, on account of their greater surface.
Many beds of siliceous gravel are cemented together by a siliceous
cement, and are called breccia; as the plumb-pudding stones of
Hartfordshire, and the walls of a subterraneous temple excavated by Mr.
Curzon, at Hagley near Rugely in Staffordfshire; these may have been
exposed to great heat as they were immersed in water; which water under
great pressure of superincumbent materials may have been rendered red-
hot, as in Papin's digester; and have thus possessed powers of solution
with which we are unacquainted.
8. BASALTES AND GRANITES.
Another source of siliceous stones is from the granite, or basaltes, or
porphyries, which are of different hardnesses according to the materials
of their composition, or to the fire they have undergone; such are the
stones of Arthur's-hill near Edinburgh, of the Giant's Causway in
Ireland, and of Charnwood Forest in Leicestershire; the uppermost
stratum of which last seems to have been cracked either by its
elevation, or by its hastily cooling after ignition by the contact of
dews or snows, and thus breaks into angular fragments, such as the
streets of London are paved with; or have had their angles rounded by
attrition or by partial solution; and have thus formed the common paving
stones or bowlers; as well as the gravel, which is often rolled into
strata amid the siliceous sand-beds, which are either formed or
collected in the sea.
In what manner such a mass of crystallized matter as the Giant's Causway
and similar columns of basaltes, could have been raised without other
volcanic appearances, may be a matter not easy to comprehend; but there
is another power in nature besides that of expansile vapour which may
have raised some materials which have previously been in igneous or
aqueous solution; and that is the act of congelation. When the water in
the experiments above related of Major Williams had by congelation
thrown out the plugs from the bomb-shells, a column of ice rose from the
hole of the bomb six or eight inches high. Other bodies I suspect
increase in bulk which crystallize in cooling, as iron and type-metal. I
remember pouring eight or ten pounds of melted brimstone into a pot to
cool and was surprized to see after a little time a part of the fluid
beneath break a hole in the congealed crust above it, and gradually rise
into a promontory several inches high; the basaltes has many marks of
fusion and of crystallization and may thence, as well as many other
kinds of rocks, as of spar, marble, petrosilex, jasper, &c. have been
raised by the power of congelation, a power whose quantity has not yet
been ascertained, and perhaps greater and more universal than that of
vapours expanded by heat. These basaltic columns rise sometimes out of
mountains of granite itself, as mentioned by Dr. Beddoes, (Phil.
Transact. Vol. LXXX.) and as they seem to consist of similar materials
more completely fused, there is still greater reason to believe them to
have been elevated in the cooling or crystallization of the mass. See
note XXIV.
NOTE XX.--CLAY.
_Whence ductile Clays in wide expansion spread,
Soft as the Cygnet's down, their snow-white bed._
CANTO II. l. 277.
The philosophers, who have attended to the formation of the earth, have
acknowledged two great agents in producing the various changes which the
terraqueous globe has undergone, and these are water and fire. Some of
them have perhaps ascribed too much to one of these great agents of
nature, and some to the other. They have generally agreed that the
stratification of materials could only be produced from sediments or
precipitations, which were previously mixed or dissolved in the sea; and
that whatever effects were produced by fire were performed afterwards.
There is however great difficulty in accounting for the universal
stratification of the solid globe of the earth in this manner, since
many of the materials, which appear in strata, could not have been
suspended in water; as the nodules of flint in chalk-beds, the extensive
beds of shells, and lastly the strata of coal, clay, sand, and iron-ore,
which in most coal-countries lie from five to seven times alternately
stratified over each other, and none of them are soluble in water. Add
to this if a solution of them or a mixture of them in water could be
supposed, the cause of that solution must cease before a precipitation
could commence.
1. The great masses of lava, under the various names of granite,
porphyry, toadstone, moor-stone, rag, and slate, which constitute the
old world, may have acquired the stratification, which some of them
appear to possess, by their having been formed by successive eruptions
of a fluid mass, which at different periods of antient time arose from
volcanic shafts and covered each other, the surface of the interior mass
of lava would cool and become solid before the superincumbent stratum
was poured over it; to the same cause may be ascribed their different
compositions and textures, which are scarcely the same in any two parts
of the world.
2. The stratifications of the great masses of limestone, which were
produced from sea-shells, seem to have been formed by the different
times at which the innumerable shells were produced and deposited. A
colony of echini, or madrepores, or cornua ammonis, lived and perished
in one period of time; in another a new colony of either similar or
different shells lived and died over the former ones, producing a
stratum of more recent shell over a stratum of others which had began to
petrify or to become marble; and thus from unknown depths to what are
now the summits of mountains the limestone is disposed in strata of
varying solidity and colour. These have afterwards undergone variety of
changes by their solution and deposition from the water in which they
were immersed, or from having been exposed to great heat under great
pressure, according to the ingenious theory of Dr. Hutton. Edinb.
Transact. Vol. I. See Note XVI.
