Scientific American Supplement, No. 460, October 25, 1884
by
Various
Part 2 out of 2
hydrogen), while the thermal diffusivities of gases, calculated according
to Clausius' and Maxwell's kinetic theory of gases, are 0.089 for carbonic
acid, 0.16 for common air of other gases of nearly the same density, and
1.12 for hydrogen (all, both material and thermal, being reckoned in square
centimeters per second).]
Rich as it is in practical results, the kinetic theory of gases, as
hitherto developed, stops absolutely short at the atom or molecule, and
gives not even a suggestion toward explaining the properties in virtue of
which the atoms or molecules mutually influence one another. For some
guidance toward a deeper and more comprehensive theory of matter, we may
look back with advantage to the end of last century and beginning of this
century, and find Rumford's conclusion regarding the heat generated in
boring a brass gun: "It appears to me to be extremely difficult, if not
quite impossible, to form any distinct idea of anything capable of being
excited and communicated in the manner the heat was excited and
communicated in these experiments, except it be MOTION;" and Davy's still
more suggestive statements: "The phenomena of repulsion are not dependent
on a peculiar elastic fluid for their existence." ... "Heat may be defined
as a peculiar motion, probably a vibration, of the corpuscles of bodies,
tending to separate them." ... "To distinguish this motion from others, and
to signify the causes of our sensations of heat, etc., the name _repulsive_
motion has been adopted." Here we have a most important idea. It would be
somewhat a bold figure of speech to say the earth and moon are kept apart
by a repulsive motion; and yet, after all, what is centrifugal force but a
repulsive motion, and may it not be that there is no such thing as
repulsion, and that it is solely by inertia that what seems to be repulsion
is produced? Two bodies fly together, and, accelerated by mutual
attraction, if they do not precisely hit one another, they cannot but
separate in virtue of the inertia of their masses. So, after dashing past
one another in sharply concave curves round their common center of gravity,
they fly asunder again. A careless onlooker might imagine they had repelled
one another, and might not notice the difference between what he actually
sees and what he would see if the two bodies had been projected with great
velocity toward one another, and either colliding and rebounding, or
repelling one another into sharply convex continuous curves, fly asunder
again.
Joule, Clausius, and Maxwell, and no doubt Daniel Bernoulli himself, and I
believe every one who has hitherto written or done anything very explicit
in the kinetic theory of gases, has taken the mutual action of molecules in
collision as repulsive. May it not after all be attractive? This idea has
never left my mind since I first read Davy's "Repulsive Motion," about
thirty-five years ago, and I never made anything of it, at all events have
not done so until to-day (June 16, 1884)--if this can be said to be making
anything of it--when, in endeavoring to prepare the present address, I
notice that Joule's and my own old experiments[1] on the thermal effect of
gases expanding from a high-pressure vessel through a porous plug, proves
the less dense gas to have greater intrinsic _potential_ energy than the
denser gas, if we assume the ordinary hypothesis regarding the temperature
of a gas, according to which two gases are of equal temperatures [2] when
the kinetic energies of their constituent molecules are of equal average
amounts per molecule.
[Footnote 1: Republished in Sir W. Thomson's "Mathematical and Physical
Papers," vol. i., article xlix., p. 381. ]
[Footnote 2: That this is a mere hypothesis has been scarcely remarked by
the founders themselves, nor by almost any writer on the kinetic theory of
gases. No one has yet examined the question, What is the condition as
regards average distribution of kinetic energy, which is ultimately
fulfilled by two portions of gaseous matter, separated by a thin elastic
septum which absolutely prevents interdiffusion of matter, while it allows
interchange of kinetic energy by collisions against itself? Indeed, I do
not know but, that the present is the very first statement which has ever
been published of this condition of the problem of equal temperatures
between two gaseous masses.]
Think of the thing thus. Imagine a great multitude of particles inclosed by
a boundary which may be pushed inward in any part all round at pleasure.
Now station an engineer corps of Maxwell's army of sorting demons all round
the inclosure, with orders to push in the boundary diligently everywhere,
when none of the besieged troops are near, and to do nothing when any of
them are seen approaching, and until after they have turned again inward.
The result will be that, with exactly the same sum of kinetic and potential
energies of the same inclosed multitude of particles, the throng has been
caused to be denser. Now Joule's and my own old experiments on the efflux
of air prove that if the crowd be common air, or oxygen, or nitrogen, or
carbonic acid, the temperature is a little higher in the denser than in the
rarer condition when the energies are the same. By the hypothesis, equality
of temperature between two different gases or two portions of the same gas
at different densities means equality of kinetic energies in the same
number of molecules of the two. From our observations proving the
temperature to be higher, it therefore follows that the potential energy is
smaller in the condensed crowd. This--always, however, under protest as to
the temperature hypothesis--proves some degree of attraction among the
molecules, but it does not prove ultimate attraction between two molecules
in collision, or at distances much less than the average mutual distance of
nearest neighbors in the multitude. The collisional force might be
repulsive, as generally supposed hitherto, and yet attraction might
predominate in the whole reckoning of difference between the intrinsic
potential energies of the more dense and less dense multitudes.
It is however remarkable that the explanation of the propagation of sound
through gases, and even of the positive fluid pressure of a gas against the
sides of the containing vessel, according to the kinetic theory of gases,
is quite independent of the question whether the ultimate collisional force
is attractive or repulsive. Of course it must be understood that, if it is
attractive, the particles must, be so small that they hardly ever
meet--they would have to be infinitely small to _never_ meet--that, in
fact, they meet so seldom, in comparison with the number of times their
courses--are turned through large angles by attraction, that the influence
of these surely attractive collisions is preponderant over that of the
comparatively very rare impacts from actual contact. Thus, after all, the
train of speculation suggested by Davy's "Repulsive Motion" does not allow
us to escape from the idea of true repulsion, does not do more than let us
say it is of no consequence, nor even say this with truth, because, if
there are impacts at all, the nature of the force during the impact and the
effects of the mutual impacts, however rare, cannot be evaded in any
attempt to realize a conception of the kinetic theory of gases. And in
fact, unless we are satisfied to imagine the atoms of a gas as mathematical
points endowed with inertia, and as, according to Boscovich, endowed with
forces of mutual, positive, and negative attraction, varying according to
some definite function of the distance, we cannot avoid the question of
impacts, and of vibrations and rotations of the molecules resulting from
impacts, and we must look distinctly on each molecule as being either a
little elastic solid or a configuration of motion in a continuous
all-pervading liquid. I do not myself see how we can ever permanently rest
anywhere short of this last view; but it would be a very pleasant temporary
resting-place on the way to it if we could, as it were, make a mechanical
model of a gas out of little pieces of round, perfectly elastic solid
matter, flying about through the space occupied by the gas, and colliding
with one another and against the sides of the containing vessel.
This is, in fact, all we have of the kinetic theory of gases up to the
present time, and this has done for us, in the hands of Clausius and
Maxwell, the great things which constitute our first step toward a
molecular theory of matter. Of course from it we should have to go on to
find an explanation of the elasticity and all the other properties of the
molecules themselves, a subject vastly more complex and difficult than the
gaseous properties, for the explanation of which we assume the elastic
molecule; but without any explanation of the properties of the molecule
itself, with merely the assumption that the molecule has the requisite
properties, we might rest happy for a while in the contemplation of the
kinetic theory of gases, and its explanation of the gaseous properties,
which is not only stupendously important as a step toward a more
thoroughgoing theory of matter, but is undoubtedly the expression of a
perfectly intelligible and definite set of facts in Nature.
But alas for our mechanical model consisting of the cloud of little elastic
solids flying about among one another. Though each particle have absolutely
perfect elasticity, the end must be pretty much the same as if it were but
imperfectly elastic. The average effect of repeated and repeated mutual
collisions must be to gradually convert all the translational energy into
energy of shriller and shriller vibrations of the molecule. It seems
certain that each collision must have something more of energy in
vibrations of very finely divided nodal parts than there was of energy in
such vibrations before the impact. The more minute this nodal subdivision,
the less must be the tendency to give up part of the vibrational energy
into the shape of translational energy in the course of a collision; and I
think it is rigorously demonstrable that the whole translational energy
must ultimately become transformed into vibrational energy of higher and
higher nodal subdivisions if each molecule is a continuous elastic solid.
Let us, then, leave the kinetic theory of gases for a time with this
difficulty unsolved, in the hope that we or others after us may return to
it, armed with more knowledge of the properties of matter, and with sharper
mathematical weapons to cut through the barrier which at present hides from
us any view of the molecule itself, and of the effects other than mere
change of translational motion which it experiences in collision.
