Scientific American Supplement, No. 447, July 26, 1884
by
Various
Part 2 out of 3
We will now briefly examine, by aid of these methods, the group of rocks
in which coal occurs in Great Britain, and see how far we can read the
story they have to tell.
The group with which we have to deal is called the carboniferous or
coal bearing system, and it includes four classes of rocks, viz.: 1,
sandstone; 2, shale or bind; 3, limestone; 4, coal and underclay.
We will take the sandstones and shales first. They are grains of sand
known to mineralogists as quartz, and consisting of a substance called
silica by chemists. The grains of sand are bound together by a cement
which in some few cases is identical in composition with themselves, and
consists of pure silica, but usually is a mixture of sandy, clayey, and
other substances. The shales are made up very largely of clay, mixed,
however, usually with sand and other substances, forming a conglomerate.
Both sandstones and shales are divided into layers or beds, and are said
to be stratified. It is this stratified or bedded structure that gives
us the first clew to the way in which these rocks were formed. Rivers
are constantly carrying down sand and mud into the sea or lakes, and
when their flow is slackened on entering the still water the materials
they bring down with them sink and are spread out in layers over the
bottom. The structure of the sandstones and shales shows that they were
formed in this way; they often inclose the remains of plants that have
been carried down from land, and occasionally of animals that lived in
the water where they were deposited.
The next we have to consider is limestone, which is mainly made up of a
substance known to chemists as calcium carbonate, or carbonate of lime.
In some districts, especially in volcanic countries, springs occur very
highly charged with carbonate of lime. The warm springs of Matlock are
a case in point; they are probably the last vestige of volcanic action
which was in operation in that neighborhood during carboniferous times.
Limestone is chiefly formed by the agency of small marine creatures of
low organization. By the aid of these animals the carbonate of lime is
brought back to a solid form; at their death their hard parts fall to
the bottom and accumulate in a mass of pure limestone, which afterward
becomes solidified into limestone rock.
The information that limestone gives us is this:
When we find, as is often the case, a mass of limestone hundreds of feet
thick, and composed of little else but carbonate of lime, we know that
the spot where it occurs was, at the time it was formed, far out at sea,
covered by the clear water of mid ocean; and when we find that this
limestone grows in certain directions earthy and impure, and that layers
of shale and sandstone, thin at first, but gradually thickening out in
a wedge-shape form, come in between its beds, we know that in those
directions we are traveling toward the shore lines of that sea whence
the water was receiving from time to time supplies of muddy and sandy
sediment.
The next class of rocks are the clays that are found beneath every
bed of coal, and which are known as _underclays_, or _warrant_, or
_spavins_. They vary very much in mineral composition. Sometimes they
are soft clay; sometimes clay mixed with a certain portion of sand; and
sometimes they contain such a large proportion of silicious matters that
they become hard, flinty rock, which many of you know under the name
of _gannister_. But all underclays agree in two points: they are all
unstratified. They differ totally from the shales and sandstones in this
respect, and instead of splitting up readily into thin flakes, they
break up into irregular lumpy masses. And they all contain a very
peculiar vegetable fossil called _Stigmaria_.
This strange fossil was for a long time a sore puzzle to fossil
botanists, and after much discussion the question was fairly solved by
Mr. Binney by the discovery of a tree embedded in the coal measures,
and standing erect just as it grew, with its roots spread out into the
stratum on which it stood. These roots were Stigmaria, and the stuff
into which they penetrated was an underclay. Sir Charles Lyell mentions
an individual sigillaria 72 feet in length found at Newcastle, and a
specimen taken from the Jarrow coal mine was more than 40 feet in length
and 13 feet in diameter near the base. It is not often these trees are
found erect, because the action of water, combined with natural decay,
has generally thrown them down. They are, however, found in very large
numbers in the roof of the coal, evidently having been tossed over, and
lying there flat and squeezed thin by the pressure of the measures that
lie above them.
Lastly, we come to coal itself--a rock which constitutes a small portion
of the whole bulk of the carboniferous deposits, but which may be fairly
looked upon as the most important member of that group, both on account
of its intrinsic value and also from the interest that attaches to its
history. That coal is little else but mineralized vegetable matter is a
point on which there has for a long time been but small doubt. The
more minute investigations of recent years have not only placed this
completely beyond question, but have also enabled us to say what the
plants were which contributed to the formation of coal, and in some
cases even to decide what portions of those plants enter into its
composition. It is a thing so universally admitted on all hands, that I
shall take it for granted you are all perfectly convinced that coal has
been nothing in the world but a great mass of vegetable matter. The only
question is: How were these great masses of vegetable matter brought
together? And you must realize that they were very large masses indeed.
Just to take one instance. The Yorkshire and Derbyshire coal field is
somewhere about 700 to 800 square miles in area, and Lancashire about
200. Well, in both these coal fields you have a great number of beds of
coal that spread over the whole of them with tolerable regularity and
thickness, and very often with scarcely any break whatever. And this is
only a very small portion of what must have been the original sheet of
coal, so that you see we have to account for a mass of vegetable matter
perfectly free from any admixture of sand, mud, or dirt, and laid down
with tolerably uniform thickness over many hundreds of square miles.
At one time it was supposed that coal was formed out of dead trees and
plants which were swept down by rivers into the sea, just in the same
way as shales and sandstones were formed out of mud and sand so swept
down. The fatal objection to this theory, however, is that rivers would
not bring down dead wood alone, but they would bring down sand and mud,
and other matters, and that in the bottom of the sea the dead wood would
be mixed with these matters, and instead of getting a perfectly unmixed
mass of vegetable matter, we should get a mixture of dead plants, sand,
mud, and other things, which would give rise to something like coal, but
something very different, as any one who tries to burn such coal will
soon find out, from really good, pure house coal. So that this theory,
which is generally known as the "drift" theory, was totally inadequate
to account for the facts as we know them.
The other theory was that coal was formed out of plants and trees that
grew on the spot where we now find coal itself. On this supposition it
is easy to account for the absence of foreign admixtures of sand, mud,
and clay in the coal; and we can also understand very much better than
by the aid of the drift theory how the coal had accumulated with such
wonderful uniformity of thickness over such very large areas. This
theory was for some time but poorly received; but after the discovery
of Sir William Logan, that every bed of coal had a bed of underclay
beneath, and the discovery of Mr. Binney, that these underclays were
true soils on which plants had undoubtedly grown, there was no doubt
whatever that this was the real and true explanation of the matter.
I dare say many of you have had occasion to walk across peat bogs.
The peat bog is a great mass of vegetable matter, which is every year
growing thicker and thicker; and underneath it there is almost always a
bed of thin clay, in look very much like the underclays, and this thin
clay is penetrated by the rootlets of the moss forming the peat, exactly
the same way as the underclays of the coal measures are penetrated by
the stigmaria and its rootlets. But you must not suppose that the plants
out of which coal was formed were exactly the same low type of moss
which forms our present peat bogs. However, it is pretty certain that
they were for the most part of a loose, succulent texture, and that they
grew very rapidly indeed.
You will have noticed that there is one step more wanted to make good
this theory of the growth of coal on the spot where we now find it.
The coal is found, as already described, interbedded with shales and
sandstones. These shales and sandstones, as shown, were formed beneath
the water of the sea, and as long as they remained there of course no
plants could grow upon them. The question is, How was the land surface
formed for the growth of plants? It must have been formed in some way or
other by the sea bottom having been raised above the level of the water.
Now, we have distinct proof in many cases that elevation of the sea
bottom and depression of the land is now going on in many parts of the
earth's surface. And, therefore, we shall be assuming nothing beyond the
range of experience if we say that such elevations and depressions went
on during coal measure times. The coal measure times must have been
times during which the same spot was now below the sea, and now dry
land, over and over again. There was a land surface on which plants grew
fast and multiplied rapidly, and as they died fell and accumulated in
a great heap of dead vegetable matter. After a time this layer of
vegetable matter was slowly and gently let down beneath the waters of
the sea--so slowly that the water flowing over it did not, as a rule,
disturb the loose, pasty mass; and then, by the method I have described
to you, shales and sandstones were deposited on the top of this mass
of dead vegetable matter. By their weight they compressed it, and
by certain chemical changes (which we have not time to go into this
evening) this dense mass of vegetable matter became converted into coal.
After a time the shales and sandstones which had been piled above this
stuff, which was to form coal for the future, were again elevated to
form a land surface; upon this another forest sprang up, and by its
decay produced another mass of vegetable matter fit to form coal. This
again was let down below the water, more shales and sandstones were
deposited on the top, and this process went on over and over again till
the whole mass of our present coal measures was formed. You will now see
how it is that trees are so seldom found in an upright position in the
coal beds. As the land went down, they would in very many cases be
toppled over by the water as it flowed against them, or their base would
be rotted, and they would then either fall or be blown over; that is the
reason why in most cases they are found lying flat on the roof of the
coal bed. But in a few cases, when the depression was very gentle and
gradual, the trees were not overthrown, and the shales and sandstones
accumulated round them and preserved them in the position in which they
grew.
I do not know that I can point out to you anything nowadays that exactly
resembles the state of things that must have gone on during the times
these coal measures were being formed; but there are a great many cases
strikingly analogous to them. I shall not attempt to describe them to
you, but may just mention the mangrove swamps that very often fringe the
coasts in the tropics, and the cypress swamps of the Mississippi, which
are so well described by Sir Charles Lyell in his recent works; also
the great Dismal Swamp of Virginia, which appears to me to furnish the
nearest analogue to the state of things that existed during coal measure
times.
Having explained the way in which coal measures have been formed, we
will now take a brief sketch of its uses and products. The year 1259 is
memorable in the annals of coal mining. Hitherto the mineral had not
been raised by authority, but in that year Henry III. granted a charter
to the freemen of Newcastle-on-Tyne for liberty to dig coal, and a
considerable export trade was established with London, and it speedily
became an article among the various manufacturers of the metropolis. But
its popularity was but short lived. An impression became general
that the smoke arising therefrom contaminated the atmosphere and was
injurious to public health. Years of experience have proved the fallacy
of the imputation; but in 1306 the outcry became so general that a
proclamation was issued by Edward I forbidding the use of the offending
fuel, and authorizing the destruction of all furnaces, etc., of those
persons who should persist in using it. Prejudice gradually gave way as
the value of the fossil fuel became better known, and from that time
downward its use has become more and more extended down to the enormous
extent of our present trade. The annual increase in the production of
coal in the British Isles since the year 1854 is over 21/2 million tons.
In that year the coal produce was about 65 million tons, and it has
grown up to the year 1880 to the grand total of 135 million tons.
We will now deal with some of the uses that this valuable black diamond
is now being put to. It is, in the first place, the center of all our
enterprise and prosperity, and upon it depends our chief success as a
manufacturing nation for the future. When it is exhausted we shall have
to look forward to the condition of things which now obtains in those
regions where there is no coal--that is to say, instead of our being a
nation full of manufacturing and mercantile enterprise, a great nation
to which all the people of the earth resort, we shall be merely a people
who live for ourselves by the cultivation of the ground. The duration of
our coal fields has been ascertained within certain limits. Mr. Hall, an
accomplished geologist, tells us that in England at the present time we
have a stock of coal sufficient for our consumption for no less than
1,000 years. On the other hand, Professor Jevons, whose opinion is
worthy of the very greatest weight on such questions, calculates that
100 years is about the tenure of our coal fields, according to the
present rate of increase in the consumption. Whichever view we take,
sooner or later the end must ultimately come when the coal will be
exhausted; when the great mainspring of our commercial enterprise will
be gone, and we shall revert to that condition in which we were before
the coal fields were worked. In this point of view, therefore, coal has
an especial interest to us as engineers. If coal is important in this
direction, it is no less important in a purely scientific point of view,
apart from any mercantile end.