3. In most of the coal-countries of this island there are from five to
seven beds of coal stratified with an equal number of beds, though of
much greater thickness, of clay and sandstone, and occasionally of iron-
ores. In what manner to account for the stratification of these
materials seems to be a problem of greater difficulty. Philosophers have
generally supposed that they have been arranged by the currents of the
sea; but considering their insolubility in water, and their almost
similar specific gravity, an accumulation of them in such distinct beds
from this cause is altogether inconceiveable, though some coal-countries
bear marks of having been at some time immersed beneath the waves and
raised again by subterranean fires.
The higher and lower parts of morasses were necessarily produced at
different periods of time, see Note XVII. and would thus originally be
formed in strata of different ages. For when an old wood perished, and
produced a morass, many centuries would elapse before another wood could
grow and perish again upon the same ground, which would thus produce a
new stratum of morass over the other, differing indeed principally in
its age, and perhaps, as the timber might be different, in the
proportions of its component parts.
Now if we suppose the lowermost stratum of a morass become ignited, like
fermenting hay, (after whatever could be carried away by solution in
water was gone,) what would happen? Certainly the inflammable part, the
oil, sulphur, or bitumen, would burn away, and be evaporated in air; and
the fixed parts would be left, as clay, lime, and iron; while some of
the calcareous earth would join with the siliceous acid, and produce
sand, or with the argillaceous earth, and produce marl. Thence after
many centuries another bed would take fire, but with less degree of
ignition, and with a greater body of morass over it, what then would
happen? The bitumen and sulphur would rise and might become condensed
under an impervious stratum, which might not be ignited, and there form
coal of different purities according to its degree of fluidity, which
would permit some of the clay to subside through it into the place from
which it was sublimed.
Some centuries afterwards another similar process might take place, and
either thicken the coal-bed, or produce a new clay-bed, or marl, or
sand, or deposit iron upon it, according to the concomitant
circumstances above mentioned.
I do not mean to contend that a few masses of some materials may not
have been rolled together by currents, when the mountains were much more
elevated than at present, and in consequence the rivers broader and more
rapid, and the storms of rain and wind greater both in quantity and
force. Some gravel-beds may have been thus washed from the mountains;
and some white clay washed from morasses into valleys beneath them; and
some ochres of iron dissolved and again deposited by water; and some
calcareous depositions from water, (as the bank for instance on which
stand the houses at Matlock-bath;) but these are of small extent or
consequence compared to the primitive rocks of granite or porpyhry which
form the nucleus of the earth, or to the immense strata of limestone
which crust over the greatest part of this granite or porphyry; or
lastly to the very extensive beds of clay, marl, sandstone, coal, and
iron, which were probably for many millions of years the only parts of
our continents and islands, which were then elevated above the level of
the sea, and which on that account became covered with vegetation, and
thence acquired their later or superincumbent strata, which constitute,
what some have termed, the new world.
There is another source of clay, and that of the finest kind, from
decomposed granite, this is of a snowy white and mixed with mining
particles of mica, of this kind is an earth from the country of
Cherokees. Other kinds are from less pure lavas; Mr. Ferber asserts that
the sulphurous steams from Mount Vesuvius convert the lava into clay.
"The lavas of the antient Solfatara volcano have been undoubtedly of a
vitreous nature, and these appear at present argillaceous. Some
fragments of this lava are but half or at one side changed into clay,
which either is viscid or ductile, or hard and stoney. Clays by fire are
deprived of their coherent quality, which cannot be restored to them by
pulverization, nor by humectation. But the sulphureous Solfatara steams
restore it, as may be easily observed on the broken pots wherein they
gather the sal ammoniac; though very well baked and burnt at Naples they
are mollified again by the acid steams into a viscid clay which keeps
the former fire-burnt colour." Travels in Italy, p. 156.
NOTE XXI.--ENAMELS.
_Smear'd her huge dragons with metallic hues,
With golden purples, and cobaltic blues;_
CANTO II. l. 287.
The fine bright purples or rose colours which we see on china cups are
not producible with any other material except gold, manganese indeed
gives a purple but of a very different kind.
In Europe the application of gold to these purposes appears to be of
modern invention. Cassius's discovery of the precipitate of gold by tin,
and the use of that precipitate for colouring glass and enamels, are now
generally known, but though the precipitate with tin be more successful
in producing the ruby glass, or the colourless glass which becomes red
by subsequent ignition, the tin probably contributing to prevent the
gold from separating, (which it is very liable to do during the fusion;
yet, for enamels, the precipitates made by alcaline salts answer equally
well, and give a finer red, the colour produced by the tin precipitate
being a bluish purple, but with the others a rose red. I am informed
that some of our best artists prefer aurum fulminans, mixing it, before
it has become dry, with the white composition or enamel flux; when once
it is divided by the other matter, it is ground with great safety, and
without the least danger of explosion, whether moist or dry. The colour
is remarkably improved and brought forth by long grinding, which
accordingly makes an essential circumstance in the process.