To explain the elasticity of a gas was the primary object of the kinetic
theory of gases. This object is only attainable by the assumption of an
elasticity more complex in character, and more difficult of explanation,
than the elasticity of gases--the elasticity of a solid. Thus, even if the
fatal fault in the theory, to which I have alluded, did not exist, and if
we could be perfectly satisfied with the kinetic theory of gases founded on
the collisions of elastic solid molecules, there would still be beyond it a
grander theory which need not be considered a chimerical object of
scientific ambition--to explain the elasticity of solids. But we may be
stopped when we commence to look in the direction of such a theory with the
cynical question, What do you mean by explaining a property of matter? As
to being stopped by any such question, all I can say is that if engineering
were to be all and to end all physical science, we should perforce be
content with merely finding properties of matter by observation, and using
them for practical purposes. But I am sure very few, if any, engineers are
practically satisfied with so narrow a view of their noble profession. They
must and do patiently observe, and discover by observation, properties of
matter and results of material combinations. But deeper questions are
always present, and always fraught with interest to the true engineer, and
he will be the last to give weight to any other objection to any attempt to
see below the surface of things than the practical question, Is it likely
to prove wholly futile? But now, instead of imagining the question, What do
you mean by explaining a property of matter? to be put cynically, and
letting ourselves be irritated by it, suppose we give to the questioner
credit for being sympathetic, and condescend to try and answer his
question. We find it not very easy to do so. All the properties of matter
are so connected that we can scarcely imagine one _thoroughly explained_
without our seeing its relation to all the others, without in fact having
the explanation of all; and till we have this we cannot tell what we mean
by "explaining a property" or "explaining the properties" of matter. But
though this consummation may never be reached by man, the progress of
science may be, I believe will be, step by step toward it, on many
different roads converging toward it from all sides. The kinetic theory of
gases is, as I have said, a true step on one of the roads. On the very
distinct road of chemical science, St. Claire Deville arrived at his grand
theory of dissociation without the slightest aid from the kinetic theory of
gases. The fact that he worked it out solely from chemical observation and
experiment, and expounded it to the world without any hypothesis whatever,
and seemingly even without consciousness of the beautiful explanation it
has in the kinetic theory of gases, secured for it immediately an
independent solidity and importance as a chemical theory when he first
promulgated it, to which it might even by this time scarcely have attained
if it had first been suggested as a probability indicated by the kinetic
theory of gases, and been only afterward confirmed by observation. Now,
however, guided by the views which Clausius and Williamson have given us of
the continuous interchange of partners between the compound molecules
constituting chemical compounds in the gaseous state, we see in Deville's
theory of dissociation a point of contact of the most transcendent interest
between the chemical and physical lines of scientific progress.
To return to elasticity: if we could make out of matter devoid of
elasticity a combined system of relatively moving parts which, in virtue of
motion, has the essential characteristics of an elastic body, this would
surely be, if not positively a step in the kinetic theory of matter, at
least a fingerpost pointing a way which we may hope will lead to a kinetic
theory of matter. Now this, as I have already shown,[1] we can do in
several ways. In the case of the last of the communications referred to, of
which only the title has hitherto been published, I showed that, from the
mathematical investigation of a gyrostatically dominated combination
contained in the passage of Thomson and Tait's "Natural Philosophy"
referred to, it follows that any ideal system of material particles, acting
on one another mutually through massless connecting springs, may be
perfectly imitated in a model consisting of rigid links jointed together,
and having rapidly rotating fly wheels pivoted on some or on all of the
links. The imitation is not confined to cases of equilibrium. It holds also
for vibration produced by disturbing the system infinitesimally from a
position of stable equilibrium and leaving it to itself. Thus we may make a
gyrostatic system such that it is in equilibrium under the influence of
certain positive forces applied to different points of this system; all the
forces being precisely the same as, and the points of application similarly
situated to, those of the stable system with springs. Then, provided proper
masses (that is to say, proper amounts and distributions of inertia) be
attributed to the links, we may remove the external forces from each
system, and the consequent vibration of the points of application of the
forces will be identical. Or we may act upon the systems of material points
and springs with any given forces for any given time, and leave it to
itself, and do the same thing for the gyrostatic system; the consequent
motion will be the same in the two cases. If in the one case the springs
are made more and more stiff, and in the other case the angular velocities
of the fly wheels are made greater and greater, the periods of the
vibrational constituents of the motion will become shorter and shorter, and
the amplitudes smaller and smaller, and the motions will approach more and
more nearly those of two perfectly rigid groups of material points moving
through space and rotating according to the well known mode of rotation of
a rigid body having unequal moments of inertia about its three principal
axes. In one case the ideal nearly rigid connection between the particles
is produced by massless, exceedingly stiff springs; in the other case it is
produced by the exceedingly rapid rotation of the fly wheels in a system
which, when the fly wheels are deprived of their rotation, is perfectly
limp.
[Footnote 1: Paper on "Vortex Atoms," _Proc_. R.S.E. February. 1867:
abstract of a lecture before the Royal Institution of Great Britain, March
4, 1881, on "Elasticity Viewed as possibly a Mode of Motion"; Thomson and
Tait's "Natural Philosophy," second edition, part 1, Sec.Sec. 345 viii. to 345
xxxvii.; "On Oscillation and Waves in an Adynamic Gyrostatic System" (title
only), _Proc_. R.S.E. March, 1883.]
The drawings (Figs. 1 and 2) before you illustrate two such material
systems.[1] The directions of rotation of the fly-wheels in the gyrostatic
system (Fig. 2) are indicated by directional ellipses, which show in
perspective the direction of rotation of the fly-wheel of each gyrostat.
The gyrostatic system (Fig. 2) might have been constituted of two
gyrostatic members, but four are shown for symmetry. The inclosing circle
represents in each case in section an inclosing spherical shell to prevent
the interior from being seen. In the inside of one there are fly-wheels, in
the inside of the other a massless spring. The projecting hooked rods seem
as if they are connected by a spring in each case. If we hang any one of
the systems up by the hook on one of its projecting rods, and hang a weight
to the hook of the other projecting rod, the weight, when first put on,
will oscillate up and down, and will go on doing so for ever if the system
be absolutely unfrictional. If we check the vibration by hand, the weight
will hang down at rest, the pin drawn out to a certain degree; and the
distance drawn out will be simply proportional to the weight hung on, as in
an ordinary spring balance.
[Footnote 1: In Fig. 1 the two hooked rods seen projecting from the sphere
are connected by an elastic coach-spring. In Fig. 2 the hooked rods are
connected one to each of two opposite corners of a four-sided jointed
frame, each member of which carries a gyrostat so that the axis of rotation
of the fly-wheel is in the axis of the member of the frame which bears it.
Each of the hooked rods in Fig. 2 is connected to the framework through a
swivel joint, so that the whole gyrostatic framework may be rotated about
the axis of the hooked rods in order to annul the moment of momentum of the
framework about this axis due to rotation of the fly-wheels in the
gyrostat.]
[Illustration: FIG. 1]
[Illustration: FIG. 2]
Here, then, out of matter possessing rigidity, but absolutely devoid of
elasticity, we have made a perfect model of a spring in the form of a
spring balance. Connect millions of millions of particles by pairs of rods
such as these of this spring balance, and we have a group of particles
constituting an elastic solid; exactly fulfilling the mathematical ideal
worked out by Navier, Poisson, and Cauchy, and many other mathematicians,
who, following their example, have endeavored to found a theory of the
elasticity of solids on mutual attraction and repulsion between a group of
material particles. All that can possibly be done by this theory, with its
assumption of forces acting according to any assumed law of relation to
distance, is done by the gyrostatic system. But the gyrostatic system does,
besides, what the system of naturally acting material particles cannot
do--it constitutes an elastic solid which can have the Faraday
magneto-optic rotation of the plane of polarization of light; supposing the
application of our solid to be a model of the luminiferous ether for
illustrating the undulatory theory of light. The gyrostatic model spring
balance is arranged to have zero moment of momentum as a whole, and
therefore to contribute nothing to the Faraday rotation; with this
arrangement the model illustrates the luminiferous ether in a field
unaffected by magnetic force. But now let there be a different rotational
velocity imparted to the jointed square round the axis of the two
projecting hooked rods, such as to give a resultant moment of momentum
round any given line through the center of inertia of the system; and let
pairs of the hooked rods in the model thus altered, which is no longer a
model of a mere spring balance, be applied as connections between millions
of pairs of particles as before, with the lines of resultant moment of
momentum all similarly directed. We now have a model elastic solid which
will have the property that the direction of vibration in waves of
rectilinear vibrations propagated through it shall turn round the line of
propagation of the waves, just as Faraday's observation proves to be done
by the line of vibration of light in a dense medium between the poles of a
powerful magnet. The case of wave front perpendicular to the lines of
resultant moment of momentum (that is to say, the direction of propagation
being parallel to these lines) corresponds, in our mechanical model, to the
case of light traveling in the direction of the lines of force in a
magnetic field.
In these illustrations and models we have different portions of ideal rigid
matter acting upon one another, by normal pressure at mathematical points
of contact--of course no forces of friction are supposed. It is exceedingly
interesting to see how thus, with no other postulates than inertia,
rigidity, and mutual impenetrability, we can thoroughly model not only an
elastic solid, and any combination of elastic solids, but so complex and
recondite a phenomenon as the passage of polarized light through a magnetic
field. But now, with the view of ultimately discarding the postulate of
rigidity from all our materials, let us suppose some to be absolutely
destitute of rigidity, and to possess merely inertia and incompressibility,
and mutual impenetrability with reference to the still remaining rigid
matter. With these postulates we can produce a perfect model of mutual
action at a distance between solid particles, fulfilling the condition, so
keenly desired by Newton and Faraday, of being explained by continuous
action through an intervening medium. The law of the mutual force in our
model, however, is not the simple Newtonian law, but the much more complex
law of the mutual action between electro magnets--with this difference,
that in the hydro-kinetic model in every case the force is opposite in
direction to the corresponding force in the electro-magnetic analogue.
Imagine a solid bored through with a hole, and placed in our ideal perfect
liquid. For a moment let the hole be stopped by a diaphragm, and let an
impulsure pressure be applied for an instant uniformly over the whole
membrane, and then instantly let the membrane be dissolved into liquid.