The chemist or physicist will tell you the wondrous story that the black
substance which you burn is simply so much light and heat and motion
borrowed from the sun and invested in the tissues of plants. He will
tell you that when you sit round your firesides the flame which enlivens
you, and the gas which enables you to read, and which civilizes you, is
nothing in the world but so much sunlight and so much sunheat bottled up
in the tissues of vegetables, and simply reproduced in your grates and
gas burners. Very few persons, I am afraid, realize this, which is one
of the many stories which science in its higher teachings shows us--one
of those fairy tales which are the result of the most careful scientific
investigation. Of the hundred and odd million tons of coal which we in
this country burn in the course of a year, about 20,000,000 tons are
thrown on our house fires; 30,000,000 tons find their way into our blast
furnaces, or are otherwise used in the smelting and manufacture of
metals; about 48,000,000 are burnt under steam boilers; 6,000,000 are
used in gas-making; while the remainder is consumed in potteries, glass
works, brick and lime kilns, chemical works, and other sundries which I
need not speak of.
To go into the chemistry of coal is quite sufficient to take up more
time than I have at my disposal this evening, therefore I will briefly
touch on a few of the main points. Coal gas is made, as you are all
aware, by heating coal or cannel, which is the special form of coal
most valued for the purpose, on account of the high quality of gas it
produces in cylindrical fireclay retorts.
The by-products obtained in the manufacture of coal gas, the tar and the
ammonia water, are nowadays scarcely less important than the coal gas
itself. The ammonia water furnishes large quantities of salts to be
used, among other applications, as food for plants. We thus restore
to-day to our vegetation the nitrogen which existed in plants of
primeval times. The tar, black and noisome though it be, is a marvelous
product, by the reason of scores of beautiful substances which are
concealed within it.
Coal tar when distilled yields three main products: naphtha, dead oil,
and pitch or asphalt. The naphtha on redistillation yields benzine, from
which are prepared some of our most beautiful dyes; the dead oil, as
the less volatile portion is termed, furnishes carbolic acid, used as a
disinfectant and antiseptic, together with anthracene and naphthaline;
all three substances the starting points of new series of coloring
matters.
This discovery of these coloring matters marks an era in the history
of chemical science; it exercised an extraordinary influence on the
development of organic chemistry. Theoretical and applied chemistry were
knit together in closer union than ever, and dye followed dye in quick
succession; after mauve came magenta, and in close attendance followed a
brilliant train of reds, yellows, oranges, greens, blues, and violets;
in fact, all the simple and beautiful colors of the rainbow.
But there is still another story of coal tar to be told. Among the
many curious substances that wonderful fluid contains is the beautiful
wax-like body called paraffine, the development of which chiefly owes
its origin to the genius and energy of Mr. James Young. As early as
1848, Mr. Young had worked a small petroleum spring in a coal mine in
Derbyshire, and had produced oils suitable for burning and lubricating
purposes, but the spring gave out, and then Mr. Young sought to obtain
these oils by distilling coal. After many trials, in conjunction with
other gentlemen connected therewith, he proved successful, and the
present magnitude of this industry is without parallel in the history of
British manufactures.
In Scotland alone there are about sixty paraffine oil works, one alone
occupying a site of nearly forty acres. Here about 120,000 gallons of
crude oil are produced weekly, and among the various works in Scotland
about 800,000 tons of shale are distilled per annum, producing nearly
30,000,000 gallons of crude oil, from which about 12,000,000 gallons of
refined burning oil are obtained in addition to the large quantities
of naphtha, solid paraffine, ammonia, and other chemical products.
Twenty-five years ago scarcely a dozen persons had seen this paraffine,
and now it is turned out by the ton, fashioned into candles delicately
tinted with colors obtained from coal tar.
I might dwell on this subject until it becomes wearisome to you,
therefore I will not trespass too much on your time. But from every
point we look we reach this fact, that our coal trade is one which
develops itself according to laws that we are perfectly powerless to
control; if it seems to promise a less rapid increase here, it is only
that it may spread abroad with accelerated vigor elsewhere; if it is our
slave in some aspects, it seems as if it were our master in others.
Finally, we have to ask, What of our export coals? Rapid as has been the
growth of our total production during the last twenty-three years, the
growth of our export of coals has been greater still. Beginning at
4,300,000 tons in '54, we find it reaching 16,250,000 tons in '76, and
an increase at a corresponding ratio up to the present date as far as
statistics will carry us. At such a rate of increase it would seem as
if our whole annual production would be ultimately swallowed up in our
exports, and it is not, perhaps, impossible that after we have ceased to
be to any great extent a manufacturing people, a certain export trade
in coal may still continue. Just the same as the export trade in coal
preceded by centuries our own uses for it other than domestic, so may
it also survive these by a period as prolonged. If our descent from
our present favored position be a gradual one, much may be done in the
interval to adapt ourselves to the future outcome, but it is certain
that nothing will be done except under the stern persuasion of
necessity.
When our coal fields become exhausted, be it soon or late, he would be
a wise or, perhaps, a rash speculator who fixed himself to a year or a
generation. Being inevitable, the best philosophy is to make our decline
more gradual and less bitter. Sentimental regrets that these hills and
valleys will no longer resound with the din of labor, or be blackened by
the smoke of the factory, would surely be out of place. What we might
regret is that Britain, which we know and are proud of, the Britain
of great achievements in politics and literature, of free thought and
self-respecting obedience, of a thousand years of high endeavor and
constant progress, was indeed to perish when these factories and
furnaces whirled and blazed their last. But, it is not so. This
country's fortunes are gradually being merged into those of a Greater
Britain, which largely, through the aid of coal, whose prospective
loss we are lamenting, has grown beyond the limits of these islands to
overspread the vastest and richest regions of the earth; and we have no
reason to fear that the great inheritance that America and Australia
and New Zealand have accepted from us will in their hands be dealt
unworthily with in the future.
* * * * *
GASTON PLANTE.
This eminent scientist was born in Orthez (Department of
Basses-Pyrenees) on the 22d of April, 1834; at present in his fiftieth
year. He began his scientific career as assistant to Edmund Becquerel at
the Conservatoire des Arts et Metiers at Paris. In the year 1859, after
resigning his position at the above named institution, he entered upon
his researches in electricity, and has continued them ever since.
His work entitled "Recherches sur l'Electricite" is a model of clear
language and elegant demonstration, and contains all the papers
presented by Plante to the Paris Academy of Sciences since 1859.
[Illustration: GASTON PLANTE.]
At the Paris Electrical Exhibition in 1881, Plante received a Diploma
of Honor, the highest distinction conferred, while in the same year the
Academy of Sciences voted him the "Lacaze" prize, and the Society for
the Encouragement of National Industry presented him with the "Ampere"
medal, its highest award.
Plante deserves not only the honors conferred upon him by his own
country, but those of the world on account of his cosmopolitan
character--a rarity among his countrymen. He sends his apparatus to all
exhibitions of any consequence; they appeared at Munich and Vienna,
where their interpretation by the attendant added considerably to the
renown of their author.--_Zeitch f. Elektrotechnik_.
* * * * *
WARREN COLBURN.
Warren Colburn, the eminent American mathematician, was born in Dedham,
Mass., March 1, 1793.
He was the eldest son of a large family of children. His parents were
poor, and "Warren" was, during his childhood, frequently employed in
different manufacturing establishments to aid the family by his small
earnings.
In early boyhood he manifested an unusual taste for mathematics, and
in the common district school was regarded as remarkable in this
department. He learned the trade of a machinist, studying winters, until
he was over twenty-two years of age, when he began to fit for Harvard
College, which he entered in 1817 and graduated with high honors in
1820. He taught school in the winter months, while in college, in
Boston, Leominster, and in Canton, Mass. From 1820 to 1823 he taught a
select school in Boston.
While in college he was regarded as by far the best mathematician in his
class, and during this period thought there was the necessity for such a
book as his "First Lessons in Intellectual Arithmetic." This conviction
had been forced upon his mind by his experience in teaching. In the
autumn of 1821 he published his "first edition." His plan was well
digested, although he was accustomed to say that "the pupils who were
under his tuition made his arithmetic for him;" that the questions they
asked and the necessary answers and explanations which he gave in reply
were embodied in the book, which has had a sale unprecedented for
any book on elementary arithmetic in the world, having reached over
2,000,000 copies in this country, and the sale still continues, both in
this country and in Great Britain. It has been translated into most of
the European languages and by missionaries into many Asiatic languages.
After teaching in Boston about two and one-half years, he was chosen
superintendent of the Boston Manufacturing Company's works at Waltham,
Mass., and accepted the position; and in August, 1824, owing to the
mechanical genius he displayed in applying power to machinery, combined
with his great administrative ability, he was appointed superintendent
of the Lowell Merrimac Manufacturing Co., at Lowell, Mass. Here he
projected a system of lectures of an instructive character, presenting
commerce and useful subjects in such a way as to gain attention and
enlighten the people.
For several years he delivered gratuitous lectures on the Natural
History of Animals, Light, Electricity, the Seasons, Hydraulics,
Eclipses, etc. His knowledge of machinery enabled him admirably to
illustrate these lectures by models of his own construction; and his
successful experiments and simple teaching added much to the practical
knowledge of his operatives.
He proposed to occupy the space between the common schools and the
college halls by carrying, so far as might be practicable, the design of
the Rumford Lectures of Harvard into the community of the actual workers
of common life.
In the mean time he discharged his official duties efficiently, and the
superintendence of the schools of Lowell was also added to his labors.
He never relinquished, during these busy years, the design formed in his
college days of furnishing to the children of the country a series of
text-books on the _inductive plan_ in mathematics.
His "Algebra upon the Inductive Method of Instruction," appeared in
1825, and his "Sequel to Intellectual Arithmetic" in 1836. He regarded
the "Sequel" as a book of more merit and importance than the "First
Lessons."
He also published a series of selections from Miss Edgeworth's stories,
in a suitable form for reading exercises for the younger classes of
the Lowell schools, in the use of which the teachers were carefully
instructed.
In May, 1827, he was elected a Fellow of the American Academy of
Sciences. For several years he was a member of the Examining Committee
for Mathematics at Harvard College.
He was a member of the Superintending School Committee of Lowell; and so
busy were he and his coworkers that they were repeatedly obliged to hold
their meetings at six o'clock in the morning.
Warren Colburn was ardently admired--almost revered--by the teachers who
were trained to use his "Inductive Methods of Instruction" in teaching
elementary mathematics.
In personal appearance Mr. Colburn was decidedly pleasing. His height
was five feet ten, and his figure was well proportioned. His face
was one not to be forgotten; it indicated sweetness of disposition,
benevolence, intelligence, and refinement. His mental operations were
not rapid, and it was only by great patience and long continued thought
that he achieved his objects. He was not fluent in conversation; his
hesitancy of speech, however, was not so great when with friends as
with strangers. The tendency of his mind was toward the practical in
knowledge; his study was to simplify science, and to make it accessible
to common minds.