The precipitates of gold, and the colcothar or other red preparations of
iron, are called _tender_ colours. The heat must be no greater than is
just sufficient to make the enamel run upon the piece, for if greater,
the colours will be destroyed or changed to a different kind. When the
vitreous matter has just become fluid it seems as if the coloured
metallic calx remained barely _intermixed_ with it, like a coloured
powder of exquisite tenuity suspended in water: but by stronger fire the
calx is _dissolved_, and metallic colours are altered by _solution_ in
glass as well as in acids or alcalies.
The Saxon mines have till very lately almost exclusively supplied the
rest of Europe with cobalt, or rather with its preparations, zaffre and
smalt, for the exportation of the ore itself is there a capital crime.
Hungary, Spain, Sweden, and some other parts of the continent, are now
said to afford cobalts equal to the Saxon, and specimens have been
discovered in our own island, both in Cornwall and in Scotland; but
hitherto in no great quantity.
Calces of cobalt and of copper differ very materially from those above
mentioned in their application for colouring enamels. In those the calx
has previously acquired the intended colour, a colour which bears a red
heat without injury, and all that remains is to fix it on the piece by a
vitreous flux. But the blue colour of cobalt, and the green or bluish
green of copper, are _produced_ by vitrification, that is, by _solution_
in the glass, and a strong fire is necessary for their perfection. These
calces therefore, when mixed with the enamel flux, are melted in
crucibles, once or oftener, and the deep coloured opake glass, thence
resulting, is ground into unpalpable powder, and used for enamel. One
part of either of these calces is put to ten, sixteen, or twenty parts
of the flux, according to the depth of colour required. The heat of the
enamel kiln is only a full red, such as is marked on Mr. Wedgwood's
thermometer 6 degrees. It is therefore necessary that the flux be so
adjusted as to melt in that low heat. The usual materials are flint, or
flint-glass, with a due proportion of red-led, or borax, or both, and
sometimes a little tin calx to give opacity.
_Ka-o-lin_ is the name given by the Chinese to their porcelain clay, and
_pe-tun-tse_ to the other ingredient in their China ware. Specimens of
both these have been brought into England, and found to agree in quality
with some of our own materials. Kaolin is the very same with the clay
called in Cornwall [Transcriber's note: word missing] and the petuntse
is a granite similar to the Cornish moorstone. There are differences,
both in the Chinese petuntses, and the English moorstones; all of them
contain micaceous and quartzy particles, in greater or less quantity,
along with feltspat, which last is the essential ingredient for the
porcelain manufactory. The only injurious material commonly found in
them is iron, which discolours the ware in proportion to its quantity,
and which our moorstones are perhaps more frequently tainted with than
the Chinese. Very fine porcelain has been made from English materials
but the nature of the manufacture renders the process precarious and the
profit hazardous; for the semivitrification, which constitutes
porcelain, is necessarily accompanied with a degree of softness, or
semifusion, so that the vessels are liable to have their forms altered
in the kiln, or to run together with any accidental augmentations of the
fire.
NOTE XXII.--PORTLAND VASE.
_Or bid Mortality rejoice or mourn
O'er the fine forms of Portland's mystic urn._
CANTO II. l. 319.
The celebrated funereal vase, long in possession of the Barberini
family, and lately purchased by the Duke of Portland for a thousand
guineas, is about ten inches high and six in diameter in the broadest
part. The figures are of most exquisite workmanship in bas relief of
white opake glass, raised on a ground of deep blue glass, which appears
black except when held against the light. Mr. Wedgwood is of opinion
from many circumstances that the figures have been made by cutting away
the external crust of white opake glass, in the manner the finest
cameo's have been produced, and that it must thence have been the labour
of a great many years. Some antiquarians have placed the time of its
production many centuries before the christian aera; as sculpture was
said to have been declining in respect to its excellence in the time of
Alexander the Great. See an account of the Barberini or Portland vase by
M. D'Hancarville, and by Mr. Wedgwood.
Many opinions and conjectures have been published concerning the figures
on this celebrated vase. Having carefully examined one of Mr. Wedgwood's
beautiful copies of this wonderful production of art, I shall add one
more conjecture to the number.
Mr. Wedgwood has well observed that it does not seem probable that the
Portland vase was purposely made for the ashes of any particular person
deceased, because many years must have been necessary for its
production. Hence it may be concluded, that the subject of its
embellishments is not private history but of a general nature. This
subject appears to me to be well chosen, and the story to be finely
told; and that it represents what in antient times engaged the attention
of philosophers, poets, and heroes, I mean a part of the Eleusinian
mysteries.
These mysteries were invented in Aegypt, and afterwards transferred to
Greece, and flourished more particularly at Athens, which was at the
same time the seat of the fine arts. They consisted of scenical
exhibitions representing and inculcating the expectation of a future
life after death, and on this account were encouraged by the government,
insomuch that the Athenian laws punished a discovery of their secrets
with death. Dr. Warburton has with great learning and ingenuity shewn
that the descent of Aeneas into hell, described in the Sixth Book of
Virgil, is a poetical account of the representations of the future state
in the Eleusinian mysteries. Divine Legation, Vol. I. p. 210.