This action originates a motion of the liquid relatively to the solid, of a
kind to which I have given the name of "irrotational circulation," which
remains absolutely constant however the solid be moved through the liquid.
Thus, at any time the actual motion of the liquid at any point in the
neighborhood of the solid will be the resultant of the motion it would have
in virtue of the circulation alone, were the solid at rest, and the motion
it would have in virtue of the motion of the solid itself, had there been
no circulation established through the aperture. It is interesting and
important to remark in passing that the whole kinetic energy of the liquid
is the sum of the kinetic energies which it would have in the two cases
separately. Now, imagine the whole liquid to be inclosed in an infinitely
large, rigid, containing vessel, and in the liquid, at an infinite distance
from any part of the containing vessel, let two perforated solids, with
irrotational circulation through each, be placed at rest near one another.
The resultant fluid motion due to the two circulations, will give rise to
fluid pressure on the two bodies, which, if unbalanced, will cause them to
move. The force systems--force-and-torques, or pairs of forces--required to
prevent them from moving will be mutual and opposite, and will be the same
as, but opposite in direction to, the mutual force systems required to hold
at rest two electromagnets fulfilling the following specification: The two
electro magnets are to be of the same shape and size as the two bodies, and
to be placed in the same relative positions, and to consist of infinitely
thin layers of electric currents in the surfaces of solids possessing
extreme diamagnetic quality--in other words, infinitely small permeability.
The distribution of electric current on each body may be any whatever which
fulfills the condition that the total current across any closed line drawn
on the surface once through the aperture is equal to 1/4 [pi] of the
circulation[1] through the aperture in the hydro-kinetic analogue.
[Footnote 1: The integral of tangential component velocity all round any
closed curve, passing once through the aperture, is defined as the
"cyclic-constant" or the "circulation" ("Vortex Motion," Sec. 60 (a), _Trans_.
R.S.E., April 29, 1867). It has the same value for all closed curves
passing just once through the aperture, and it remains constant through all
time, whether the solid body be in motion or at rest.]
It might be imagined that the action at a distance thus provided for by
fluid motion could serve as a foundation for a theory of the equilibrium,
and the vibrations, of elastic solids, and the transmission of waves like
those of light through an extended quasi-elastic solid medium. But
unfortunately for this idea the equilibrium is essentially unstable, both
in the case of magnets and, notwithstanding the fact that the forces are
oppositely directed, in the hydro-kinetic analogue also, when the several
movable bodies (two or any greater number) are so placed relatively as to
be in equilibrium. If, however, we connect the perforated bodies with
circulation through them in the hydro-kinetic system, by jointed rigid
connecting links, we may arrange for configurations of stable equilibrium.
Thus, without fly-wheels, but with fluid circulations through apertures, we
may make a model spring balance or a model luminiferous ether, either
without or with the rotational quality corresponding to that of the true
luminiferous ether in the magnetic fluid--in short, do all by the
perforated solids with circulations through them that we saw we could do by
means of linked gyrostats. But something that we cannot do by linked
gyrostats we can do by the perforated bodies with fluid circulation: we can
make a model gas. The mutual action at a distance, repulsive or attractive
according to the mutual aspect of the two bodies when passing within
collisional distance[1] of one another, suffices to produce the change of
direction of motion in collision, which essentially constitutes the
foundation of the kinetic theory of gases, and which, as we have seen
before, may as well be due to attraction as to repulsion, so far as we know
from any investigation hitherto made in this theory.
[Footnote 1: According to this view, there is no precise distance, or
definite condition respecting the distance, between two molecules, at which
apparently they come to be in collision, or when receding from one another
they cease to be in collision. It is convenient, however, in the kinetic
theory of gases, to adopt arbitrarily a precise definition of collision,
according to which two bodies or particles mutually acting at a distance
may be said to be in collision when their mutual action exceeds some
definite arbitrarily assigned limit, as, for example, when the radius of
curvature of the path of either body is less than a stated fraction (one
one-hundredth, for instance) of the distance between them.]
There remains, however, as we have seen before, the difficulty of providing
for the case of actual impacts between the solids, which must be done by
giving them massless spring buffers or, which amounts to the same thing,
attributing to them repulsive forces sufficiently powerful at very short
distances to absolutely prevent impacts between solid and solid; unless we
adopt the equally repugnant idea of infinitely small perforated solids,
with infinitely great fluid circulations through them. Were it not for this
fundamental difficulty, the hydro-kinetic model gas would be exceedingly
interesting; and, though we could scarcely adopt it as conceivably a true
representation of what gases really are, it might still have some
importance as a model configuration of solid and liquid matter, by which
without elasticity the elasticity of true gas might be represented.
But lastly, since the hydro-kinetic model gas with perforated solids and
fluid circulations through them fails because of the impacts between the
solids, let us annul the solids and leave the liquid performing
irrotational circulation round vacancy,[1] in the place of the solid cores
which we have hitherto supposed; or let us annul the rigidity of the solid
cores of the rings, and give them molecular rotation according to
Helmholtz's theory of vortex motion. For stability the molecular rotation
must be such as to give the same velocity at the boundary of the rotational
fluid core as that of the irrotationally circulating liquid in contact with
it, because, as I have proved, frictional slip between two portions of
liquid in contact is inconsistent with stability. There is a further
condition, upon which I cannot enter into detail just now, but which may be
understood in a general way when I say that it is a condition of either
uniform or of increasing molecular rotation from the surface inward,
analogous to the condition that the density of a liquid, resting for
example under the influence of gravity, must either be uniform or must be
greater below than above for stability of equilibrium. All that I have said
in favor of the model vortex gas composed of perforated solids with fluid
circulations through them holds without modification for the purely
hydro-kinetic model, composed of either Helmholtz cored vortex rings or of
coreless vortices, and we are now troubled with no such difficulty as that
of the impacts between solids. Whether, however, when the vortex theory of
gases is thoroughly worked out, it will or will not be found to fail in a
manner analogous to the failure which I have already pointed out in
connection with the kinetic theory of gases composed of little elastic
solid molecules, I cannot at present undertake to speak with certainty. It
seems to me most probable that the vortex theory cannot fail in any such
way, because all I have been able to find out hitherto regarding the
vibration of vortices,[2] whether cored or coreless, does not seem to imply
the liability of translational or impulsive energies of the individual
vortices becoming lost in energy of smaller and smaller vibrations.
[Footnote 1: Investigations respecting coreless vortices will be found in a
paper by the author, "Vibrations of a Columnar Vortex," _Proc_. R.S.E.,
March 1, 1880; and a paper by Hicks, recently read before the Royal
Society.]
[Footnote 2: See papers by the author "On Vortex Motion." _Trans_. R.S.E.
April, 1867, and "Vortex Statics," _Proc_. R.S.E. December, 1875; also a
paper by J.J. Thomson, B.A., "On the Vibrations of a Vortex Ring," _Trans_.
R.S. December, 1881, and his valuable book on "Vortex Motion."]
As a step toward kinetic theory of matter, it is certainly most interesting
to remark that in the quasi-elasticity, elasticity looking like that of an
India-rubber band, which we see in a vibrating smoke-ring launched from an
elliptic aperture, or in two smoke-rings which were circular, but which
have become deformed from circularity by mutual collision, we have in
reality a virtual elasticity in matter devoid of elasticity, and even
devoid of rigidity, the virtual elasticity being due to motion, and
generated by the generation of motion.
* * * * *
APPLICATION OF ELECTRICITY TO TRAMWAYS.
By M. HOLROYD SMITH.
Last year, when I had the pleasure of reading a paper before you on my new
system of electric tramways, I ventured to express the hope that before
twelve months had passed, "to be able to report progress," and I am happy
to say that notwithstanding the wearisome delay and time lost in fruitless
negotiations, and the hundred and one difficulties within and without that
have beset me, I am able to appear before you again and tell you of
advance.
[Illustration: FIG. 1]
Practical men know well that there is a wide difference between a model and
a full sized machine; and when I decided to construct a full sized tramcar
and lay out a full sized track, I found it necessary to make many
alterations of detail, my chief difficulty being so to design my work as to
facilitate construction and allow of compensation for that inaccuracy of
workmanship which I have come to regard as inevitable.
In order to satisfy the directors of a tramway company of the practical
nature of my system before disturbing their lines, I have laid, in a field
near the works of Messrs. Smith, Baker & Co., Manchester, a track 110 yards
long, 4 ft. 81/2 in. gauge, and I have constructed a full sized street
tramcar to run thereon. My negotiations being with a company in a town
where there are no steep gradients, and where the coefficient of friction
of ordinary wheels would be sufficient for all tractive purposes, I thought
it better to avoid the complication involved in employing a large central
wheel with a broad surface specially designed for hilly districts, and with
which I had mounted a gradient of one in sixteen.
[Illustration: FIG. 2]
But as the line in question was laid with all the curves unnecessarily
quick, even those in the "pass-bies," I thought it expedient to employ
differential gear, as illustrated at D, Fig. 1, which is a sketch plan
showing the mechanism employed. M is a Siemens electric motor running at
650 revolutions per minute; E is a combination of box gearing, frictional
clutch, and chain pinion, and from this pinion a steel chain passes around
the chain-wheel, H, which is free to revolve upon the axle, and carries
within it the differential pinion, gearing with the bevel-wheel, B squared, keyed
upon the sleeve of the loose tram-wheel, T squared, and with the bevel-wheel, B,
keyed upon the axle, to which the other tram-wheel, T, is attached. To the
other tram-wheels no gear is connected; one of them is fast to the axle,
and the other runs loose, but to them the brake is applied in the usual
manner.