Mr. Colburn will live in educational history as the author of "Warren
Colburn's First Lessons," one of the very best books ever written, and
which, for a quarter of a century, was in almost universal use as a
text-book in the best common schools, not only in the primary and
intermediate grades, but also in the grammar school classes.
In accordance with the method of this famous book, the pupils were
taught in a natural way, a knowledge of the fundamental principles of
arithmetic. By its use they developed the ability to solve mentally and
with great facility all of the simple questions likely to occur in the
every day business of common life.
Undoubtedly Pestalozzi first conceived the idea of the true "inductive
method" of teaching numbers; but it was Mr. Colburn who adapted it to
the needs of the children of the common elementary schools. It has
wrought a great change in teaching, and placed Warren Colburn on the
roll as one of the educational benefactors of his age.
He died at Lowell, Mass., Sept. 13, 1883, at the age of 90
years.--_Journal of Education_.
* * * * *
THURY'S DYNAMO-ELECTRIC MACHINE.
Thury's dynamo-electric machine, which presents some peculiarities,
has never to our knowledge been employed outside of Sweden and a few
neighboring regions; but this is doubtless due to some personal motive
or other of its constructors, since it has, it would seem, given
excellent results in every application that has been made of it. It is
represented in perspective in Fig. 1, and in longitudinal section and
elevation in Figs. 2 and 3.
As may be seen, it is a multipolar (6-pole) machine in which an attempt
has been made to utilize magnetically, as far as possible, all the iron
used in the frame. For this reason the system has been given the form of
a hexagonal prism, whose faces are formed of flat electro-magnets, A, A,
xxx, constituting the inductors.
The internal angles of this prism are filled by polar expansions, P, P,
xxx, alternately north and south, that thus form in the interior of the
apparatus an inscribed cylinder designed to receive the armature. This
latter belongs to the kinds that are wound upon a cylinder in which the
wire is external thereto.
The conductors are placed upon the iron drum longitudinally and parallel
with its axis. But instead of being connected with each other at the
posterier end of the armature, as in the Siemens system, they are
connected according to chords that correspond to a fourth, a sixth,
or any equal fraction whatever of the circumference. Fig. 4 gives a
perspective view of the cylinder, upon which the conductors 1, 2, 3,
4, and so on, are placed according to generatrices. The armature is
supposed to be divided into six parts, each conductor passing over the
bases of the drum through a chord equal to the radius, that is to say,
corresponding to a sixth of the circumference.
Three conductors are all connected together in such a way as to form
but a single circuit closed upon itself. Conductor 1, for example, is
connected with No. 6 in such a way that the end issuing from 1 becomes
the end that enters No. 6. Conductor No. 3 is connected in the same way
with No. 8, and so on, up to the last conductor, which is connected in
its turn with the end that enters the first.
As the figure shows, the conductor before passing from 3 to 8, for
example, returns several times upon itself in following 6 and 3, and the
same is the case with all the rest of the winding.
[Illustration: FIG. 1. PERSPECTIVE VIEW OF THE THURY MACHINE.]
In this way the cylinder becomes inclosed within nine rectangular wire
frames, each of which is connected with the following one by a conductor
that is at the same time connected with one of the nine plates of
the collector. The number of the rubbers corresponds to that of the
inducting poles. They may be coupled in different ways, but they are in
most cases united for quantity.
It will be seen that the Thury armature resembles, in the system of
winding, those of the Siemens machines and their derivatives. But it
differs from these, however, in the details connected with the coupling
of the wires, from the very fact that the features of a two-pole machine
are not found exactly in a multipolar one.
[Illustration: FIGS. 2 AND 3.]
This latter kind of machine is considered advantageous by its inventors,
in that there is no need of revolving it with much velocity. It must not
be forgotten, however, that although we reduce the velocity by this mode
of construction, we are, on another hand, obliged to increase the size
of the machine, so that, according to the circumstances under which we
chanced to be placed, the advantage may now be on the one side and now
on the other.
[Illustration: FIGS. 4 AND 5.]
It goes without saying that Fig. 4 is essentially diagrammatic, and is
designed to give a clearer idea of the mode of winding the armature. In
practice the number of the frames, and consequently that of the plates
of the conductor, is much greater, and the arrangement that we have
described is repeated a certain number of times, the conducter always
forming a circuit that is closed upon itself.
The Thury machines are constructed in different styles. No. 1 is a
100-lamp (16 candles and 100 volts) machine, and Nos. 2 and 3 are
nominally 250-lamp ones, but may be more. Their weight is 1,100
kilogrammes, and their velocity, for 100 volts, is from 400 to 500
revolutions, according to the mode of coupling.
A later type, now in course of construction, is to furnish from 750 to
2,000 lamps, with 250 revolutions, for 100 volts, and is not to weigh
more than 2,000 kilogrammes. Let us add that Messrs. Meuron and Cuenod,
the manufacturers, have likewise applied their mode of winding to
conductors arranged radially upon the surface of a circle. Fig. 5 shows
this arrangement.
In this case the inductors will, it is unnecessary to say, be arranged
laterally as in all flat ring machines. The arrangement will recall, for
example, that of the Victoria machines (Brush-Mordey).
We do not think that the inventors have applied this radial arrangement
practically, for it does not appear to be advantageous. The parts of
conductors which are perpendicular to the radius, and which can be only
inert (even if they do not become the seat of disadvantageous currents),
have, in fact, too great an importance with respect to the radial
parts.--_A. Guerout, in La Lumiere Electrique_.
* * * * *
BREGUET'S TELEPHONE.
Prof. G. Forbes gives the following description: The instrument which
I call Breguet's telephone is founded upon the instrument which was
described by Lipmann, called the capillary electrometer. The phenomenon
may be shown in a variety of ways. One of the easiest methods to show it
is by taking a long glass tube and bending it into two glasses of dilute
acid, and, the tube being filled with acid itself, a piece of mercury
is placed in the center of the tube. Then if one pole of a battery is
connected with one vessel of acid, and the other pole of the battery is
connected with the other vessel of acid, at the moment of connection the
bit of mercury will be seen to travel to the right or left, according to
the direction of the current. M. Lipmann explained the action by showing
that the electro-motive force which is generated tends to alter the
convexity of the surface of the mercury. The surface of the mercury,
looked at from one side, has a convex form, which is altered by the
electro-motive force set up when connection is made with the battery.
The equilibrium of the mercury is dependent upon the convexity, and
consequently when the convexity is disturbed the mercury moves to one
side or the other. Lipmann also showed that if a tube containing a bit
of mercury, and tapering to a point, is taken and dipped into acid, and
then the tube filled with acid, on one pole of a battery being dipped
into the tube and another into the acid the mercury will move up or
down, showing similar action to that which I have just described.
Lipmann further showed the reverse effect, that if a piece of mercury be
forcibly pressed, so as to alter the convexity of its surface, such
as by bringing it into a narrower part of the tube, then there is an
electro-motive force produced.
It occurred to me, and no doubt it did to Breguet also, that if we speak
either against the surface of the glass tube, and caused the tube to
vibrate, or if the mercury were caused to vibrate in the manner I have
shown, we ought to be able to introduce a varying current in the wires
which might have sufficient electro-motive force to produce audible
speech in a Bell telephone. Further, the same instrument, since varying
electro-motive force affected the drop of mercury and produced varying
displacement, ought also to act as a receiving instrument, and should
vibrate in accordance with the currents that arrive. My experiments
have only been in the way of using the instrument as a transmitter; but
Breguet, I find, used it as a receiver as well as a transmitter, though
I am not aware that M. Breguet made any actual experiments so as to
produce articulate speech. I presume that this was done, although I have
not come across any description of the experiments, and it was for that
reason that I thought possibly some account of my own experiments might
be interesting to the members of the Society. The first tubes that I
used were bits of glass tube about a centimeter diameter, and simply
drawn out to a tapering point. I have the tubes here. The first
experiment I tried was by tapping the glass tube so as to mechanically
shift the position of the mercury, and by listening on the telephone for
the effect. For a long time, at least an hour, I could get no effect at
all. At last I got a sound, but could not understand how it was that at
one time of tapping I could not hear, while at another time it was quite
loud.
At the top I always got sound, but at the side I got no sound, although
the mercury was shaking. I then tried to see how feeble a current was
audible in the telephone. An assistant tapped the tube while I stood out
of the way, and where I could not see. I got him to tap it gentler and
gentler, and could hear the most feeble tap. A pellet of paper was next
dropped from various heights down to an inch, and each tap was perfectly
audible in the telephone. I tried many methods, and one, purely
accidentally chosen, was a piece of glass tube which I had drawn out
into a tube about 2 mm. diameter, and then nearly closed the end of
it. I have that tube here, and you will see what an ill-shapen and
ugly-looking tube it is, but it is one of the best tubes I ever got; and
finally, I found that small bits of thermometer tube, which were simply
closed at their ends with a blow-pipe, gave very good results, and I was
able to make them useful for various purposes. I then tried mounting a
tube on the end of a speaking-trumpet and speaking to the mercury, but
got no effect. In every place where I attached the glass tube itself
to a sounding-board I got a very accurate reproduction. I put one on a
piece of ferrotype plate, and that gave really the best result I ever
got. The tube was fastened with sealing-wax, and with it I got excellent
speech heard in a Bell receiver. I tried putting in a large number of
these tubes, all in quantity, on the bottom of a ferrotype plate, but
with no advantage. I have not yet tried putting them in series, one
behind the other, so as to increase the electro-motive force, but I
think that probably would be an improvement; of course it would require
many vessels of acidulated water to dip into. The most distinct
articulate speech was obtained from an ordinary ferrotype telephone
plate, secured at the edges, and one of the glass tubes you see here
attached to it.
* * * * *
MUNRO'S TELEPHONIC EXPERIMENTS.
Mr. J. Munro, whose name is well known not only as a very clear writer
upon electrical subjects, but as an original investigator, has recently,
with the assistance of Mr. Benjamin Warwick, been conducting a most
interesting experimental investigation of the action of the microphone
as a telephonic transmitter, with the result of proving that metals may
advantageously be employed in the place of carbon in a transmitting
instrument, a practical development of one of the very earliest of
Professor Hughes' microphones. The fact that metallic electrodes can
practically be employed in microphonic transmitters has been denied of
late with so much assurance and in such high quarters, that Mr. Munro's
successful applications of that portion of Professor Hughes' discovery
possess an especial interest, and must to a considerable extent affect
the aspect of litigation in future contests in which the discovery of
the microphone and the invention of the carbon transmitter are vital
points at issue.
In investigating the properties of metallic conductors employed in the
construction of microphones, Mr. Munro's first experiments were made
with wires. These, in some cases, were caused by the action of a
diaphragm, to rub the one on the other in such a manner as to make the
point of contact vary (under the influence of the vibrations of the
diaphragms) on one side or other of a position of normal potential, so
that by the movement of a wire attached to a vibrating tympan along a
fixed wire conveying a current from a battery, and thereby shunting the
current at various positions along the length of the fixed wire, the
strength of the current in the derived circuit, in which was included a
suitable receiver, was varied accordingly. In other experiments mercury
was employed, either as a sliding-drop, inclosing the fixed wire, or as
an oscillating column; but these experiments, though instructive and
interesting, did not for various reasons give encouraging results with a
view to the practical application of the principle.