And though some writers have differed in opinion from Dr. Warburton on
this subject, because Virgil has introduced some of his own heroes into
the Elysian fields, as Deiphobus, Palinurus, and Dido, in the same
manner as Homer had done before him, yet it is agreed that the received
notions about a future state were exhibited in these mysteries, and as
these poets described those received notions, they may be said, as far
as these religious doctrines were concerned, to have described the
mysteries.
Now as these were emblematic exhibitions they must have been as well
adapted to the purposes of sculpture as of poetry, which indeed does not
seem to have been uncommon, since one compartment of figures in the
sheild of Aeneas represented the regions of Tartarus. Aen. Lib. X. The
procession of torches, which according to M. De St. Croix was exhibited
in these mysteries, is still to be seen in basso relievo, discovered by
Spon and Wheler. Memoires sur le Mysteres par De St. Croix. 1784. And it
is very probable that the beautiful gem representing the marriage of
Cupid and Psyche, as described by Apuleus, was originally descriptive of
another part of the exhibitions in these mysteries, though afterwards it
became a common subject of antient art. See Divine Legat. Vol. I. p.
323. What subject could have been imagined so sublime for the ornaments
of a funereal urn as the mortality of all things and their
resuscitation? Where could the designer be supplied with emblems for
this purpose, before the Christian era, but from the Eleusinian
mysteries?
1. The exhibitions of the mysteries were of two kinds, those which the
people were permitted to see, and those which were only shewn to the
initiated. Concerning the latter, Aristides calls them "the most
shocking and most ravishing representations." And Stoboeus asserts that
the initiation into the grand mysteries exactly resembles death. Divine
Legat. Vol. I. p. 280, and p. 272. And Virgil in his entrance to the
shades below, amongst other things of terrible form, mentions death.
Aen. VI. This part of the exhibition seems to be represented in one of
the compartments of the Portland vase.
Three figures of exquisite workmanship are placed by the side of a
ruined column whose capital is fallen off, and lies at their feet with
other disjointed stones, they sit on loose piles of stone beneath a
tree, which has not the leaves of any evergreen of this climate, but may
be supposed to be an elm, which Virgil places near the entrance of the
infernal regions, and adds, that a dream was believed to dwell under
every leaf of it. Aen. VI. l. 281. In the midst of this group reclines a
female figure in a dying attitude, in which extreme languor is
beautifully represented, in her hand is an inverted torch, an antient
emblem of extinguished life, the elbow of the same arm resting on a
stone supports her as she sinks, while the other hand is raised and
thrown over her drooping head, in some measure sustaining it and gives
with great art the idea of fainting lassitude. On the right of her sits
a man, and on the left a woman, both supporting themselves on their
arms, as people are liable to do when they are thinking intensely. They
have their backs towards the dying figure, yet with their faces turned
towards her, as if seriously contemplating her situation, but without
stretching out their hands to assist her.
This central figure then appears to me to be an hieroglyphic or
Eleusinian emblem of MORTAL LIFE, that is, the lethum, or death,
mentioned by Virgil amongst the terrible things exhibited at the
beginning of the mysteries. The inverted torch shews the figure to be
emblematic, if it had been designed to represent a real person in the
act of dying there had been no necessity for the expiring torch, as the
dying figure alone would have been sufficiently intelligible;--it would
have been as absurd as to have put an inverted torch into the hand of a
real person at the time of his expiring. Besides if this figure had
represented a real dying person would not the other figures, or one of
them at least, have stretched out a hand to support her, to have eased
her fall among loose stones, or to have smoothed her pillow? These
circumstances evince that the figure is an emblem, and therefore could
not be a representation of the private history of any particular family
or event.
The man and woman on each side of the dying figure must be considered as
emblems, both from their similarity of situation and dress to the middle
figure, and their being grouped along with it. These I think are
hieroglyphic or Eleusinian emblems of HUMANKIND, with their backs toward
the dying figure of MORTAL LIFE, unwilling to associate with her, yet
turning back their serious and attentive countenances, curious indeed to
behold, yet sorry to contemplate their latter end. These figures bring
strongly to one's mind the Adam and Eve of sacred writ, whom some have
supposed to have been allegorical or hieroglyphic persons of Aegyptian
origin, but of more antient date, amongst whom I think is Dr. Warburton.
According to this opinion Adam and Eve were the names of two
hieroglyphic figures representing the early state of mankind; Abel was
the name of an hieroglyphic figure representing the age of pasturage,
and Cain the name of another hieroglyphic symbol representing the age of
agriculture, at which time the uses of iron were discovered. And as the
people who cultivated the earth and built houses would increase in
numbers much faster by their greater production of food, they would
readily conquer or destroy the people who were sustained by pasturage,
which was typified by Cain slaying Abel.