The electric current from the collector passes, by means of a copper wire,
and a switch upon the dashboard of the car, and resistance coils placed
under the seats, to the motor, and from the motor by means of an adjustable
clip (illustrated in diagram, Fig. 2) to the axles, and by them through the
four wheels to the rails, which form the return circuit.
[Illustration: FIG. 3]
I have designed many modifications of the track, but it is, perhaps, best
at present to describe only that which I have in actual use, and it is
illustrated in diagram, Fig. 3, which is a sectional and perspective view
of the central channel. L is the surface of the road, and SS are the
sleepers, CC are the chairs which hold the angle iron, AA forming the
longitudinally slotted center rail and the electric lead, which consists of
two half-tubes of copper insulated from the chairs by the blocks, I, I. A
special brass clamp, free to slide upon the tube, is employed for this
purpose, and the same form of clamp serves to join the two ends of the
copper tubes together and to make electric contact. Two half-tubes instead
of one slotted tube have been employed, in order to leave a free passage
for dirt or wet to fall through the slot in the center rail to the drain
space, G. Between chair and chair hewn granite or artificial stone is
employed, formed, as shown in the drawing, to complete the surface of the
road and to form a continuous channel or drain. In order that this drain
may not become choked, at suitable intervals, in the length of the track,
sump holes are formed as illustrated in diagram, Fig. 4 These sump holes
have a well for the accumulation of mud, and are also connected with the
main street drain, so that water can freely pass away. The hand holes
afford facility for easily removing the dirt.
In a complete track these hand holes would occasionally be wider than shown
here, for the purpose of removing or fixing the collector, Fig. 5, which
consists of two sets of spirally fluted rollers free to revolve upon
spindles, which are held by knuckle-joints drawn together by spiral
springs; by this means the pressure of the rollers against the inside of
the tube is constantly maintained, and should any obstruction occur in the
tube the spiral flute causes it to revolve, thus automatically cleansing
the tubes.
[Illustration: FIG. 4]
The collector is provided with two steel plates, which pass through the
slit in the center rail; the lower ends of these plates are clamped by the
upper frame of the collector, insulating material being interposed, and the
upper ends are held in two iron cheeks. Between these steel plates
insulated copper strips are held, electrically connected with the collector
and with the adjustable clip mounted upon the iron cheeks; this clip holds
the terminal on the end of the wire (leading to the motor) firmly enough
for use, the cheeks being also provided with studs for the attachment of
leather straps hooked on to the framework of the car, one for the forward
and one for backward movement of the collector. These straps are strong
enough for the ordinary haulage of the collector, and for the removal of
pebbles and dirt that may get into the slit; but should any absolute block
occur then they break and the terminal is withdrawn from the clip; the
electric contact being thereby broken the car stops, the obstruction can
then be removed and the collector reconnected without damage and with
little delay.
[Illustration: FIG. 5]
In order to secure continuity of the center rail throughout the length of
the track, and still provide for the removal of the collector at frequent
intervals, the framework of the collector is so made that, by slackening
the side-bolts, the steel plates can be drawn upward and the collector
itself withdrawn sideways through the hand holes, one of the half-tubes
being removed for the purpose.
Fig. 6 illustrates another arrangement that I have constructed, both of
collector and method of collecting.
[Illustration: FIG. 6]
As before mentioned, the arrangement now described has been carried out in
a field near the works of Messrs. Smith, Baker & Co., Cornbrook Telegraph
Works, Manchester, and its working efficiency has been most satisfactory.
After a week of rain and during drenching showers the car ran with the same
speed and under the same control as when the ground was dry.
This I account for by the theory that when the rails are wet and the tubes
moist the better contact made compensates for the slight leakage that may
occur.
At the commencement of my paper I promised to confine myself to work done;
I therefore abstain from describing various modifications of detail for the
same purpose. But one method of supporting and insulating the conductor in
the channel may be suggested by an illustration of the plan I adopted for a
little pleasure line in the Winter Gardens, Blackpool.
[Illustration: FIG. 7.]
Fig. 7. There the track being exclusively for the electric railway, it was
not necessary to provide a center channel; the conductor has therefore been
placed in the center of the track, and consists of bar iron 11/4 in. by 1/2
in., and is held vertically by means of studs riveted into the side; these
studs pass through porcelain insulators, and by means of wooden clamps and
wedges are held in the iron chairs which rest upon the sleepers. The iron
conductors were placed vertically to facilitate bending round the sharp
curves which were unavoidable on this line.
The collector consists of two metal slippers held together by springs,
attached to the car by straps and electrically connected to the motor by
clips in the same manner as the one employed in Manchester.
I am glad to say that, notwithstanding the curves with a radius of 55 feet
and gradients of 1 in 57, this line is also a practical success.
* * * * *
FIRES IN LONDON AND NEW YORK.
When the chief of the London Fire Brigade visited the United States in
1882, he was, as is the general rule on the other side of the Atlantic,
"interviewed"--a custom, it may be remarked, which appears to be gaining
ground also in this country. The inferences drawn from these interviews
seem to be that the absence of large fires in London was chiefly due to the
superiority of our fire brigade, and that the greater frequency of
conflagrations in American cities, and particularly in New York, was due to
the inferiority of their fire departments. How unjust such a comparison
would be is shown in a paper presented by Mr. Edward B. Dorsey, a member
of the American Society of Civil Engineers, to that association, in which
the author discusses the comparative liability to and danger from
conflagrations in London and in American cities. He found from an
investigation which he conducted with much care during a visit to London
that it is undoubtedly true that large fires are much less frequent in the
metropolis than in American cities; but it is equally true that the
circumstances existing in London and New York are quite different. As it is
a well-known fact that the promptness, efficiency, and bravery of American
firemen cannot be surpassed, we gladly give prominence to the result of the
author's investigations into the true causes of the great liability of
American cities to large fires. In a highly interesting comparison the
writer has selected New York and London as typical cities, although his
observations will apply to most American and English towns, if, perhaps,
with not quite the same force. In the first place, the efforts of the
London Fire Brigade receive much aid from our peculiarly damp climate. From
the average of eleven years (1871-1881) of the meteorological observations
made at the Greenwich Observatory, it appears that in London it rains, on
the average, more than three days in the week, that the sun shines only
one-fourth of the time he is above the horizon, and that the atmosphere
only lacks 18 per cent. of complete saturation, and is cloudy seven-tenths
of the time. Moreover, the humidity of the atmosphere in London is very
uniform, varying but little in the different months. Under these
circumstances, wood will not be ignited very easily by sparks or by contact
with a weak flame. This is very different from the condition of wood in the
long, hot, dry seasons of the American continent. The average temperature
for the three winter months in London is 38.24 degrees Fahr.; in New York
it is 31.56 degrees, or 6.68 degrees lower. This lower range of temperature
must be the cause of many conflagrations, for, to make up for the
deficiency in the natural temperature, there must be in New York many more
and larger domestic fires. The following statistics, taken from the records
of the New York Fire Department, show this. In the three winter months of
1881, January, February, and December, there were 522 fire alarms in New
York, or an average per month of 174; in the remaining nine months 1,263,
or an average per month of 140. In the corresponding three winter months of
1882 there were 602 fire alarms, or an average per month of 201; in the
remaining nine months 1,401, or an average per month of 155. In round
numbers there were in 1881 one-fourth, and in 1882 one-third more fire
alarms in the three winter months than in the nine warmer months. We are
not aware that similar statistics have ever been compiled for London, and
are consequently unable to draw comparison; but, speaking from
recollection, fires appear to be more frequent also in London during the
winter months.
Another cause of the greater frequency of fires in New York and their more
destructive nature is the greater density of population in that city. The
London Metropolitan Police District covers 690 square miles, extending 12
to 15 miles in every direction from Charing Cross, and contained in 1881 a
population of 4,764,312; but what is generally known as London covers 122
square miles, containing, in 1881, 528,794 houses, and a population of
3,814,574, averaging 7.21 persons per house, 49 per acre, and 31,267 per
square mile. Now let us look at New York. South of Fortieth Street between
the Hudson and East Rivers, New York has an area of 3,905 acres, a fraction
over six square miles, exclusive of piers, and contained, according to the
census of 1880, a population of 813,076. This gives 208 persons per acre.
The census of 1880 reports the total number of dwellings in New York at
73,684; total population, 1,206,299; average per dwelling, 16.37. Selecting
for comparison an area about equal from the fifteen most densely populated
districts or parishes of London, of an aggregate area of 3,896 acres, and
with a total population of 746,305, we obtain 191.5 persons per acre. Thus
briefly New York averaged 208 persons per acre, and 16.37 per dwelling;
London, for the same area, 191.5 persons per acre, and 7.21 per house. But
this comparison is scarcely fair, as in London only the most populous and
poorest districts are included, corresponding to the entirely tenement
districts of New York, while in the latter city it includes the richest and
most fashionable sections, as well as the poorest. If tenement districts
were taken alone, the population would be found much more dense, and New
York proportionately much more densely populated. Taking four of the most
thickly populated of the London districts (East London, Strand, Old Street,
St. Luke's, St. Giles-in-the-Fields, and St. George, Bloomsbury), we find
on a total area of 792 acres a population of 197,285, or an average of 249
persons per acre. In four of the most densely populated wards of New York
(10th, 11th, 13th, and 17th), we have on an area of 735 acres a population
of 258,966, or 352 persons per acre. This is 40 per cent. higher than in
London, the districts being about the same size, each containing about
1-1/5 square miles. Apart from the greater crowding which takes place in
New York, and the different style of buildings, another very fertile cause
of the spreading of fires is the freer use of wood in their construction.