They, however, led Mr. Munro to proceed with compound wire structures,
such as gratings resting upon or rubbing against one another, and one of
the first experiments in this direction proved very successful, and led
Mr. Munro to the construction of his gauze telephone, which is the most
characteristic and efficient of his practical apparatus.
This instrument consists essentially of two pieces of iron-wire gauze,
the one fixed in a vertical plane, and the other resting more or less
lightly against it, the pressure between them being regulated by an
adjustable spring or weight. These gauze plates are so connected in a
telephonic circuit as to constitute the electrodes of a microphone; for
touching one another lightly in several points, they allow the current
to be transmitted between them in inverse proportion to the resistance
offered to it in its passage from one to the other. Under the influence
of sonorous vibrations the one plate dances more or less on the other,
thus varying the resistance; and very perfect articulation is produced
in a telephonic receiver included in the circuit. The gauze transmitter
so constructed may be fixed within a wall-box with or without a
mouthpiece; but as the sound waves acting directly upon the gauze plates
set them into agitation through their sympathetic vibration or by direct
impact, no sort of diaphragm or equivalent device is necessary, and none
is employed.
[Illustration: FIG. 1.]
A convenient form of this apparatus is shown in Fig. 1, and to which the
name of "The Lyre Telephone" has been given from its resemblance to that
impossible musical instrument. In this apparatus, G is a plate of iron
wire gauze stretched vertically between two horizontal wires attached to
a lyre-shaped framework of mahogany; against the plate rests the smaller
plate, G squared, the normal pressure between them being regulated by an
adjustable spring acting in opposition to a weighted lever, W. The two
plates are connected respectively with the attachment screws, X and
Y, by which the instrument is placed in a circuit with a battery and
telephonic circuit.
[Illustration: FIG. 2.]
A modification of this apparatus is shown in the diagram sketch, Fig.
2, which will probably be a more practical form. In this instrument the
electrodes consist of two circular disks of iron wire gauze of different
diameters, the larger disk, G, which is fixed, being pierced with holes
of smaller diameter than the smaller disk, G squared. In the diagram the two
disks are shown separated for the purpose of explanation, but in reality
they rest the one against the other; the smaller and movable disk,
G squared, is held up against G with greater or less pressure by the spiral
spring, S, the tension of which can be adjusted by a screw or other
suitable device at N. This form of the apparatus is more suitable for
inclosure in a wall box with or without a mouthpiece, but it does not
require the employment of any kind of diaphragm or tympan. Mr. Munro
can employ with all his instruments an induction coil for installations
where the resistance of the line wire makes it desirable to do so; the
microphone and battery being included in the primary circuit and the
telephones in the secondary.
[Illustration: FIG. 3.]
Fig. 3 is an ingenious arrangement devised by Mr. Munro, in which the
adjusting spring or weight is substituted by a magnet which may be
either a permanent or an electro-magnet. The figure shows an arrangement
in which the fixed gauze, g, is perforated as in the apparatus
illustrated in Fig. 2, and the movable electrode, g, is bent or dished
so as to press upon g around its edge. E is a magnet which by its
attractive influence upon g holds t up against g with a pressure
dependent upon its magnetic intensity and upon its distance from the
gauze. By making E an electro-magnet, and including its coil in the
telephonic circuit, an instrument may be constructed in which the normal
pressure between the electrodes can be automatically adjusted to the
strength of the current, and in cases where an induction coil is
employed the magnet, E, may be the core of such a coil.
[Illustration: FIG. 4.]
Fig. 4 illustrates an apparatus devised by Mr. Munro, and to which the
name thermo-microphone might be given, as it is a microphone in which
thermo-electric currents are employed in the place of voltaic currents,
its special feature of interest lying in the fact that the heated
junction of the thermo-electric couple is identical with the microphone
contacts of the two electrodes. In this very elegant experiment a piece
of iron wire gauze, G, is supported in a horizontal position by a light
metallic support, B. To another support. A, is loosely hinged a frame,
which at its further extremity carries a little coil of German silver
wire, C, which by its weight rests upon the center of the gauze plate,
G; and in contact therewith, and to increase the pressure of contact, a
little bar weight is laid within the convolutions of the core. The
two electrodes, the gauze, and the coil are connected, as shown, to a
receiving telephone, T. Upon the application of heat, as from the flame
of a spirit lamp placed below, a thermo-electric current is set up
throughout the circuit; in this condition the apparatus becomes a very
perfect microphone, and when the pressure between the electrodes is
properly adjusted it is a very efficient telephonic transmitter,
transmitting articulate speech and musical sounds with remarkable
clearness and fidelity.
[Illustration: FIG. 5]
Mr. Munro is, with the aid of Mr. Warwick's manipulative skill,
extending this portion of his investigation further by experimenting
with gauzes and coils of various metals forming other couples in
the thermo-electric series, as well as with iron and other gauzes
electrotyped with bismuth and other metals, and we hope in due time to
lay the results of those experiments before our readers.
Mr. Munro has, moreover, observed that if two pieces of gauze of
identical material and in microphonic contact be heated, a peculiar
sighing sound is heard in a telephone connected with them and with a
battery, and he attributes this phenomenon to the electrical discharge
between the gauze plates being facilitated and increased by the
action of heat, but we are rather inclined to trace the effect to the
mechanical action of the one gauze moving over the other under the
influence of expansion and contraction of the metals by the variable
temperature of the flame and convection currents of heated air, such
movement producing the sounds just as would be produced if one of the
electrodes of an ordinary microphone were as delicately moved by the
hand or other agent.
[Illustration: FIG. 6]
Figs. 5 and 6 illustrate another and distinct form of metallic
microphone transmitter designed by Mr. Munro and Mr. Warwick, in which
a small chain, preferably of iron, forms the microphonic portion of the
apparatus. In Fig. 5, A is a plate of sonorous wood forming a diaphragm
or collector of the sonorous waves; to the back of this is attached a
short length of chain, C, the opposite ends of which are by the wires, X
and Y, included in the telephonic circuit. The points of junction of the
links with one another constitute the variable microphonic contacts, and
the normal pressure between them is adjusted by the spiral spring, S,
the tension of which may be varied by the cord and winding pin, B. Fig.
6 is the section of a transmitter constructed upon this principle, and
in which two chains, c and c', are employed attached at one end by a
wire, f, to a diaphragm mouthpiece, N, and at their opposite extremities
to the adjusting springs, s and s'; an induction coil, D, may be
employed if the resistance of the line render it advantageous.
[Illustration: FIG. 7]
Fig. 7 is a form of pencil microphone experimented with by Mr. Munro,
which differs from some of the Hughes' transmitters adopted by Crossley,
Gower, Ader, and many others only in the material of which it is
composed, Mr. Munro's being of cast iron, while the others to which we
have referred are of carbon rods such as are used in electric lighting.
In Fig. 7 a light cast-iron bar, i squared, of the form shown, is supported in
holes drilled in two blocks of cast iron, i i', and the pressure between
the bar and the blocks can be adjusted by a regulating spring, s. In
connection with this apparatus Mr. Munro has observed that rust has no
appreciable effect upon the efficiency of the instrument unless it be
to such an extent as to cause the two to adhere, or to be "rusted up"
together.
[Illustration: FIG. 8]
We now come to another class of metallic transmitters with which Mr.
Munro and his associate have been making experiments, and to which he
has given the name "Grain transmitter," since it consists of a box
having metallic sides, e e', to which terminal screws, t t', are
attached and filled in between with iron or brass filings, granules of
spongy iron, or indeed small metallic particles in any form; one of the
most efficient transmitters being a box such as is shown in Fig. 8,
filled with a quantity of 1/4 in. screws.
[Illustration: FIG. 9]
The results of Mr. Munro's experiments have led him to the opinion
that the action of the microphone must be attributed to the action
of sonorous vibrations upon the air or gaseous medium separating the
so-called contact-points of the electrodes, and that across these
spaces, or films of gaseous matter, silent electrical discharges take
place, the strengths of which, being determined by the thickness of the
gaseous strata through which they pass, vary with the motion of the
electrodes; and as, according to this hypothesis, the distances of the
electrodes from one another is determined by the sound-waves, the sound
in that way controls the current.--_Engineering_.
* * * * *
APPARATUS FOR MANEUVRING BICHROMATE OF POTASSA PILES FROM A DISTANCE.
Bichromate of potassa piles, especially those single liquid ones that
are applied to domestic lighting, all present the grave defect of
consuming almost as much zinc in open as in closed circuit, and of
becoming rapidly exhausted if care be not taken to remove the zinc from
the liquid when the battery is not in use. This operation, which is a
purely mechanical one, has hitherto required the pile to be located near
the place where it was to be used, or to have at one's disposal a system
of mechanical transmission that was complicated and not very ornamental.
In order to do away with this inconvenience, which is inherent to all
bichromate piles, Mr. G. Mareschal has invented and had constructed an
ingenious system that we shall now describe.
[Illustration: FIG. 1.--BICHROMATE OF POTASSIUM PILE, WITH MANEUVERING
APPARATUS.]
Mr. Mareschal's plan consists in suspending the frame that carries all
the battery zincs (Fig. 1) from the extremity of a horizontal beam, and
balancing them by means of weights at the other extremity.
The system, being balanced, the lifting or immersion of the zincs then
only requires a slight mechanical power, such as may be obtained from
an ordinary kitchen jack through a combination that will be readily
understood upon reference to Fig. 2. The axis, M, of the jack,
on revolving, carries along a crank, MD, to which is fixed a
connecting-rod, A, whose other extremity is attached to the horizontal
beam that supports the zincs and counterpoises. If the axle, M, be given
a continuous revolution, it will communicate to the rod, A, an upward
and downward motion that will be transmitted to the beam and produce an
alternate immersion and emersion of the zincs.
Upon stopping the jack at certain properly selected positions of the
rod, MD, the zincs may, at will, be kept immersed in the liquids, or
_vice versa_. This is brought about by Mr. Mareschal in the following
way: The jack carries along in its motion a horizontal fly-wheel, V,
against whose rim there bears an iron shoe, F, placed opposite an
electro-magnet, E. In the ordinary position, this shoe, which is fixed
to a spring, bears against the felly of the wheel and stops the jack
through friction. When a current is sent into the electro-magnet, E, the
brake shoe, F, is attracted, leaves the fly wheel, and sets free the
jack, which continues to revolve until the current ceases to pass into
the electro.
[Illustration: FIG. 2.--PRINCIPLE OF THE APPARATUS.]
The problem, then, is reduced to sending a current into the electro and
in shutting it off at the proper moment. This result is obtained very
simply by means of an auxiliary Leclauche pile. (The piles got up for
house bells will answer.) The current from this pile is cut off from
the electro, F, by means of a button, B, when it is desired to light or
extinguish the lamps. In a position of rest, for example, the crank, MD,
is vertical, as shown in the diagram to the right in Fig. 2. The circuit
is open between M and N through the effect of the small rod, C, which
separates the spring, R, from the spring, R'. As soon as the circuit has
been closed, be it only for an instant, the crank leaves its vertical
position, the rod, C, quits the bend, S, and the spring, R, by virtue of
its elasticity, touches the spring, R', and continues its contact until
the crank, MD, having made a half revolution, the rod, C', repulses the
spring, R, and breaks the circuit anew. The brake then acts, and the
crank stops after making a revolution of 180 deg., and immersing the
zincs to a maximum depth. In order to extinguish the lamp, it is only
necessary to press the button, B, again. The axle, M, will then make
another half revolution, and, when it stops, the zinks will be entirely
out of the liquid. The depth of immersion is regulated by fixing the
crank-pin. D, in the apertures, T1, or T2, of the connecting rod. This
permits the travel, and consequently the degree of immersion, to be
varied.