2. On the other compartment of this celebrated vase is exhibited an
emblem of immortality, the representation of which was well known to
constitute a very principal part of the shews at the Eleusinian
mysteries, as Dr. Warburton has proved by variety of authority. The
habitation of spirits or ghosts after death was supposed by the antients
to be placed beneath the earth, where Pluto reigned, and dispensed
rewards or punishments. Hence the first figure in this group is of the
MANES or GHOST, who having passed through an open portal is descending
into a dusky region, pointing his toe with timid and unsteady step,
feeling as it were his way in the gloom. This portal Aeneas enters,
which is described by Virgil,--patet atri janua ditis, Aen. VI. l. 126;
as well as the easy descent,--facilis descensus Averni. Ib. The darkness
at the entrance to the shades is humorously described by Lucian. Div.
Legat. Vol. I. p. 241. And the horror of the gates of hell was in the
time of Homer become a proverb; Achilles says to Ulysses, "I hate a liar
worse than the gates of hell;" the same expression is used in Isaiah,
ch. xxxviii. v. 10. The MANES or GHOST appears lingering and fearful,
and wishes to drag after him a part of his mortal garment, which however
adheres to the side of the portal through which he has passed. The
beauty of this allegory would have been expressed by Mr. Pope, by "We
feel the ruling passion strong in death."
A little lower down in the group the manes or ghost is received by a
beautiful female, a symbol of IMMORTAL LIFE. This is evinced by her
fondling between her knees a large and playful serpent, which from its
annually renewing its external skin has from great antiquity, even as
early as the fable of Prometheus, been esteemed an emblem of renovated
youth. The story of the serpent acquiring immortal life from the ass of
Prometheus, who carried it on his back, is told in Bacon's Works, Vol.
V. p. 462. Quarto edit. Lond. 1778. For a similar purpose a serpent was
wrapped round the large hieroglyphic egg in the temple of Dioscuri, as
an emblem of the renewal of life from a state of death. Bryant's
Mythology, Vol II. p. 359. sec. edit. On this account also the serpent
was an attendant on Aesculapius, which seems to have been the name of
the hieroglyphic figure of medicine. This serpent shews this figure to
be an emblem, as the torch shewed the central figure of the other
compartment to be an emblem, hence they agreeably correspond, and
explain each other, one representing MORTAL LIFE, and the other IMMORTAL
LIFE.
This emblematic figure of immortal life sits down with her feet towards
the figure of Pluto, but, turning back her face towards the timid ghost,
she stretches forth her hand, and taking hold of his elbow, supports his
tottering steps, as well as encourages him to advance, both which
circumstances are thus with wonderful ingenuity brought to the eye. At
the same time the spirit loosely lays his hand upon her arm, as one
walking in the dark would naturally do for the greater certainty of
following his conductress, while the general part of the symbol of
IMMORTAL LIFE, being turned toward the figure of Pluto, shews that she
is leading the phantom to his realms.
In the Pamphili gardens at Rome, Perseus in assisting Andromeda to
descend from the rock takes hold of her elbow to steady or support her
step, and she lays her hand loosely on his arm as in this figure. Admir.
Roman. Antiq.
The figure of PLUTO can not be mistaken, as is agreed by most of the
writers who have mentioned this vase; his grisley beard, and his having
one foot buried in the earth, denotes the infernal monarch. He is placed
at the lowest part of the group, and resting his chin on his hand, and
his arm upon his knee, receives the stranger-spirit with inquisitive
attention; it was before observed that when people think attentively
they naturally rest their bodies in some easy attitude, that more animal
power may be employed on the thinking faculty. In this group of figures
there is great art shewn in giving an idea of a descending plain, viz.
from earth to Elysium, and yet all the figures are in reality on an
horizontal one. This wonderful deception is produced first by the
descending step of the manes or ghost; secondly, by the arm of the
sitting figure of immortal life being raised up to receive him as he
descends; and lastly, by Pluto having one foot sunk into the earth.
There is yet another figure which is concerned in conducing the manes or
ghost to the realms of Pluto, and this is LOVE. He precedes the
descending spirit on expanded wings, lights him with his torch, and
turning back his beautiful countenance beckons him to advance. The
antient God of love was of much higher dignity than the modern Cupid. He
was the first that came out of the great egg of night, (Hesiod. Theog.
V. CXX. Bryant's Mythol. Vol. II. p. 348.) and is said to possess the
keys of the sky, sea, and earth. As he therefore led the way into this
life, he seems to constitute proper emblem for leading the way to a
future life. See Bacon's works. Vol. I. p. 568. and Vol. III. p. 582.
Quarto edit.