It is asserted that in New York there is more than double the quantity of
wood used in buildings per acre than in London. From a house census
undertaken in 1882 by the New York Fire Department, moreover, it appears
that there were 106,885 buildings including sheds, of which 28,798 houses
were built of wood or other inflammable materials, besides 3,803 wooden
sheds, giving a total of 32,601 wooden buildings.
We are not aware that there are any wooden houses left in London. There are
other minor causes which act as checks upon the spreading of fires in
London. London houses are mostly small in size, and fires are thus confined
to a limited space between brick walls. Their walls are generally low and
well braced, which enable the firemen to approach them without danger.
About 60 per cent. of London houses are less than 22 feet high from the
pavement to the eaves; more than half of the remainder are less than 40
feet high, very few being over 50 feet high. This, of course, excludes the
newer buildings in the City. St. James's Palace does not exceed 40 feet,
the Bank of England not over 30 feet in height; but these are exceptional
structures. Fireproof roofings and projecting party walls also retard the
spreading of conflagrations. The houses being comparatively low and small,
the firemen are enabled to throw water easily over them, and to reach their
roofs with short ladders. There is in London an almost universal absence of
wooden additions and outbuildings, and the New York ash barrel or box kept
in the house is also unknown. The local authorities in London keep a strict
watch over the manufacture or storage of combustible materials in populous
parts of the city. Although overhead telegraph wires are multiplying to an
alarming extent in London, their number is nothing to be compared to their
bewildering multitude in New York, where their presence is not only a
hinderance to the operations of the firemen, but a positive danger to their
lives. Finally--and this has already been partly dealt with in speaking of
the comparative density of population of the two cities--a look at the map
of London will show us how the River Thames and the numerous parks,
squares, private grounds, wide streets, as well as the railways running
into London, all act as effectual barriers to the extension of fires.
The recent great conflagrations in the city vividly illustrate to Londoners
what fire could do if their metropolis were built on the New York plan. The
City, however, as we have remarked, is an exceptional part of London, and,
taking the British metropolis as it is, with its hundreds of square miles
of suburbs, and contrasting its condition with that of New York, we are led
to adopt the opinion that London, with its excellent fire brigade, is safe
from a destructive conflagration. It was stated above, and it is repeated
here, that the fire brigade of New York is unsurpassed for promptness,
skill, and heroic intrepidity, but their task, by contrast, is a heavy one
in a city like New York, with its numerous wooden buildings, wooden or
asphalt roofs, buildings from four to ten stories high, with long unbraced
walls, weakened by many large windows, containing more than ten times the
timber an average London house does, and that very inflammable, owing to
the dry and hot American climate. But this is not all. In New York we find
the five and six story tenement houses with two or three families on each
floor, each with their private ash barrel or box kept handy in their rooms,
all striving to keep warm during the severe winters of North America. We
also find narrow streets and high buildings, with nothing to arrest the
extension of a fire except a few small parks, not even projecting or
effectual fire-walls between the several buildings. And to all this must be
added the perfect freedom with which the city authorities of New York allow
in its most populous portions large stables, timber yards, carpenters'
shops, and the manufacture and storage of inflammable materials. Personal
liberty could not be carried to a more dangerous extent. We ought to be
thankful that in such matters individual freedom is somewhat hampered in
our old-fashioned and quieter-going country.--_London Morning Post_.
* * * * *
THE LATEST KNOWLEDGE ABOUT GAPES.
The gape worm may be termed the _bete noir_ of the poultry-keeper--his
greatest enemy--whether he be farmer or fancier. It is true there are some
who declare that it is unknown in their poultry-yards--that they have never
been troubled with it at all. These are apt to lay it down, as I saw a
correspondent did in a recent number of the _Country Gentleman_, that the
cause is want of cleanliness or neglect in some way. But I can vouch that
that is not so. I have been in yards where everything was first-rate, where
the cleanliness was almost painfully complete, where no fault in the way of
neglect could be found, and yet the gapes were there; and on the other
hand, I have known places where every condition seemed favorable to the
development of such a disease, and there it was absent--this not in
isolated cases, but in many. No, we must look elsewhere for the cause.
Observations lead me to the belief that gapes are more than usually
troublesome during a wet spring or summer following a mild winter. This
would tend to show that the egg from which the worm (that is in itself the
disease) emerges is communicated from the ground, from the food eaten, or
the water drunk, in the first instance, but it is more than possible that
the insects themselves may pass from one fowl to another. All this we can
accept as a settled fact, and also any description of the way in which the
parasitic worms attach themselves to the throats of the birds, and cause
the peculiar gaping of the mouth which gives the name to the disease.
Many remedies have been suggested, and my object now is to communicate some
of the later ones--thus to give a variety of methods, so that in case of
the failure of one, another will be at hand ready to be tried. It is a
mistake always to pin the faith to one remedy, for the varying conditions
found in fowls compel a different treatment. The old plan of dislodging the
worms with a feather is well known, and need not be described again. But I
may mention that in this country some have found the use of an ointment,
first suggested by Mr. Lewis Wright, I believe, most valuable. This is made
of mercurial ointment, two parts; pure lard, two parts; flour of sulphur,
one part; crude petroleum, one part--and when mixed together is applied to
the heads of the chicks as soon as they are dry after hatching. Many have
testified that they have never found this to fail as a preventive, and if
the success is to be attributed to the ointment, it would seem as if the
insects are driven off by its presence, for the application to the heads
merely would not kill the eggs.
Some time ago Lord Walsingham offered, through the Entomological Society of
London, a prize for the best life history of the gapes disease, and this
has been won by the eminent French scientist M. Pierre Megnin, whose essay
has been published by the noble donor. His offer was in the interest of
pheasant breeders, but the benefit is not confined to that variety of game
alone, for it is equally applicable to all gallinaceous birds troubled with
this disease. The pamphlet in question is a very valuable work, and gives
very clearly the methods by which the parasite develops. But for our
purpose it will be sufficient to narrate what M. Megnin recommends for the
cure of it. These are various, as will be seen, and comprise the experience
of other inquirers as well as himself.
He states that Montague obtained great success by a combination of the
following methods: Removal from infested runs; a thorough change of food,
hemp seed and green vegetables figuring largely in the diet; and for
drinking, instead of plain water, an infusion of rue and garlic. And Megnin
himself mentions an instance of the value of garlic. In the years 1877 and
1878, the pheasant preserves of Fontainebleau were ravaged by gapes. The
disease was there arrested and totally cured, when a mixture, consisting of
yolks of eggs, boiled bullock's heart, stale bread crumbs, and leaves of
nettle, well mixed and pounded together with garlic, was given, in the
proportion of one clove to ten young pheasants. The birds were found to be
very fond of this mixture, but great care was taken to see that the
drinking vessels were properly cleaned out and refilled with clean, pure
water twice a day. This treatment has met with the same success in other
places, and if any of your readers are troubled with gapes and will try it,
I shall be pleased to see the results narrated in the columns of the
_Country Gentleman_. Garlic in this case is undoubtedly the active
ingredient, and as it is volatile, when taken into the stomach the breath
is charged with it, and in this way (for garlic is a powerful vermifuge)
the worms are destroyed.
Another remedy recommended by M. Megnin was the strong smelling vermifuge
assafoetida, known sometimes by the suggestive name of "devil's dung." It
has one of the most disgusting oders possible, and is not very pleasant to
be near. The assafoetida was mixed with an equal part of powdered yellow
gentian, and this was given to the extent of about 8 grains a day in the
food. As an assistance to the treatment, with the object of killing any
embryos in the drinking water, fifteen grains of salicylate of soda was
mixed with a pint and three-quarters of water. So successful was this, that
on M. De Rothschild's preserves at Rambouillet, where a few days before
gapes were so virulent that 1,200 pheasants were found dead every morning,
it succeeded in stopping the epidemic in a few days. But to complete the
matter, M. Megnin adds that it is always advisable to disinfect the soil of
preserves. For this purpose, the best means of destroying any eggs or
embryos it may contain is to water the ground with a solution of sulphuric
acid, in the proportion of a pennyweight to three pints of water, and also
birds that die of the disease should be deeply buried in lime.
Fumigation with carbolic acid is an undoubted cure, but then it is a
dangerous one, and unless very great care is taken in killing the worms,
the bird is killed also. Thus many find this a risky method, and prefer
some other. Lime is found to be a valuable remedy. In some districts of
England, where lime-kilns abound, it is a common thing to take children
troubled with whooping-cough there. Standing in the smoke arising from the
kilns, they are compelled to breathe it. This dislodges the phlegm in the
throat, and they are enabled to get rid of it. Except near lime-kilns, this
cannot be done to chickens, but fine slaked lime can be used, either alone
or mixed with powdered sulphur, two parts of the former to one of the
latter. The air is charged with this fine powder, and the birds, breathing
it, cough, and thus get rid of the worms, which are stupefied by the lime,
and do not retain so firm a hold on the throat. An apparatus has recently
been introduced to spread this lime powder. It is in the form of an
air-fan, with a pointed nozzle, which is put just within the coop at night,
when the birds are all within. The powder is already in a compartment made
for it, and by the turning of a handle, it is driven through the nozzle,
and the air within the coop charged with it. There is no waste of powder,
nor any fear that it will not be properly distributed. Experienced pheasant
and poultry breeders state that by the use of this once a week, gapes are
effectually prevented. In this case, also, I shall be glad to learn the
result if tried.