The device requires three wires, two for connecting the lamp with the
battery, and one for maneuvering the apparatus through a closing of the
contact, B.
With Mr. Mareschal's system, bichromate of potassa piles may be utilized
in a large number of cases where a light of but short duration is
required until the battery is exhausted, without the tedious maneuvering
of a winch and without inconvenience. The jack permits of a large number
of lightings and extinctions being effected before it becomes necessary
to wind up its clockwork movement. This operation, however, is very
simple, and may be performed every time the battery is visited in order
to see what state it is in.
We regard Mr. Mareschal's apparatus as an indispensable addition to
every case of domestic electric lighting in which bichromate of potassa
piles are used, and, in general, to all cases where the pile becomes
uselessly exhausted in open circuit. It will likewise find an
application in laboratories, where the bichromate pile is in much demand
because of its powerful qualities, and where it is often necessary to
order it from quite a distant point.--_La Nature_.
* * * * *
MAGNETIC ROTATIONS.
By E. L. VOICE.
The remarkable researches and experiments of Professor Hughes clearly
show that magnetism is totally independent of iron, and that its
molecules, particles, or polarities are capable of rotation in that
metal. It would also appear that by reason of the friction between
magnetism and iron, the molecules of the latter are only partially
moved, such movement being the result of the tendency of iron to retard
magnetic change.
I have found that the magnetic molecules also possess inertia, that they
are capable of acquiring momentum, and that their rotation continues
for a considerable time after the exciting cause of their rotation has
ceased.
These facts may be proved in a very evident manner, inasmuch as induced
electric currents are generated by this _after_ rotation, which may be
made to light incandescent lamps.
In this case the magnetic rotations are produced in an electro magnet by
means of alternate currents supplied by alternating Gramme machine.
In order to better explain the action, it will be necessary to refer
to a new electro-motor, which was the subject of an article in the
_Electrical Review_ of February 19 last. It is of that type of motor in
which the field magnet and armature poles are alternately arranged, and
which requires a periodical reversibility of magnetism in the armature
to cause the latter to revolve, as in the Griscom motor. The insulating
strips in the commutator are sufficiently wide to demagnetize the whole
of the machine before reversibility in the armature takes place, and
this demagnetization sets up a _direct_ induced current, which is caught
in a shunt circuit by the aid of a second commutator, which only comes
into action when the first commutator goes out.
When this motor is supplied by a continuous current, it is easy to
understand that the induced current which passes through the shunt
circuit, and which is caused by the demagnetization, is proportional
to the mass of iron and wire of which the machine is composed, or
proportional to its inductive capacity. This current is purely a
secondary effect, of short duration, and only occurs once at each break
of the commutator.
The motor is of such a size that when supplied with a continuous current
of proper strength the induced electrical effect in the shunt circuit
will light one incandescent lamp. If, however, it is supplied with an
alternating current of the same power, it will light eight lamps, and
the mechanical power given off is even more than with a continuous
current, provided that the alternations from the dynamo do not exceed
6,000 a minute.
At first I was considerably puzzled by this great difference, because in
both cases it is impossible for the lamp circuit to be acted upon by the
main current. It occurred to me, however, that the rapid alternations
of the exciting current from the dynamo, and the consequent speed of
magnetic molecular rotation, gave the latter a certain momentum, and
that by widening the insulating strips of the first or main current
commutator, and proportionately increasing the width of conducting
surface in the shunt commutator up to certain limits, this effect would
be increased. I found such to be the case, from which I inferred that
the increase of induced current in the shunt circuit was on account of
its longer duration, by reason of the acquired momentum of the magnetic
molecular rotations _after_ the alternating exciting current had ceased.
[Illustration]
Those who have facilities for carrying out experiments may prove it in
the following manner:
E, in the inclosed drawing, is an electro-magnet whose brushes press on
two metallic bands, B and B, fixed to but insulated from the spindle,
A. The band, B, is in electrical circuit with the shunt commutator, S,
and the main commutator, M; while the band, B, is in contact with
shunt commutator, S, and main commutator, M. This contact is made
by conducting rods, as indicated. The commutators, as regards their
brushes, are so arranged that when M and M are in action, S and S are
out of action, and _vice versa_. The spindle and commutators are rotated
by the pulley, P. L is an incandescent lamp in the shunt circuit.
Let us now suppose the apparatus at rest, and the brushes in electrical
contact with the main commutators, M and M. The current from an
alternating dynamo passes into the magnet, E, and rapidly reverses its
polarity. By actuating the pulley, P, the commutators are rotated, when
M and M go out of, and the shunt commutators, S and S, come into
action, enabling the _after_ current set up in the magnet to light the
lamp, L, in the shunt circuit.
In order to make comparative tests, the same apparatus may be supplied
with continuous instead of alternating currents. The after current in
the former case, however, is much smaller, consisting of one electrical
impulse only at each break of the commutator, whereas in the alternating
system these impulses are practically continued; the result being that,
all things being equal, a far greater number of lamps may be used in the
shunt than when supplied by continuous current only, and it would
appear that this difference can only be attributed to the fact that the
rotatory motion of magnetic molecules, or polarity of the magnet, E,
acquires momentum when acted upon by a suitable physical cause, such as
alternating currents of electricity; this momentum lasting a sensible
time after the cessation of the acting cause.
If we had the gift of magnetic sight, and could see what is going on in
the electro-magnet when it is excited by alternating currents, we should
probably see the molecules or polarities tumbling over each other at an
enormous rate. I do not think, however, that we should see anything but
a vibratory motion as regards the iron molecules.--_Elec. Review_.
* * * * *
[AMER. MICROSCOP. JOUR.]
LIGHTON'S IMMERSION ILLUMINATOR
The following extremely simple plan for an immersion illuminator was
first brought to the notice of microscopists a few years ago, and,
in the absence of the inventor, was kindly described by Prof. Albert
McCalla, at the meeting of the American Society of Microscopists, at
Columbus, O. It consists of a small disk of silvered plate glass, c,
about one-eighth of an inch thick, which is cemented by glycerine
or some homogeneous immersion medium to the under surface of the
glass-slide, s. Let r represent the silvered surface of the glass disk,
b, the immersion objective, f, the thin glass cover. It will be easily
seen that the ray of light, h, from the mirror or condenser above the
stage will enter the slide and thence be refracted to the silvered
surface of the illuminator, r, whence it is reflected at a corresponding
angle to the object in the focus of the objective. A shield to prevent
unnecessary light from entering the objective can be made of any
material at hand, by taking a strip one inch long and three-fourths
of an inch wide and turning up one end. A hole not more than
three-sixteenths of an inch in diameter should be made at the angle. The
shield should be placed on the upper surface of the slide, so that the
hole will cover the point where the light from the mirror enters the
glass. With this illuminator Moeller's balsam test-plate is resolved
with ease, with suitable objectives. Diatoms mounted dry are shown in
a manner far surpassing that by the usual arrangement of mirror,
particularly with large angle dry objectives.
Ottumwa, Ia.
WM. LIGHTON.
[Illustration: LIGHTON'S ILLUMINATOR.]
* * * * *
FOUCAULT'S PENDULUM EXPERIMENTS.
By RICHARD A. PROCTOR.
Science owes to M. Foucault the suggestion that the motions of a
pendulum so suspended as to be free to swing in any vertical plane
might be made to give ocular demonstration of the earth's rotation. The
principle of proof may be easily exhibited, though, like nearly all of
the evidences of the earth's rotation, the complete theory of the
matter can only be mastered by the aid of mathematical researches of
considerable complexity. Suppose A B (Fig. 1) to be a straight rod in a
horizontal position bearing the free pendulum C D suspended in some such
manner as is indicated at C; and suppose the pendulum to be set swinging
in the direction of the length of the rod A B, so that the bob D remains
throughout the oscillations vertically under the rod A B. Now, if A B be
shifted in the manner indicated by the arrows, its horizontality being
preserved, it will be found that the pendulum does not partake in this
motion. Thus, if the direction of A B was north and south at first, so
that the pendulum was set swinging in a north and south direction, it
will be found that, the pendulum will still swing in that direction,
even though the rod be made to take up an east and west position.
[Illustration: Fig. 1.]
Nor will it matter if we suppose B (say) fixed and the rod shifted by
moving the end A horizontally round B. Further, as this is true whatever
the length of the rod, it is clear that the same fixity of the plane
of swing will be observed if the rod be shifted horizontally as though
forming part of a radial line from a point E in its length. In these
cases the plane of the pendulum's swing will indeed be shifted _bodily_,
but the direction of swing will still continue to be from north to
south.
Now, let P O P' represent the polar axis of the earth; a b a horizontal
rod at the pole bearing a pendulum, as in Fig. 1. It is clear that if
the earth is rotating about P O P' in the direction shown by the arrow,
the rod a b is being shifted round, precisely as in the case first
considered. The swinging pendulum below it will not partake in its
motion; and thus, through whatever arc the earth rotates from west to
east, through the same arc will the plane of swing of the pendulum
appear to travel from east to west under a b.
But we cannot set up a pendulum to swing at the pole of the earth. Let
us inquire, then, whether the experiment ought to have similar results
if carried out elsewhere.
Suppose A B to be our pendulum-bearing rod, placed (for convenience of
description merely) in a north and south position. Then it is clear that
A B produced meets the polar axis produced (in E, suppose), and when,
owing to the earth's rotation, the rod has been carried to the position
A' B', it still passes through the point E. Hence it has shifted through
the angle A E A', a motion which corresponds to the case of the motion
of A B (in Fig. 1) about the point E,[1] and the plane of the pendulum's
swing will therefore show a displacement equal to the angle A E A'. It
will be at once seen that for a given arc of rotation the displacement
is smaller in this case than in the former, since the angle A E A' is
obviously less than the angle A K A'.[2] In our latitude a free pendulum
should seem to shift through one degree in about five minutes.
[Footnote 1: In reality A E moves to the position A' E over the surface
of a cone having E P' as axis, and E as vertex; but for any small part
of its motion, the effect is the same as though it traveled in a plane
through E, touching this cone; and the sum of the effects should clearly
be proportioned to the sum of the angular displacements.]
[Footnote 2: In fact, the former angle is less than the latter, in the
same proportion that A K is less than A E, or in the proportion of the
sine of the angle A E P, which is obviously the same as the sine of the
latitude.]
It is obvious that a great deal depends on the mode of suspension. What
is needed is that the pendulum should be as little affected as possible
by its connection with the rotating earth. It will surprise many,
perhaps, to learn that in Foucault's original mode of suspension the
upper end of the wire bearing the pendulum bob was fastened to a metal
plate by means of a screw. It might be supposed that the torsion of
the wire would appreciably affect the result. In reality, however, the
torsion was very small.
[Illustration: Fig. 2.]
Still, other modes of suspension are obviously suggested by the
requirements of the problem. Hansen made use of the mode of suspension
exhibited in Fig. 3. Mr. Worms, in a series of experiments carried out
at King's College, London, adopted a somewhat similar arrangement, but
in place of the hemispherical segment he employed a conoid, as shown in
Fig. 4, and a socket was provided in which the conoid could work freely.