The introduction of love into this part of the mysteries requires a
little further explanation. The Psyche of the Aegyptians was one of
their most favourite emblems, and represented the soul, or a future
life; it was originally no other than the aurelia, or butterfly, but in
after times was represented by a lovely female child with the beautiful
wings of that insect. The aurelia, after its first stage as an eruca or
caterpillar, lies for a season in a manner dead, and is inclosed in a
sort of coffin, in this state of darkness it remains all the winter, but
at the return of spring it bursts its bonds and comes out with new life,
and in the most beautiful attire. The Aegyptians thought this a very
proper picture of the soul of man, and of the immortality to which it
aspired. But as this was all owing to divine Love, of which EROS was an
emblem, we find this person frequently introduced as a concomitant of
the soul in general or Psyche. (Bryant's Mythol. Vol. II. p. 386.) EROS,
or divine Love, is for the same reason a proper attendant on the manes
or soul after death, and much contributes to tell the story, that is, to
shew that a soul or manes is designed by the descending figure. From
this figure of Love M. D'Hancarville imagines that Orpheus and Eurydice
are typified under the figure of the manes and immortal life as above
described. It may be sufficient to answer, first, that Orpheus is always
represented with a lyre, of which there are prints of four different
gems in Spence's Polymetis, and Virgil so describes him, Aen. VI.
cytharâ fretus. And secondly, that it is absurd to suppose that Eurydice
was fondling and playing with a serpent that had slain her. Add to this
that Love seems to have been an inhabitant of the infernal regions, as
exhibited in the mysteries, for Claudian, who treats more openly of the
Eleusinian mysteries, when they were held in less veneration, invokes
the deities to disclose to him their secrets, and amongst other things
by what torch Love softens Pluto.
Dii, quibus in numerum, &c.
Vos mihi sacrarum penetralia pandite rerum,
Et vestri secreta poli, quâ lampade Ditem
Flexit amor.
In this compartment there are two trees, whose branches spread over the
figures, one of them has smoother leaves like some evergreens, and might
thence be supposed to have some allusion to immortality, but they may
perhaps have been designed only as ornaments, or to relieve the figures,
or because it was in groves, where these mysteries were originally
celebrated. Thus Homer speaks of the woods of Proserpine, and mentions
many trees in Tartarus, as presenting their fruits to Tantalus; Virgil
speaks of the pleasant groves of Elysium; and in Spence's Polymetis
there are prints of two antient gems, one of Orpheus charming Cerberus
with his lyre, and the other of Hercules binding him in a cord, each of
them standing by a tree. Polymet. p. 284. As however these trees have
all different foliage so clearly marked by the artist, they may have had
specific meanings in the exhibitions of the mysteries, which have not
reached posterity, of this kind seem to have been the tree of knowledge
of good and evil, and the tree of life, in sacred writ, both which must
have been emblematic or allegorical. The masks, hanging to the handles
of the vase, seem to indicate that there is a concealed meaning in the
figures besides their general appearance. And the priestess at the
bottom, which I come now to describe, seems to shew this concealed
meaning to be of the sacred or Eleusinian kind.
3. The figure on the bottom of the vase is on a larger scale than the
others, and less finely finished, and less elevated, and as this bottom
part was afterwards cemented to the upper part, it might be executed by
another artist for the sake of expedition, but there seems no reason to
suppose that it was not originally designed for the upper part of it as
some have conjectured. As the mysteries of Ceres were celebrated by
female priests, for Porphyrius says the antients called the priestesses
of Ceres, Melissai, or bees, which were emblems of chastity. Div. Leg.
Vol. I. p. 235. And as, in his Satire against the sex, Juvenal says,
that few women are worthy to be priestesses of Ceres. Sat. VI. the
figure at the bottom of the vase would seem to represent a PRIESTESS or
HIEROPHANT, whose office it was to introduce the initiated, and point
out to them, and explain the exhibitions in the mysteries, and to
exclude the uninitiated, calling out to them, "Far, far retire, ye
profane!" and to guard the secrets of the temple. Thus the introductory
hymn sung by the hierophant, according to Eusebius, begins, "I will
declare a secret to the initiated, but let the doors be shut against the
profane." Div. Leg. Vol. I. p. 177. The priestess or hierophant appears
in this figure with a close hood, and dressed in linen, which fits close
about her; except a light cloak, which flutters in the wind. Wool, as
taken from slaughtered animals, was esteemed profane by the priests of
Aegypt, who were always dressed in linen. Apuleus, p. 64. Div. Leg. Vol.
I. p. 318. Thus Eli made for Samuel a linen ephod. Samuel i. 3.
Secrecy was the foundation on which all mysteries rested, when publicly
known they ceased to be mysteries; hence a discovery of them was not
only punished with death by the Athenian law; but in other countries a
disgrace attended the breach of a solemn oath. The priestess in the
figure before us has her finger pointing to her lips as an emblem of
silence. There is a figure of Harpocrates, who was of Aegyptian origin,
the same as Orus, with the lotus on his head, and with his finger
pointing to his lips not pressed upon them, in Bryant's Mythol. Vol. II.
p. 398, and another female figure standing on a lotus, as if just risen
from the Nile, with her finger in the same attitude, these seem to have
been representations or emblems of male and female priests of the secret
mysteries. As these sort of emblems were frequently changed by artists
for their more elegant exhibition, it is possible the foliage over the
head of this figure may bear some analogy to the lotus above mentioned.