STEPHEN BEALE.
H----, Eng., Aug. 1.
--_Country Gentleman_.
* * * * *
WOLPERT'S METHOD OF ESTIMATING THE AMOUNT OF CARBONIC ACID IN THE AIR.
There is a large number of processes and apparatus for estimating the
amount of carbonic acid in the air. Some of them, such as those of
Regnault, Reiset, the Montsouris observers (Fig. 1), and Brand, are
accurate analytical instruments, and consequently quite delicate, and not
easily manipulated by hygienists of middling experience. Others are less
complicated, and also less exact, but still require quite a troublesome
manipulation--such, for example, as the process of Pettenkofer, as modified
by Fodor, that of Hesse, etc.
[Illustration: APPARATUS FOR ESTIMATING THE CARBONIC ACID OF THE AIR.
FIG. 1.--Montsouris Apparatus. FIG. 2.--Smith's Minimetric Apparatus. FIG.
3.--Bertin-Sans Apparatus. FIG. 4.--Bubbling Glass. FIG. 5.--Pipette. FIG.
6.--Arrangement of the U-shaped Tube. FIG. 7.--Wolpert's Apparatus.]
Hygienists have for some years striven to obtain some very simple apparatus
(rather as an indicator than an analytical instrument) that should permit
it to be quickly ascertained whether the degree of impurity of a place was
incompatible with health, and in what proportion it was so. It is from such
efforts that have resulted the processes of Messrs. Smith. Lunge,
Bertin-Sans, and the apparatus of Prof. Wolpert (Fig. 7).
It is of the highest interest to ascertain the proportion of carbonic acid
in the air, and especially in that of inhabited places, since up to the
present this is the best means of finding out how much the air that we are
breathing is polluted, and whether there is sufficient ventilation or not.
Experiment has, in fact, demonstrated that carbonic acid increases in the
air of inhabited rooms in the same way as do those organic matters which
are difficult of direct estimation. Although a few ten-thousandths more of
carbonic acid in our air cannot of themselves endanger us, yet they have on
another hand a baneful significance, and, indeed, the majority of
hygienists will not tolerate more than six ten-millionths of this element
in the air of dwellings, and some of them not more than five
ten-millionths.
Carbonic acid readily betrays its presence through solutions of the
alkaline earths such as baryta and chalk, in which its passage produces an
insoluble carbonate, and consequently makes the liquid turbid. If, then,
one has prepared a solution of baryta or lime, of which a certain volume is
made turbid by the passage of a likewise known volume of CO_{2}, it will be
easy to ascertain how much CO_{2} a certain air contains, from the volume
of the latter that it will be necessary to pass through the basic solution
in order to obtain the amount of turbidity that has been taken as a
standard. The problem consists in determining the minimum of air required
to make the known solution turbid. Hence the name "minimetric estimation,"
that has been given to this process. Prof. Lescoeur has had the goodness to
construct for me a Smith's minimetric apparatus (Fig. 2) with the ingenious
improvements that have been made in it by Mr. Fischli, assistant to Prof.
Weil, of Zurich. I have employed it frequently, and I use it every year in
my lectures. I find it very practical, provided one has got accustomed to
using it. It is, at all events, of much simpler manipulation than that of
Bertin-Sans, although the accuracy of the latter may be greater (Figs. 3,
4, 5, and 6). But it certainly has more than one defect, and some of the
faults that have been found with it are quite serious. The worst of these
consists in the difficulty of catching the exact moment at which the
turbidity of the basic liquid is at the proper point for arresting the
operation. In addition to this capital defect, it is regrettable that it is
necessary to shake the flask that contains the solution after every
insufflation of air, and also that the play of the valves soon becomes
imperfect. Finally, Mr. Wolpert rightly sees one serious drawback to the
use of baryta in an apparatus that has to be employed in schools, among
children, and that is that this substance is poisonous. This gentleman
therefore replaces the solution of baryta by water saturated with lime,
which costs almost nothing, and the preparation of which is exceedingly
simple. Moreover, it is a harmless agent.
The apparatus consists of two parts. The first of these is a glass tube
closed at one end, and 12 cm. in length by 12 mm. in diameter. Its bottom
is of porcelain, and bears on its inner surface the date 1882 in black
characters. Above, and at the level that corresponds to a volume of three
cubic centimeters, there is a black line which serves as an invariable
datum point. A rubber bulb of twenty-eight cubic centimeters capacity is
fixed to a tube which reaches its bottom, and is flanged at the other
extremity (Fig. 7).
The operation is as follows:
The saturated, but limpid, solution of lime is poured into the first tube
up to the black mark, the tube of the air bulb is introduced into the lime
water in such a way that its orifice shall be in perfect contact with the
bottom of the other tube, and then, while the bulb is held between the fore
and middle fingers of the upturned hand, one presses slowly with the thumb
upon its bottom so as to expel all the air that it contains. This air
enters the lime-water bubble by bubble. After this the tube is removed from
the water, and the bulb is allowed to fill with air, and the same maneuver
is again gone through with. This is repeated until the figures 1882, looked
at from above, cease to be clearly visible, and disappear entirely after
the contents of the tube have been vigorously shaken.
The measures are such that the turbidity supervenes at once if the air in
the bulb contains twenty thousandths of CO_{2}. If it becomes necessary to
inject the contents of the bulb into the water twice, it is clear that the
proportion is only ten thousandths; and if it requires ten injections the
air contains ten times less CO_{2} than that having twenty thousandths, or
only two per cent. A table that accompanies the apparatus has been
constructed upon this basis, and does away with the necessity of making
calculations.
An air that contained ten thousandths of CO_{2}, or even five, would be
almost as deleterious, in my opinion, as one of two per cent. It is of no
account, then, to know the proportions intermediate to these round numbers.
Yet it is possible, if the case requires it, to obtain an indication
between two consecutive figures of the scale by means of another bulb whose
capacity is only half that of the preceding. Thus, two injections of the
large bulb, followed by one of the small, or two and a half injections,
correspond to a richness of 8 thousandths of CO_{2}; and 51/2 to 3.6
thousandths. This half-bulb serves likewise for another purpose. From the
moment that the large bulb makes the lime-water turbid with an air
containing two per cent. of CO_{2}, it is clear that the small one can
cause the same turbidity only with air twice richer in CO_{2}, _i.e._, of
four per cent.
This apparatus, although it makes no pretensions to extreme accuracy, is
capable of giving valuable information. The table that accompanies it is
arranged for a temperature of 17 deg. and a pressure of 740 mm. But different
meteorological conditions do not materially alter the results. Thus, with
10 deg. less it would require thirty-one injections instead of thirty, and
CO_{2} would be 0.64 per 1,000 instead of 0.66; and with 10 deg. more, thirty
injections instead of thirty one.
The apparatus is contained in a box that likewise holds a bottle of
lime-water sufficient for a dozen analyses, the table of proportions of
CO_{2}, and the apparatus for cleaning the tubes. The entire affair is
small enough to be carried in the pocket.--_J. Arnould, in Science et
Nature_.
* * * * *
[NATURE.]
THE VOYAGE OF THE VETTOR PISANI.
Knowing how much _Nature_ is read by all the naturalists of the world, I
send these few lines, which I hope will be of some interest.
The Italian R.N. corvette Vettor Pisani left Italy in April, 1882, for a
voyage round the world with the ordinary commission of a man-of-war. The
Minister of Marine, wishing to obtain scientific results, gave orders to
form, when possible, a marine zoological collection, and to carry on
surveying, deep-sea soundings, and abyssal thermometrical measurements. The
officers of the ship received their different scientific charges, and Prof.
Dohrn, director of the Zoological Station at Naples, gave to the writer
necessary instructions for collecting and preserving sea animals.
At the end of 1882 the Vettor Pisani visited the Straits of Magellan, the
Patagonian Channels, and Chonos and Chiloe islands; we surveyed the Darwin
Channel, and following Dr. Cuningham's work (who visited these places on
board H.M.S. Nassau), we made a numerous collection of sea animals by
dredging and fishing along the coasts.
While fishing for a big shark in the Gulf of Panama during the stay of our
ship in Taboga Island, one day in February, with a dead clam, we saw
several great sharks some miles from our anchorage. In a short time several
boats with natives went to sea, accompanied by two of the Vettor Pisani's
boats.
Having wounded one of these animals in the lateral part of the belly, we
held him with lines fixed to the spears; he then began to describe a very
narrow curve, and irritated by the cries of the people that were in the
boats, ran off with a moderate velocity. To the first boat, which held the
lines just mentioned, the other boats were fastened, and it was a rather
strange emotion to feel ourselves towed by the monster for more than three
hours with a velocity that proved to be two miles per hour. One of the
boats was filled with water. At last the animal was tired by the great loss
of blood, and the boats assembled to haul in the lines and tow the shark on
shore.
With much difficulty the nine boats towed the animal alongside the Vettor
Pisani to have him hoisted on board, but it was impossible on account of
his colossal dimensions. But as it was high water we went toward a sand
beach with the animal, and we had him safely stranded at night.
With much care were inspected the mouth, the nostrils, the ears, and all
the body, but no parasite was found. The eyes were taken out and prepared
for histological study. The set of teeth was all covered by a membrane that
surrounded internally the lips; the teeth are very little, and almost in a
rudimental state. The mouth, instead of opening in the inferior part of the
head, as in common sharks, was at the extremity of the head; the jaws
having the same bend.