From some experiments I made myself a score of years ago, I am inclined
to prefer a plane surface for the conoid to work upon. Care must be
taken that the first swing of the pendulum may take place truly in one
plane. The mode of liberation is also a matter of importance.
[Illustration: Fig.3.]
Many interesting experiments have been made upon the motions of a
free pendulum, regarded as a proof of the earth's rotation, and when
carefully conducted, the experiments have never failed to afford the
most satisfactory results. Space, however, will only permit me to dwell
on a single series of experiments. I select those made by Mr. Worms in
the Hall of King's College, London, in the year 1859:
"The bob was a truly turned ball of brass weighing 40 lb.; the
suspending medium was a thick steel wire; the length of the pendulum was
17 feet 9 inches. The amplitude of the first oscillation was 6 deg. 42', and
during the time of the experiment--about half an hour--the arcs were
not much diminished. As I had to demonstrate to a large number of
spectators, I encountered considerable difficulty," says Mr. Worms, "in
rendering the small deviations of the plane of oscillation visible to
all. I accomplished it in three different ways." These he proceeds
to describe. He had first a set of small cones set up, which were
successively knocked down as the change in the plane of the pendulum
slowly brought the pointer under the bob to bear on cone after cone.
Secondly, a small cannon was so placed that the first touch of the
pendulum pointer against a platinum wire across the touch-hole completed
a galvanic circuit, and so fired the cannon. Lastly, a candle was placed
so as to throw the shadow of the pendulum bob upon a ground-glass
screen, and so to exhibit the gradual change of the plane of swing.
The results accorded most satisfactorily with the deductions from the
theory of the earth's rotation.
[Illustration: Fig.4.]
* * * * *
A NEW LUNARIAN.
By Prof. C. W. MACCORD, Sc.D.
The construction of apparatus for illustrating the motions of the
heavenly bodies has often occupied the attention of both mathematicians
and mechanicians, who have produced many very ingenious, and in some
cases very complicated, combinations. These may be divided into two
classes; the object of the first being to represent _exactly_ what
occurs--to reproduce the precise movements of the various bodies
represented in their true proportions and relations to each other, in
respect to distances, magnitudes, times, and phases. When the absolute
complexity of the movements of the bodies composing the solar system
is considered, it is not so much a matter of wonder that a planetarium
which shall thus imitate them is a very delicate and complicated machine
as that it should lie within the limits of human ingenuity.
In the second class, the object is to show the nature and the causes
of specific phenomena, without regard to others perhaps, and without
necessarily paying attention to exact proportions of distances and
dimensions. Indeed, it is often the case that the illustration is made
clearer by exaggerating some of these and reducing others; thus, for
example, the causes of the variation in the lengths of the days and
nights, and of the changes in the seasons, can be exhibited to much
better advantage by an apparatus in which the diameter of the sun and
its distance from the earth are enormously reduced than they possibly
could be were they of their proper proportionate magnitudes; nor is the
presence of any other planet, or the attendance of a satellite, at all
necessary or even desirable for the purpose named.
It is apparent that machines of this class can be made much more simple
than those of the first, while at the same time it may safely be
asserted that for educational purposes they are far more useful.
In both classes, the action involves the use of some sort of epicyclic
train, since the motions to be explained are both orbital and axial. The
planetary body is carried round by a train-arm, and its rotation about
its axis is usually given it by a train of gearing, the inner or
central wheel of which is stationary, being fastened to the fixed frame
supporting the whole.
[Illustration: AN IMPROVED LUNARIAN.]
The lunarian which we herewith present belongs to the second of the
classes above named; in its construction an attempt has been made to
show by as simple means and in as clear a manner as possible the nature
of the following phenomena, viz.:
1. Apogee and perigee.
2. The moon's phases.
3. The rotation on her axis, by reason of which she always presents
nearly the same face to the earth.
4. The inclination of her axis to the plane of her orbit, and her
consequent libration in latitude.
5. Her varying angular velocity, and consequent libration in longitude.
The mechanism consists of a train-arm, T, which turns upon the vertical
pivot, P, fixed in the stand. In this arm, T, are the bearings of two
cranks, B and C. equal in length to each other and to a third crank, A,
which is stationary, being fixed to the pivot, P, by a pin, p. To the
crank-pin of A is secured a reverted arm, A', which supports the earth,
E, and keeps it also stationary. The three cranks are connected by the
rod, R, like the parallel rod of a locomotive: to which is fastened by a
steady-pin, o, the bevel wheel, D, concentric with the crank-pin, b. The
head of this crank-pin is first made spherical, then faced off at an
angle with the axis of b, and in the sloping face is firmly fixed the
long screw, S, forming the support for the moon, M, which is caused
to rotate about the axis of S, by means of the wheel, F, equal to
and engaging with D. The upper end of S projects slightly through a
perforation in the moon, and to it the hemispherical black shell or cap,
G, is fixed by the screw, K; this cap represents the unilluminated part
of the moon, and since G, s, b, and B, are in effect but one piece, the
cap moves precisely as the crank does.
Now as the train-arm, T, is carried round, the cranks, B and C, will
turn in their bearings; but by their connection with A, they are
compelled to remain always parallel to themselves, and thus the axis of
the moon receives a motion of translation. But since during this action
the wheel D turns relatively to the pin b, the moon evidently rotates
about its axis with an angular velocity precisely equal to that of its
orbital motion.
The black shell however has the motion of translation only, and thus
exhibits the phases of the moon, on the supposition that the source
of light is infinitely remote and the rays come always in the same
direction, which is not strictly true, of course; but the reasons of the
varying appearance are as clearly shown as if it were absolutely exact.
The same may be said in regard to the phenomena of libration; the
inclination of the moon's axis to the plane of her orbit is really
small, but is purposely exaggerated in this apparatus in order to make
the results apparent; in the position represented, it is quite obvious
that an observer upon the earth can see a little past one pole, and
cannot quite see the other, as well as that this condition will be
reversed after half a revolution.
The action in reference to the phases is clearly shown in the small
diagram on the right. The one on the left illustrates the manner in
which the libration in longitude is made apparent. It will be noted that
the center of M is not directly over the axis of the bearing of the
crank, B, so that after half a revolution the moon will be farther from
the earth than she is here shown. Her orbit here is circular, whereas,
in fact, it is an ellipse; but the earth not being in the center, her
angular velocity in relation to the earth is variable, the result
of which is that, when she is near her quadrature, the actual force
presented to the earth is slightly different from that presented when in
conjunction or opposition.
Thus these various peculiarities of the motion of our satellite are
exhibited by comparatively simple means--the number of moving parts
being, it is believed, as small as it can be made; and the substitution
of a crank motion for the usual train of wheels, we think, is a new
device.
* * * * *
THE UPRIGHT ATTITUDE OF MANKIND.
Every one must have heard or have read of the supposed perfect
adaptation of the human frame to bipedal locomotion and to an upright
attitude, as well as the advantages which we gain by this erect
position. We are told, and with perfect truth, that in man the occipital
foramen--the aperture through which the brain is connected with the
spinal cord--is so placed that the head is nearly in equilibrium when he
stands upright. In other mammalia this aperture lies further back, and
takes a more oblique direction, so that the head is thrown forward,
and requires to be upheld partly by muscular effort and partly by the
ligamentum nuchae, popularly known in cattle as the "pax-wax."
Again, the relative lengths of the bones of the hinder extremities in
man form an obstacle to his walking on all-fours. If we keep the legs
straight we may touch the ground in front of our feet with the tips of
the fingers, but we cannot place the palms of the hands upon the ground
and use them to support any part of our weight in walking. Not a few
other points of a similar tendency have been so often enlarged upon, in
works of a teleological character, that there can be no need even to
specify them at present.
But till lately it has never been asked, "Is man's adaptation to
an upright posture perfect?" and "Is this posture attended with no
drawbacks?" These questions have been raised by Dr. S. V. Clevenger in a
lecture delivered before the Chicago University Club, on April 18, 1882,
and recently published in the _American Naturalist_. This lecture,
we may add, cost the speaker the chair of Comparative Anatomy and
Physiology at the Chicago University!
Dr. Clevenger first discusses the position of the valves in the veins.
The teleologists have long told us that the valves in the veins of
the arms and legs assist in the return of blood to the heart against
gravitation. But what earthly use has a man for valves in the
intercostal veins which carry blood almost horizontally backward to the
azygos veins? When recumbent, these valves are an actual obstacle to
the free flow of the blood. The inferior thyroid veins which drop their
blood into the innominate are obstructed by valves at their junction.
Two pairs of valves are situate in the external jugular, and another
pair in the internal jugular, but they do not prevent regurgitation of
blood upward.
An anomaly exists in the absence of valves from parts where they are
most needed, such as the venae cavae, the spinal, iliac, haemorrhoidal, and
portal veins.
But if we place man upon all-fours these anomalies disappear, and a law
is found regulating the presence or absence of valves, and, according to
Dr. Clevenger, it is applicable to all quadrupeds and to the so-called
Quadrumana. Veins flowing toward the back, i.e., against gravitation in
the all-fours posture--are fitted with valves; those flowing in
other directions are without. For the few exceptions a very feasible
explanation is given.
Valves in the haemorrhoidal veins would be useless to quadrupeds; but to
man, in his upright position, they would be very valuable. "To their
absence in man many a life has been and will be sacrificed, to say
nothing of the discomfort and distress occasioned by the engorgement
known as piles, which the presence of valves in their veins would
obviate."
A noticeable departure from the rule obtaining in the vascular system of
mammalia also occurs to the exposed situation of the femoral artery in
man. The arteries lie deeper than the veins, or are otherwise protected,
for the purpose--as a teleologist would say--of preventing serious loss
of blood from superficial cuts. Translating this view into evolutionary
language, it appears that only animals with deeply placed arteries can
survive and transmit their structural peculiarities to their offspring.
The ordinary abrasions to which all animals are exposed, not to mention
their onslaughts upon each other, would quickly kill off species with
superficially placed arteries. But when man assumed the upright posture
the femoral artery, which in the quadrupedal position is placed out of
reach on the inner part of the thigh, became exposed. Were not this
defect greatly compensated by man's ability to protect this part in ways
not open to brutes, he, too, might have become extinct. As it is, this
exposure of so large an artery is a fruitful cause of trouble and death.
We may here mention some other disadvantages of the upright position
which Dr. Clevenger has omitted. Foremost comes the liability to fall
due to an erect posture supported upon two feet only. Four-footed
animals in their natural haunts are little liable to fall; if one foot
slips or fails to find hold, the other three are available. If a fall
does occur on level ground, there is very little danger to any mammal
nearly approaching man in bulk and weight. Their vital parts, especially
the heart and the head, are ordinarily so near the ground that to them
the shock is comparatively slight. To human beings the effects of a
fall on smooth, level ground are often serious, or even deadly. We need
merely call to mind the case of the illustrious physicist whom we have
so recently and suddenly lost.
The upright attitude involves a further sourge of danger. In few parts
(if any) of the body is a blow more fatal than over what is popularly
called the "pit of the stomach." In the quadruped this part is little
exposed either to accidental or intentional injuries. In man it is quite
open to both. A blow, a kick, a fall among stones, etc., may thus easily
prove fatal.