This figure of secrecy seems to be here placed, with great ingenuity, as
a caution to the initiated, who might understand the meaning of the
emblems round the vase, not to divulge it. And this circumstance seems
to account for there being no written explanation extant, and no
tradition concerning these beautiful figures handed down to us along
with them.
Another explanation of this figure at the bottom of the vase would seem
to confirm the idea that the basso relievos round its sides are
representations of a part of the mysteries, I mean that it is the head
of ATIS. Lucian says that Atis was a young man of Phrygia, of uncommon
beauty, that he dedicated a temple in Syria to Rhea, or Cybele, and
first taught her mysteries to the Lydians, Phrygians, and Samothracians,
which mysteries he brought from India. He was afterwards made an eunuch
by Rhea, and lived like a woman, and assumed a feminine habit, and in
that garb went over the world teaching her ceremonies and mysteries.
Dict. par M. Danet, art. Atis. As this figure is covered with clothes,
while those on the sides of the vase are naked, and has a Phrygian cap
on the head, and as the form and features are so soft, that it is
difficult to say whether it be a male or female figure, there is reason
to conclude, 1. that it has reference to some particular person of some
particular country; 2. that this person is Atis, the first great
hierophant, or teacher of mysteries, to whom M. De la Chausse says the
figure itself bears a resemblance. Museo. Capitol. Tom. IV. p. 402.
In the Museum Etruscum, Vol. I. plate 96, there is the head of Atis with
feminine features, clothed with a Phrygian cap, and rising from very
broad foliage, placed on a kind of term supported by the paw of a lion.
Goreus in his explanation of the figure says that it is placed on a
lion's foot because that animal was sacred to Cybele, and that it rises
from very broad leaves because after he became an eunuch he determined
to dwell in the groves. Thus the foliage, as well as the cap and
feminine features, confirm the idea of this figure at the bottom of the
vase representing the head of Atis the first great hierophant, and that
the figures on the sides of the vase are emblems from the antient
mysteries.
I beg leave to add that it does not appear to have been uncommon amongst
the antients to put allegorical figures on funeral vases. In the
Pamphili palace at Rome there is an elaborate representation of Life and
of Death, on an antient sarcophagus. In the first Prometheus is
represented making man, and Minerva is placing a butterfly, or the soul,
upon his head. In the other compartment Love extinguishes his torch in
the bosom of the dying figure, and is receiving the butterfly, or
Psyche, from him, with a great number of complicated emblematic figures
grouped in very bad taste. Admir. Roman. Antiq.
NOTE XXIII.--COAL
_Whence sable Coal his massy couch extends,
And stars of gold the sparkling Pyrite blends._
CANTO II. l. 349.
To elucidate the formation of coal-beds I shall here describe a fountain
of fossil tar, or petroleum, discovered lately near Colebrook Dale in
Shropshire, the particulars of which were sent me by Dr. Robert Darwin
of Shrewsbury.
About a mile and a half below the celebrated iron-bridge, constructed by
the late Mr. DARBY near Colebrook Dale, on the east side of the river
Severn, as the workmen in October 1786 were making a subterranean canal
into the mountain, for the more easy acquisition and conveyance of the
coals which lie under it, they found an oozing of liquid bitumen, or
petroleum; and as they proceeded further cut through small cavities of
different sizes from which the bitumen issued. From ten to fifteen
barrels of this fossil tar, each barrel containing thirty-two gallons,
were at first collected in a day, which has since however gradually
diminished in quantity, so that at present the product is about seven
barrels in fourteen days.
The mountain, into which this canal enters, consists of siliceous sand,
in which however a few marine productions, apparently in their recent
state, have been found, and are now in the possession of Mr. WILLIAM
REYNOLDS of Ketly Bank. About three hundred yards from the entrance into
the mountain, and about twenty-eight yards below the surface of it, the
tar is found oozing from the sand-rock above into the top and sides of
the canal.
Beneath the level of this canal a shaft has been sunk through a grey
argillaceous substance, called in this country clunch, which is said to
be a pretty certain indication of coal; beneath this lies a stratum of
coal, about two or three inches thick, of an inferior kind, yielding
little flame in burning, and leaving much ashes; below this is a rock of
a harder texture; and beneath this are found coals of an excellent
quality; for the purpose of procuring which with greater facility the
canal, or horizontal aperture, is now making into the mountain. July,
1788.
Beneath these coals in some places is found salt water, in other parts
of the adjacent country there are beds of iron-stone, which also contain
some bitumen in a less fluid state, and which are about on a level with
the new canal, into which the fossil tar oozes, as above described.