Cutting the animal on one side of the backbone we met (1) a compact layer
of white fat 20 centimeters deep; (2) the cartilaginous ribs covered with
blood vessels; (3) a stratum of flabby, stringy, white muscle, 60
centimeters high, apparently in adipose degeneracy; (4) the stomach.
By each side of the backbone he had three chamferings, or flutings, that
were distinguished by inflected interstices. The color of the back was
brown with yellow spots that became close and small toward the head, so as
to be like marble spots. The length of the shark was 8.90 m. from the mouth
to the _pinna caudalis_ extremity, the greatest circumference 6.50 m., and
2.50 m. the main diameter (the outline of the two projections is made for
giving other dimensions).
The natives call the species _Tintoreva_, and the most aged of the village
had only once before fished such an animal, but smaller. While the animal
was on board we saw several _Remora_ about a foot long drop from his mouth;
it was proved that these fish lived fixed to the palate, and one of them
was pulled off and kept in the zoological collection of the ship.
The Vettor Pisani has up the present visited Gibraltar, Cape Verde Islands,
Pernambuco, Rio Janeiro, Monte Video, Valparaiso, many ports of Peru,
Guayaquil, Panama, Galapagos Islands, and all the collections were up to
this sent to the Zoological Station at Naples to be studied by the
naturalists. By this time the ship left Callao for Honolulu, Manila, Hong
Kong, and, as the Challenger had not crossed the Pacific Ocean in these
directions, we made several soundings and deep-sea thermometrical
measurements from Callao to Honolulu. Soundings are made with a steel wire
(Thompson system) and a sounding-rod invented by J. Palumbo, captain of the
ship. The thermometer employed is a Negretti and Zambra deep-sea
thermometer, improved by Captain Maguaghi (director of the Italian R.N.
Hydrographic Office).
With the thermometer wire has always been sent down a tow-net which opens
and closes automatically, also invented by Captain Palumbo. This tow-net
has brought up some little animals that I think are unknown.
G. CHIERCHIA.
Honolulu July 1.
The shark captured by the Vettor Pisani in the Gulf of Panama is _Rhinodon
typicus_, probably the most gigantic fish in existence. Mr. Swinburne Ward,
formerly commissioner of the Seychelles, has informed me that it attains to
a length of 50 feet or more, which statement was afterward confirmed by
Prof. E.P. Wright. Originally described by Sir A. Smith from a single
specimen which was killed in the neighborhood of Cape Town, this species
proved to be of not uncommon occurrence in the Seychelles Archipelago,
where it is known by the name of "Chagrin." Quite recently Mr. Haly
reported the capture of a specimen on the coast of Ceylon. Like other large
sharks (_Carcharodon rondeletii, Selache maxima_, etc.), Rhinodon has a
wide geographical range, and the fact of its occurrence on the Pacific
coast of America, previously indicated by two sources, appears now to be
fully established. T. Gill in 1865 described a large shark known in the
Gulf of California by the name of "Tiburon ballenas" or whale-shark, as a
distinct genus--_Micristodus punctatus_--which, in my opinion, is the same
fish. And finally, Prof. W. Nation examined in 1878 a specimen captured at
Callao. Of this specimen we possess in the British Museum a portion of the
dental plate. The teeth differ in no respect from those of a Seychelles
Chagrin; they are conical, sharply pointed, recurved, with the base of
attachment swollen. Making no more than due allowance for such variations
in the descriptions by different observers as are unavoidable in accounts
of huge creatures examined by some in a fresh, by others in a preserved,
state, we find the principal characteristics identical in all these
accounts, viz.: the form of the body, head, and snout, relative
measurements, position of mouth, nostrils, and eyes, dentition, peculiar
ridges on the side of the trunk and tail, coloration, etc. I have only to
add that this shark is stated to be of mild disposition and quite harmless.
Indeed, the minute size of its teeth has led to the belief in the
Seychelles that it is a herbivorous fish, which, however, is not probable.
ALBERT GUNTHER.
Natural History Museum, _July 30_.
* * * * *
THE GREELY ARCTIC EXPEDITION.
[Illustration: THE GREELY ARCTIC EXPEDITION.--THE FARTHEST POINT NORTH.]
Some account has been given of the American Meteorological Expedition,
commanded by Lieutenant, now Major, Greely, of the United States Army, in
the farthest north channels, beyond Smith Sound, that part of the Arctic
regions where the British Polar expedition, in May, 1876, penetrated to
within four hundred geographical miles of the North Pole. The American
expedition, in 1883, succeeded in getting four miles beyond, this being
effected by a sledge party traveling over the snow from Fort Conger, the
name they had given to their huts erected on the western shore near
Discovery Cove, in Lady Franklin Sound. The farthest point reached, on May
18, was in latitude 83 deg. 24 min. N.; longitude 40 deg. 46 min. W., on
the Greenland coast. The sledge party was commanded by Lieutenant Lockwood,
and the following particulars are supplied by Sergeant Brainerd, who
accompanied Lieutenant Lockwood on the expedition. During their sojourn in
the Arctic regions the men were allowed to grow the full beard, except
under the mouth, where it was clipped short. They wore knitted mittens, and
over these heavy seal-skin mittens were drawn, connected by a tanned
seal-skin string that passed over the neck, to hold them when the hands
were slipped out. Large tanned leather pockets were fastened outside the
jackets, and in very severe weather jerseys were sometimes worn over the
jackets for greater protection against the intense cold. On the sledge
journeys the dogs were harnessed in a fan-shaped group to the traces, and
were never run tandem. In traveling, the men were accustomed to hold on to
the back of the sledge, never going in front of the team, and often took
off their heavy overcoats and threw them on the load. When taking
observations with the sextant, Lieutenant Lockwood generally reclined on
the snow, while Sergeant Brainerd called time and made notes, as shown in
our illustration. When further progress northward was barred by open water,
and the party almost miraculously escaped drifting into the Polar sea,
Lieutenant Lockwood erected, at the highest point of latitude reached by
civilized man, a pyramidal-shaped cache of stones, six feet square at the
base, and eight or nine feet high. In a little chamber about a foot square
half-way to the apex, and extending to the center of the pile, he placed a
self-recording spirit thermometer, a small tin cylinder containing records
of the expedition, and then sealed up the aperture with a closely fitting
stone. The cache was surmounted with a small American flag made by Mrs.
Greely, but there were only thirteen stars, the number of the old
revolutionary flag. From the summit of Lockwood Island, the scene presented
in our illustration, 2,000 feet above the sea, Lieutenant Lockwood was
unable to make out any land to the north or the northwest. "The awful
panorama of the Arctic which their elevation spread out before them made a
profound impression upon the explorers. The exultation which was natural to
the achievement which they found they had accomplished was tempered by the
reflections inspired by the sublime desolation of that stern and silent
coast and the menace of its unbroken solitude. Beyond to the eastward was
the interminable defiance of the unexplored coast--black, cold, and
repellent. Below them lay the Arctic Ocean, buried beneath frozen chaos. No
words can describe the confusion of this sea of ice--the hopeless asperity
of it, the weariness of its torn and tortured surface. Only at the remote
horizon did distance and the fallen snow mitigate its roughness and soften
its outlines; and beyond it, in the yet unattainable recesses of the great
circle, they looked toward the Pole itself. It was a wonderful sight, never
to be forgotten, and in some degree a realization of the picture that
astronomers conjure to themselves when the moon is nearly full, and they
look down into the great plain which is called the Ocean of Storms, and
watch the shadows of sterile and airless peaks follow a slow procession
across its silver surface."--_Illustrated London News_.
* * * * *
THE NILE EXPEDITION.
[Illustration: WHALER GIG FOR THE NILE.]
As soon as the authorities had finally made up their minds to send a
flotilla of boats to Cairo for the relief of Khartoum, not a moment was
lost in issuing orders to the different shipbuilding contractors for the
completion, with the utmost dispatch, of the 400 "whaler-gigs" for service
on the Nile. They are light-looking boats, built of white pine, and weigh
each about 920 lb., that is without the gear, and are supposed to carry
four tons of provisions, ammunition, and camp appliances, the food being
sufficient for 100 days. The crew will number twelve men, soldiers and
sailors, the former rowing, while the latter (two) will attend the helm.
Each boat will be fitted with two lug sails, which can be worked reefed, so
as to permit an awning to be fitted underneath for protection to the men
from the sun. As is well known, the wind blows for two or three months
alternately up and down the Nile, and the authorities expect the flotilla
will have the advantage of a fair wind astern for four or five days at the
least. On approaching the Cataracts, the boats will be transported on
wooden rollers over the sand to the next level for relaunching.
* * * * *
THE PROPER TIME FOR CUTTING TIMBER.
_To the Editor of the Oregonian:_
Believing that any ideas relating to this matter will be of some interest
to your readers in this heavily-timbered region, I therefore propose giving
you my opinion and conclusions arrived at after having experimented upon
the cutting and use of timber for various purposes for a number of years
here upon the Pacific coast.
This, we are all well aware, is a very important question, and one very
difficult to answer, since it requires observation and experiment through a
course of many years to arrive at any definite conclusion; and it is a
question too upon which even at the present day there exists a great
difference of opinion among men who, being engaged in the lumber business,
are thereby the better qualified to form an opinion.