Another point is the exposure and prominence of the generative organs,
which in most other animals are well protected. Leaving danger out of
the question, it may be asked whether we have not here the origin of
clothing? The assumption of the upright posture may have made primitive
man aware of his nakedness.
Returning to the illustrations furnished by Dr. Clevenger, we are
reminded that another disadvantage which occurs from the upright
position of man is his greater liability to inguinal hernia. In
quadrupeds the main weight of the abdominal viscera is supported by the
ribs and by strong pectoral and abdominal muscles. The weakest part of
the latter group of muscles is in the region of Poupart's ligament,
above the groin. Inguinal hernia is rare in other vertebrates because
this weak part is relieved by the pressure of the viscera. In man the
pelvis receives almost the entire load of the intestines, and hence Art
is called in to compensate the deficiencies of nature, and an immense
number of trusses have to be manufactured and used. It is calculated
that 20 per cent. of the human family suffer in this way. Strangulated
hernia frequently causes death. The liability to femoral hernia is in
like manner increased by the upright position.
Now, if man has always been erect from his creation--or, if that term be
disliked, from his origin--we have evidently nothing to hope from the
future in the way of an amendment of this and other defects. But if we
have sprung from a quadrupedal animal, and have by degrees adopted
an upright position, to which we are as yet imperfectly adapted, the
muscular tissues of the abdomen will doubtless in the lapse of ages
become strengthened to meet the demand made upon them, so that the
liability to rupture will decrease. In like manner the other defects
above enumerated may gradually be rendered less serious.
A most important point remains; the peritoneal ligaments of the uterus
fully subserve suspensory functions. The anterior, posterior, and
lateral ligaments are mainly concerned in preventing the gravid uterus,
in quadrupeds, from pitching too far forward toward the diaphragm. The
round ligaments are utterly unmeaning in the human female, but in the
lower animals they serve the same purpose as the other ligaments.
Prolapsus uteri, from the erect position and the absence of supports
adapted to the position, is thus rendered common, destroying the health
and happiness of multitudes.
As a simple deduction from mechanical laws, it would readily follow that
any animal or race of men which had for the longest time maintained an
erect position would have straighter abdomens, wider pelvic brims with
contracted pelvic outlets, and that the weight of the spinal column
would force the sacrum lower down. This, generally speaking, we find to
be the case. In quadrupeds the box-shaped pelvis, which admits of easy
parturition, is prevalent. Where the position of the animal is such as
to throw the weight of the viscera into the pelvis, the brim necessarily
widens, these weighty organs sink lower, and the beads of the
thigh-bones acting as fulcra permit the crest of the ilium to be
carried outward, while the lower part of the pelvis is at the same time
contracted.
In the innominate bones of a young child the box-shape exists, while its
prominent abdomen resembles that of the gorilla. The gibbon exhibits
this iliac expansion through the sitting posture which developed his
ischial callosities. Similarly iliac expansion occurs in the chimpanzee.
The megatherium had wide iliacal expansions due to its semi-erect
habits; but as its weight was in great part supported by the huge tail,
and as the fermora rested in acetabula placed far forward, the leverage
necessary to contract the lower portion of the pelvis was absent.
Prof. Weber, of Bonn, quoted in Karl Vogt's "Vorlesungen ueber den
Mensohen," distinguishes four chief forms of the pelvis in mankind--the
oval in Aryans, the round among the Red Indians, the square in the
Mongols, and the wedge-shaped in the Negro. Examining this question
mechanically it would seem that the longer a race had remained in
an upright position the lower is the sacrum, and the greater is the
tendency to approximate to the larger lateral diameter of the European
female. The front to back diameter of the ape's pelvis is usually
greater than the measurement from side to side. A similar condition
affords the cuneiform, from which it may be inferred that the erect
position in the Negro has not been maintained so long as in the Mongol,
whose pelvis has assumed the quadrilateral shape owing to persistence
of spinal axis weight for a greater time. This pressure has finally
culminated in forcing the sacrum of the European nearer the pubes, with
consequent lateral expansion and contraction of the diameter from
front to back. From the marsupials to the lemurs the box-shaped pelvis
remains. With the wedge-shape occasioned in the lowest human types there
occurs a further remarkable phenomenon in the increased size of the
foetal head accompanying the contraction of the pelvic outlet. While the
marsupial head is about one-sixth the size of the narrowest part of the
bony parturient canal, the moment we pass to erect animals the greater
relative increase is there seen in cranial size, with a coexisting
decrease in the area of the outlet. This altered condition of things
has caused the death of millions of otherwise perfectly healthy and
well-formed human mothers and children. The palaeontologist might tell us
if some such case of ischial approximation by natural mechanical causes
has not caused the probable extinction of whole genera of vertebrates.
"If we are to believe that for our original sin the pangs and labor
of childbirth were increased, and if we also believe in the
disproportionate contraction of the pelvic space being an efficient
cause of the same difficulties of parturition, the logical inference is
that man's original sin consisted in his getting upon his hind legs."
This subject is not without direct applications. Accoucheurs cause their
patients to assume what is called the knee-chest position, a prone one,
for the purpose of restoring the uterus to something near a natural
position. Brown-Sequard recommends, in myelitis, or spinal congestion,
drawing away the blood from the spine by placing the patient on his
abdomen or side, with hands and feet somewhat hanging down. The
liability to _spina bifida_ is greatest in the human infant, through
the stress thrown on the spine. The easy parturition in the lower human
races is due to the discrepancy between cranial and pelvic sizes not
having been as yet reached by those races. The Sandwich Island mother
has a difficult delivery only when her child is half white, and has
consequently a longer head than the unmixed native strain.
At present the world goes on in its blindness, apparently satisfied
that everything is all right because its exists, ignorant of the evil
consequences of apparently beneficial pecularities, vaunting man's
erectness and its advantages, while ignoring the disadvantages.
The observation that the lower the animal the more prolific (not
universally true!) would warrant the belief that the higher the animal
the more difficulties encompass its propagation and development. The
cranio-pelvic difficulty may perhaps settle the Malthusian question as
far as the higher races of men are concerned by their extinction.
[If the facts brought forward by Dr. Clevenger cannot be controverted,
they seem to prove that man must have originated by gradual development
from a four-footed being. Had he been created an erect, bipedal animal,
as we find him, his structure would have been not in partial, but in
perfect, adaptation to the conditions of that attitude. That some of the
peculiarities of his structure are better in harmony with a horizontal
than a vertical position of the spinal column, is perhaps the strongest
argument against the theory of direct creation and the radical _toto
coelo_ distinction between man and beast that has yet been advanced. We
cannot at the moment lay our hands upon any thorough and trustworthy
account of the valves in the veins of the sloth: as that animal spends
its life hanging, back downward, the structure of the veins would be
interesting in this connection.--ED. J. S.]--_Journal of Science_.
* * * * *
OUR ENEMIES, THE MICROBES.
We have seen the microbes, as our servants[1], often performing,
unbeknown to us, the work of purifying and regenerating the soil and
atmosphere. Let us now examine our enemies, for they are numerous.
Everywhere frequent--in the air, in the earth, in the water--they only
await an occasion to introduce themselves into our body in order to
engage in a contest for existence with the cells that make up our
tissues; and, often victorious, they cause death with fearful rapidity.
When we have named charbon, septicaemia, diphtheria, typhoid fever, pork
measles, etc., we shall have indicated the serious affections that
microbes are capable of engendering in the animal organism.
[Footnote 1: SUPPLEMENT, No. 446, page 7125.]
We call those diseases "parasitic" that are occasioned by the
introduction of a living organism into the bodies of animals. Although a
knowledge of such diseases is easy where it concerns parasites such as
acari and worms, it becomes very difficult when it is a question of
diseases that are caused by the Bacteriaceae. In fact, the germs of these
plants exist in the air in large quantities, as is shown by the analysis
of pure air by a sunbeam, and we are obliged to take minute precautions
to prevent then from invading organic substances. If, then, during an
autopsy of an individual or animal, a microscopic examination reveals
the presence of microbes, we cannot affirm that the latter were the
cause of the affection that it is desired to study, since they might
have introduced themselves during the manipulation, and by reason of
their rapid vegetation have invaded the tissues of the dead animal in
a very short time. The presumption exists, nevertheless, that when
the same form of bacteria is present in the same tissue with the same
affection, it is connected with the disease. This was what Davaine was
the first to show with regard to _Bacillus anthracis_, which causes
charbon. He, in 1850, having examined the blood of an animal that had
died of this disease, found therein amid the globules (Fig. 1), small,
immovable, very narrow rods of a length double that of the blood
corpuscles. It was not till 1863 that he suspected the active role of
these organisms in the charbon malady, and endeavored to demonstrate it
by experiments in inoculation. Is the presence of these little rods in
the blood of an animal that has died of charbon sufficient of itself to
demonstrate the parasitic nature of the affection? No; in order that
the demonstration shall be complete, the bacteria must be isolated,
cultivated in a state of purity in proper liquids, and then be used
to inoculate animals with. If the latter die with all the symptoms
of charbon, the demonstration will be complete. Davaine did, indeed,
perform some experiments in inoculation that were successful, but his
results were contradicted by the experiments of Messrs. Jaillard and
Leplat, and those of Mr. Bert concerning the toxic influence of oxygen
at high tension upon microbes. As Davaine was unable to explain the
contradiction between his results and those of Messrs. Jaillard, Leplat,
and Bert, minds were not as yet convinced, notwithstanding the support
that his ideas received from Mr. Koch's researches.
In 1877 Mr. Pasteur took up Davaine's experiments, and confirmed his
affirmations step by step by employing the method of culture that he had
used with such success in his studies upon fermentation. He isolated
Davaine's bacterium by cultivating it in a decoction of beer yeast that
had been previously sterilized (Fig. 2); and after from ten to twenty
cultures, he found that a portion of the liquid containing a few
bacteria, when used for inoculating a rabbit, quickly caused the latter
to die of charbon, while the same liquid, when filtered through plaster
or porcelain, became harmless.
Davaine's bacterium develops exclusively in the blood, and is never
found at any depth in the tissues. This is due to the fact that the
alga, having need of oxygen in order to live, borrows its flow from the
blood, and thus extracts from the globules that which they should have
carried to the tissue. The animal therefore dies asphyxiated. It is on
account of the absence of oxygen in the blood that the latter assumes
the blackish-brown color that characterizes the malady, and that has
given its name of _charbon_ (coal).
The parasitic nature of charbon was therefore absolutely demonstrated,
first, by the constant presence of _Bacillus anthracis_ in the blood of
anthracoid animals, and second, by the pure culture of the parasite and
the inoculation of animals with charbon by means of it.
Davaine began the demonstration in 1863, and Pasteur finished it in
1877. These facts are now incontestable; yet, to show how slowly truth
is propagated, even in these days of telegraphs and telephones, there
might have been read a few months ago, in an interesting article on
microbes, by Dr. Fol, a distinguished savant, the statement that charbon
and tuberculosis were discovered by Dr. Koch!
New parasitic affections, whose existence was suspected, were soon
discovered and scientifically demonstrated, such, for example, as
septicaemia, or the putrefaction which occurs in living animals, which in
ambulances causes so fearful havoc among the wounded, and which proceeds
from _Bacillus septicus_. This parasite exhibits itself under the form
of little articulated rods that live isolated from oxygen in the mass of
the tissues, and disorganize the latter in disengaging a large quantity
of putrid gas. Other parasites of this class are the _micrococcus_ of
chicken cholera (Fig. 3), the _micrococcus_ of hog measles, and the
_Spirochoete Obermeieri_ of recurrent fever, discovered by Obermeier
(Fig. 5).