There are many interesting circumstances attending the situation and
accompaniments of this fountain of fossil tar, tending to develop the
manner of its production. 1. As the canal passing into the mountain runs
over the beds of coals, and under the reservoir of petroleum, it appears
that a _natural distillation_ of this fossil in the bowels of the earth
must have taken place at some early period of the world, similar to the
artificial distillation of coal, which has many years been carried on in
this place on a smaller scale above ground. When this reservoir of
petroleum was cut into, the slowness of its exsudation into the canal
was not only owing to its viscidity, but to the pressure of the
atmosphere, or to the necessity there was that air should at the same
time insinuate itself into the small cavities from which the petroleum
descended. The existence of such a distillation at some antient time is
confirmed by the thin stratum of coal beneath the canal, (which covers
the hard rock,) having been deprived of its fossil oil, so as to burn
without flame, and thus to have become a natural coak, or fossil
charcoal, while the petroleum distilled from it is found in the cavities
of the rock above it.
There are appearances in other places, which favour this idea of the
natural distillation of petroleum, thus at Matlock in Derbyshire a hard
bitumen is found adhering to the spar in the clefts of the lime-rocks in
the form of round drops about the size of peas; which could perhaps only
be deposited there in that form by sublimation.
2. The second deduction, which offers itself, is, that these beds of
coal have been _exposed to a considerable degree of heat_, since the
petroleum above could not be separated, as far as we know, by any other
means, and that the good quality of the coals beneath the hard rock was
owing to the impermeability of this rock to the bituminous vapour, and
to its pressure being too great to permit its being removed by the
elasticity of that vapour. Thus from the degree of heat, the degree of
pressure, and the permeability of the superincumbent strata, many of the
phenomena attending coal-beds receive an easy explanation, which much
accords with the ingenious theory of the earth by Dr. Hutton, Trans. of
Edinb. Vol. I.
In some coal works the fusion of the strata of coal has been so slight,
that there remains the appearance of ligneus fibres, and the impression
of leaves, as at Bovey near Exeter, and even seeds of vegetables, of
which I have had specimens from the collieries near Polesworth in
Warwickshire. In some, where the heat was not very intense and the
incumbent stratum not permeable to vapour, the fossil oil has only risen
to the upper part of the coal-bed, and has rendered that much more
inflammable than the lower parts of it, as in the collieries near
Beaudesert, the seat of the EARL OF UXBRIDGE in Staffordshire, where the
upper stratum is a perfect cannel, or candle-coal, and the lower one of
an inferior quality. Over the coal-beds near Sir H. HARPUR'S house in
Derbyshire a thin lamina of asphaltum is found in some places near the
surface of the earth, which would seem to be from a distillation of
petroleum from the coals below, the more fluid part of which had in
process of time exhaled, or been consolidated by its absorption of air.
In other coal-works the upper part of the stratum is of a worse kind
than the lower one, as at Alfreton and Denbigh in Derbyshire, owing to
the supercumbent stratum having permitted the exhalation of a great part
of the petroleum; whilst at Widdrington in Northumberland there is first
a seam of coal about six inches thick of no value, which lies under
about four fathom of clay, beneath this is a white freestone, then a
hard stone, which the workmen there call a whin, then two fathoms of
clay, then another white stone, and under that a vein of coals three
feet nine inches thick, of a similar nature to the Newcastle coal. Phil.
Trans. Abridg. Vol. VI. plate II. p. 192. The similitude between the
circumstances of this colliery, and of the coal beneath the fountain of
tar above described, renders it highly probable that this upper thin
seam of coal has suffered a similar distillation, and that the
inflammable part of it had either been received into the clay above in
the form of sulphur, which when burnt in the open air would produce
alum; or had been dissipated for want of a receiver, where it could be
condensed. The former opinion is perhaps in this case more probable as
in some other coal-beds, of which I have procured accounts, the surface
of the coal beneath clunch or clay is of an inferior quality, as at West
Hallum in Nottinghamshire. The clunch probably from hence acquires its
inflammable part, which on calcination becomes vitriolic acid. I
gathered pieces of clunch converted partially into alum at a colliery
near Bilston, where the ground was still on fire a few years ago.
The heat, which has thus pervaded the beds of morass, seems to have been
the effect of the fermentation of their vegetable materials; as new hay
sometimes takes fire even in such very small masses from the sugar it
contains, and seems hence not to have been attended with any expulsion
of lava, like the deeper craters of volcanos situated in beds of
granite.
3. The marine shells found in the loose sand-rock above this reservoir
of petroleum, and the coal-beds beneath it, together with the existence
of sea-salt beneath these coals, prove that these coal beds have been
_at the bottom of the sea_, during some remote period of time, and were
afterwards raised into their present situation by subterraneous
expansions of vapour. This doctrine is further supported by the marks of
violence, which some coal-beds received at the time they were raised out
of the sea, as in the collieries at Mendip in Somersetshire. In these
there are seven strata of coals, equitant upon each other, with beds of
clay and stone intervening; amongst which clay are found shells and fern
branches. In one part of this hill the strata are disjoined, and a
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