Besides these, there are a certain number of maladies that seem as if
they must be due to the Bacteriaceae, although a demonstration of the
fact by the method of cultures and inoculation has not as yet been
attempted. Among such, we may cite typhoid fever, diphtheria, murrain,
tuberculosis (Fig. 4), malarial fever (Fig. 6), etc.
As may be seen, the list is already a long one, and it tends every day
to still further increase. All the progress that has been made in so
few years in our knowledge of contagious or epidemic diseases is due
exclusively to M. Pasteur and the scientific method that he introduced
through his remarkable labors on fermentation. Now that we know our most
formidable enemies, how shall we defend ourselves against them?
As we have seen, bacteria exist everywhere, mixed with the dust that
interferes with the transparency of the air and covers all objects; and
they are likewise found in water.
Under normal conditions, our body is closed to these organisms through
the epidermis and epithelium, and, as has been shown by Mr. Pasteur, no
bacteria are found in the blood and tissues of living animals. But let a
rupture or wound occur, and bacteria will enter the body, and, when once
the enemy is in place, it will be too late. One sole chance of safety
remains to us, and that is that in the warfare that it is raging against
our tissues the enemy may succumb. M. Pasteur has shown that the blood
corpsucles sometimes engage in the contest against bacterides and
come off victorious. In fact, chickens are proof against poisoning by
charbon, because, owing to the high temperature of their blood, the
bacterides are unable to extract oxygen from the corpuscles thereof.
But, if the chickens be chilled, the conditions are changed, and they
will die of charbon just as do cattle and sheep; but, as the result of
the contest cannot always be foreseen, it is necessary at any cost to
prevent bacterides from entering the body.
[Illustration: I. Bacteria of charbon (_Bacillus antracis_.) II. The
same cultivated in yeast. III. The _Micrococcus_ of chicken cholera. IV.
The _Bacillus_ of tuberculosis. V. The _Spirillun_ of recurrent fever.
VI. The _Bacillus_ of malaria.]
Under ordinary circumstances a severe hygiene will suffice to preserve
us; if a wound is received it should be washed with water mixed with
antiseptics, such as phenic acid, borax, or salicylic acid. If water is
impure, it must be boiled and then aerated before it is drunk. If the
air is the vehicle of the germs of the disease, it will have to be
filtered by means of a muslin curtain kept wet with a hygroscopic
solution, glycerine for example. Finally, when, after an epidemic,
contaminated apartments are to be occupied, the walls and floor and the
clothing must be washed with antiseptic solutions whose nature will vary
according to circumstances--steam charged with phenic acid, water mixed
with a millionth part of sulphuric acid, boric acid, ozone, chlorine,
etc.
These preventives only prove efficient on condition that they be used
persistently. Let our vigilance be lacking for an instant, and the enemy
will enter to work destruction, for it only requires a spore less than
a hundredth of a millimeter in diameter to produce the most serious
affections.
Fortunately, and it is again to Mr. Pasteur that we owe these wonderful
discoveries, the parasitic microbes themselves, which sow sickness and
death, may, through proper culture, become true vaccine viri that are
capable of preserving the organism against any future attack of the
disease that they were capable of producing; such vaccine matters have
been discovered for charbon, chicken cholera, the measles of swine, etc.
When the _micrococcus_ of chicken cholera (Fig. 3.) is cultivated, it
is seen that the activity of the microbe in cultures exposed to the air
gradually diminishes. While a drop of the liquid would, in twenty-four
hours, have killed all the chickens that were inoculated with it, its
effect after two, three, or four days considerably diminishes, and an
inoculation with it produces nothing more than a slight indisposition in
the animal, and one that is never followed by a serious accident. It is
then said that the virulence of the microbe is attenuated.
The air is the agent of this transformation that gradually renders the
bacteria benign, for in cultures made under the same circumstances as
the preceding, but with the absence of air, the activity of these algae
is preserved for days or weeks, and they will then cause death just as
surely as they would have done at the end of one day.
What is remarkable is that animals inoculated with the attenuated
_micrococcus_ become for a varying length of time refractory to the
action of the most formidable parasites of this kind. Mr. Pasteur has
discovered two such vaccine viri--one for chicken cholera and the other
for charbon. His results have not been accepted without a struggle, and
it required nothing less than public experiment in vaccination, both in
France and abroad, to convince the incredulous. There are still people
at the present time who assert that Mr. Pasteur's process of vaccination
has not a great practical range! And yet, here we have the results; more
than 400,000 animals have been vaccinated since 1881, and it has been
found that the mortality is ten times less in these than in those that
have not been vaccinated!
An impetus has now been given, and we can look to the future with
confidence, for, if our enemies are numerous, the use of a severe
hygiene and preventive vaccination will permit us to gradually free
humanity from the terrible scourges that sap the sources of fortune and
life.--_Science et Nature_.
* * * * *
THE WINE FLY.
At the last meeting of the New York Microscopical Society, a paper
was read by Dr. Samuel Lockwood, secretary of the New Jersey State
Microscopical Society. His subject was the Wine Fly, _Drosophila
ampelophila_. The paper was a contribution to the life-history of this
minute insect. He had given in part three years to its study, beginning
in September, 1881, when nothing whatever of its life-history seemed to
have been known. In October the flies attacked his Concords. He found
upon a grape which he was inspecting with a pocket-lens an extremely
small white egg; but lost it. The grapes when brought on the table were
infested by the flies, which proved to be the above mentioned species.
When driven from the grapes they would fly to the window, where he
captured two of them These were placed in a jar with a grape for food.
In two days he found one egg on the outer skin of the grape. The laying
was kept up for four or five days, until there were about thirty, some
on the outside of the grape and some at an opening where the two flies
had fed. The egg had a pair of curious suspenders near the end where
the mouth of the larva would develop. These suspenders were attached at
their ends to the grape, but where the egg was laid in the soft part of
the fruit the suspenders were spread out at the surface; thus the larva
would emerge clean from the shell. The egg was 0.5 mm. in length, and
about a fourth of that in width. The larva when grown was at least four
times as long as the egg. As the larva burrowed in the juices of the
fruit, two quite prominent breathing tubes at the posterior end were
kept in the air. Between these cardinal tubes were several teat-like
points, much smaller, but having a similar function.
The larvae appeared in five days after the eggs were laid. In about as
many more days the puparium state would be entered, and in about six
days more the fly or imago would appear. In ovipositing the suspensors
would leave the oviparous duct last. The paper claimed that the curious
shape of the egg compelled the female to oviposit slowly, as it took
time for the egg to assume its form; hence, the eggs were not laid in
strings or masses, but singly and at considerable intervals.
The flies are very hairy, especially the females. The neck and even the
eyes are very hirsute. The eyes are red, quite large and pretty, though
somewhat _outre_ under the microscope, for from between the little
lenses are projecting, straight, stiff hairs. As the insect is quite
active, it must be that this fringing of the tiny eyelets with hair does
not materially obscure its vision. When the minuteness of this singular
arrangement is considered, it is surely remarkable. This general
hairiness of the female especially, and that about the head, neck, and
forward part of the thorax, stands correlated to a beautiful structure
found only in the male, which has on the tarsus of each leg in the
forward pair what the lecturer called a sexual comb. It is a beautiful
comb of a very dark brown color, each comb having ten pointed and strong
teeth. In the nuptial embrace these combs are fixed in the hairy front
of the thorax of the female, thus becoming little grapnels.
The flies love any vegetable substance in fermentation, whether acetic
or vinous. Hence it will abound about cider mills, swarm on preserves in
the pantry, and in cellars or places where wine is being made or stored.
The paper showed the tendency of the glucose in the over-ripe grape
to the vinous ferment, and that the fly delighted in it. A singular
accident showed how they loved even the very high spirits. In making
some of the mounts shown to the society, Dr. Lockwood had left a bottle
of 90 per cent. alcohol uncorked over night. Next morning he was
astonished to find his alcohol of a beautiful amethystine color, and the
cork out. Inspection showed a number of these tiny creatures, which,
when filled with the purple juice of the grape, had smelt the alcohol
in the open bottle, and had gone in to drink. They had ignominiously
perished, and had given color to the liquid.--_Micro. Journal_.
* * * * *
[NATURE.]
THE "POTETOMETER," AN INSTRUMENT FOR MEASURING THE TRANSPIRATION OF
WATER BY PLANTS.
In view of the interest now attaching to recent advances in vegetable
physiology, it seems not unlikely that a description of the instrument
bearing the above name, lately published by Moll (_Archives
Neerlandaises_, t. xviii.), will serve as useful purpose. The apparatus
was designed to do away with certain sources of error in Sachs'
older form of the instrument, described in his "Experimental
Physiologie"--errors chiefly due to the continual alteration of pressure
during the progress of the experiment.
As shown in the diagram, the "potetometer" consists essentially of a
glass tube, a d, open at both ends, and blown out into a bulb near the
lower end; an aperture also exists on either side of the bulb at or
about its equator. The two ends of the main tube are governed by the
stopcocks, a and d, and the greater length of the tube is graduated. A
perforated caoutchouc stopper is fitted into one aparture of the bulb,
e, and the tube, g k, fits hermetically to the other. This latter tube
is dilated into a cup at h to receive the caoutchouc stopper, into which
the end of the shoot to be experimented upon is properly fixed.
The fixing of the shoot is effected by caoutchouc and wire or silk, as
shown at i, and must be performed so that the clean-cut end of the
shoot is exactly at the level of a tube passing through the perforated
stopper, e, of the bulb; this is easily managed, and is provided for by
the bending of the tube, g h. The tube, f, passing horizontally through
the caoutchouc stopper, e, is intended to admit bubbles of air, and so
equalize the pressure and at the same time afford a means of measuring
the rapidity of the absorption of water by the transpiring shoot. This
tube (see Fig. 2, f) is a short piece of capillary glass tubing, to
which is fixed a thin sheath of copper, b', which slides on it, and
supports a small plate of polished copper, a', in such a manner that the
latter can be held vertically at a small distance from the inner opening
of the tube, and so regulate the size of the bubble of air to be
directed upward into the graduated tube, a b.
[Illustration]
The apparatus is filled by placing the lower end of the main tube under
water, closing the tubes, f and i (with caoutchouc tubing and clips),
and opening the stopcocks, a and d. Water is then sucked in from a, and
the whole apparatus carefully filled. The cocks are then turned, and the
cut end of the shoot fixed into i, as stated; care must be taken that no
air remains under the cut end at i, and the end of the shoot must be at
the level, k l. This done, the tube, f, may then be opened.
The leaves of the shoot transpire water, which is replaced through the
stem at the cut end in i from the water in the apparatus. A bubble of
air passes through the tube, f, and at once ascends into the graduated
tube, a c. The descent of the water-level in this tube--which may
conveniently be graduated to measure cubic millimeters--enables the
experimenter at once to read off the amount of water employed in a given
time.
It is not necessary to dwell on obvious modifications of these
essentials, nor to speak of the slight difficulties of manipulation
(especially with the tube, f). Of course the apparatus might be mounted
in several ways; and excellent results for demonstration in class could
be obtained by arranging the whole on one of the pans of a sensitive
balance. H. MARSHALL WARD.
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