Many articles have been published in the various papers of the country upon
this question for the past thirty years, but in all cases an opinion only
has been given, which, at the present day, such is the advance and higher
development of the intellectual faculties of man, that a mere opinion upon
any question without sufficient and substantial reasons to back it is of
little value.
My object in writing this is not simply to give an opinion, but how and the
methods used by which I adopted such conclusions, as well also as the
reasons why timber is more durable and better when cut at a certain season
of the year than when cut at any other.
In the course of my investigations of this question for the past thirty
years, I have asked the opinion of a great many persons who have been
engaged in the lumber business in various States of the Union, from Maine
to Wisconsin, and they all agree upon one point, viz., that the winter time
is the proper time for cutting timber, although none has ever been able to
give a reason why, only the fact that such was the case, and therefore
drawing the inference that it was the proper time when timber should be
cut; and so it is, for one reason only, however, and that is the
convenience for handling or moving timber upon the snow and ice.
It was while engaged in the business of mining in the mountains of
California in early days, and having occasion to work often among timber,
in removing stumps, etc., it was while so engaged that I noticed one
peculiar fact, which was this--that the stumps of some trees which had been
cut but two or three years had decayed, while others of the same size and
variety of pine which had been cut the same year were as sound and firm as
when first cut. This seemed strange to me, and I found upon inquiry of old
lumbermen who had worked among timber all their lives, that it was strange
to them also, and they could offer no explanation; and it was the
investigation of this singular fact that led me to experiment further upon
the problem of cutting timber.
It was not, however, until many years after, and when engaged in clearing
land for farming purposes, that I made the discovery why some stumps should
decay sooner than others of the same size and variety, even when cut a few
months afterward.
I had occasion to clear several acres of land which was covered with a very
dense growth of young pines from two to six inches in diameter (this work
for certain reasons is usually done in the winter). The young trees, not
being suitable for fuel, are thrown into piles and burned upon the ground.
Such land, therefore, on account of the stumps is very difficult to plow,
as the stumps do not decay for three or four years, while most of the
larger ones remain sound even longer.
But, for the purpose of experimenting, I cleaned a few acres of ground in
the spring, cutting them in May and June. I trimmed the poles, leaving them
upon the ground, and when seasoned hauled them to the house for fuel, and
found that for cooking or heating purposes they were almost equal to oak;
and it was my practice for many years afterward to cut these young pines in
May or June for winter fuel.
I found also that the stumps, instead of remaining sound for any length of
time, decayed so quickly that they could all be plowed up the following
spring.
From which facts I draw these conclusions: that if in the cutting of timber
the main object is to preserve the stumps, cut your trees in the fall or
winter; but if the value of the timber is any consideration, cut your trees
in the spring after the sap has ascended the tree, but before any growth
has taken place or new wood has been formed.
I experimented for many years also in the cutting of timber for fencing,
fence posts, etc., and with the same results. Those which were cut in the
spring and set after being seasoned were the most durable, such timber
being much lighter, tougher, and in all respects better for all variety of
purposes.
Having given some little idea of the manner in which I experimented, and
the conclusions arrived at as to the proper time when timber should be cut,
I now propose to give what are, in my opinion, the reasons why timber cut
in early summer is much better, being lighter, tougher and more durable
than if cut at any other time. Therefore, in order to do this it is
necessary first to explain the nature and value of the sap and the growth
of a tree.
We find it to be the general opinion at present, as it perhaps has always
been among lumbermen and those who work among timber, that the sap of a
tree is an evil which must be avoided if possible, for it is this which
causes decay and destroys the life and good qualities of all wood when
allowed to remain in it for an unusual length of time, but that this is a
mistaken idea I will endeavor to show, not that the decay is due to the
sap, but to the time when the tree was felled.
We find by experiment in evaporating a quantity of sap of the pine, that it
is water holding in solution a substance of a gummy nature, being composed
of albumen and other elementary matters, which is deposited within the
pores of the wood from the new growth of the tree; that these substances in
solution, which constitute the sap, and which promote the growth of the
tree, should have a tendency to cause decay of the wood is an
impossibility. The injury results from the water only, and the improper
time of felling the tree.
Of the process in which the sap promotes the growth of the tree, the
scientist informs us that it is extracted from the soil, and flows up
through the pores of the wood of the tree, where it is deposited upon the
fiber, and by a peculiar process of nature the albumen forms new cells,
which in process of formation crowd and push out from the center, thus
constituting the growth of the tree in all directions from center to
circumference. Consequently this new growth of wood, being composed
principally of albumen, is of a soft, spongy nature, and under the proper
conditions will decay very rapidly, which can be easily demonstrated by
experiment.
Hence, we must infer that the proper time for felling the tree is when the
conditions are such that the rapid decay of a new growth of wood is
impossible; and this I have found by experiment to be in early summer,
after the sap has ascended the tree, but before any new growth of wood has
been formed. The new growth of the previous season is now well matured, has
become hard and firm, and will not decay. On the contrary, the tree being
cut when such new growth has not well matured, decay soon takes place, and
the value of the timber is destroyed. The effect of this cutting and use of
timber under the wrong conditions can be seen all around us. In the timbers
of the bridges, in the trestlework and ties of railroads and in the piling
of the wharves will be found portions showing rapid decay, while other
portions are yet firm and in sound condition.
Much more might be said in the explanation of this subject, but not wishing
to extend the subject to an improper length, I will close. I would,
however, say in conclusion that persons who have the opportunities and the
inclination can verify the truth of a portion, at least, of what I have
stated, in a simple manner and in a short time; for instance, by cutting
two or three young fir or spruce saplings, say about six inches in
diameter, mark them when cut, and also mark the stumps by driving pegs
marked to correspond with the trees. Continue this monthly for the space of
about one year, and note the difference in the wood, which should be left
out and exposed to the weather until seasoned.
C.W. HASKINS.
* * * * *
RAISING FERNS FROM SPORES.
[Illustration: 1, PAN; 2, BELL GLASS; 3, SMALL POTS AND LABELS.]
This plan, of which I give a sketch, has been in use by myself for many
years, and most successfully. I have at various times given it to growers,
but still I hear of difficulties. Procure a good sized bell-glass and an
earthenware pan without any holes for drainage. Prepare a number of small
pots, all filled for sowing, place them inside the pan, and fit the glass
over them, so that it takes all in easily. Take these filled small pots out
of the pan, place them on the ground, and well water them with boiling
water to destroy all animal and vegetable life, and allow them to get
perfectly cold; use a fine rose. Then taking each small pot separately, sow
the spores on the surface and label them; do this with the whole number,
and then place them in the pan under the bell-glass. This had better be
done in a room, so that nothing foreign can grow inside. Having arranged
the pots and placed the glass over them, and which should fit down upon the
pan with ease, take a clean sponge, and tearing it up pack the pieces round
the outside of the glass, and touching the inner side of the pan all round.
Water this with cold water, so that the sponge is saturated. Do this
whenever required, and always use water that has been boiled. At the end of
six weeks or so the prothallus will perhaps appear, certainly in a week or
two more; perhaps from unforeseen circumstances not for three months.
Slowly these will begin to show themselves as young ferns, and most
interesting it is to watch the results. As the ferns are gradually
increasing in size pass a small piece of slate under the edge of the
bell-glass to admit air, and do this by very careful degrees, allowing more
and more air to reach them. Never water overhead until the seedlings are
acclimated and have perfect form as ferns, and even then water at the edges
of the pots. In due time carefully prick out, and the task so interesting
to watch is performed.--_The Garden_.
* * * * *
THE LIFE HISTORY OF VAUCHERIA.
[Footnote: Read before the San Francisco Microscopical Society, August 13,
and furnished for publication in the _Press_.]
By A.H. BRECKENFELD.
Nearly a century ago, Vaucher, the celebrated Genevan botanist, described a
fresh water filamentous alga which he named _Ectosperma geminata_, with a
correctness that appears truly remarkable when the imperfect means of
observation at his command are taken into consideration. His pupil, De
Candolle, who afterward became so eminent a worker in the same field, when
preparing his "Flora of France," in 1805, proposed the name of _Vaucheria_
for the genus, in commemoration of the meritorious work of its first
investigator. On March 12, 1826, Unger made the first recorded observation
of the formation and liberation of the terminal or non-sexual spores of
this plant. Hassall, the able English botanist, made it the subject of
extended study while preparing his fine work entitled "A History of the
British Fresh Water Algae," published in 1845. He has given us a very
graphic description of the phenomenon first observed by Unger. In 1856
Pringsheim described the true sexual propagation by oospores, with such
minuteness and accuracy that our knowledge of the plant can scarcely be
said to have essentially increased since that time.
[Illustration: GROWTH OF THE ALGA, VAUCHERIA, UNDER THE MICROSCOPE.]
_Vaucheria_ has two or three rather doubtful marine species assigned to it
by Harvey, but the fresh water forms are by far the more numerous, and it
is to some of these I would call your attention for a few moments this
evening. The plant grows in densely interwoven tufts, these being of a
vivid green color, while the plant is in the actively vegetative condition,
changing to a duller tint as it advances to maturity. Its habitat (with the
exceptions above noted) is in freshwater--usually in ditches or slowly
running streams. I have found it at pretty much all seasons of the year, in
the stretch of boggy ground in the Presidio, bordering the road to Fort
Point. The filaments attain a length of several inches when fully
developed, and are of an average diameter of 1/250 (0.004) inch. They
branch but sparingly, or not at all, and are characterized by consisting of
a single long tube or cell, not divided by septa, as in the case of the
great majority of the filamentous algae. These tubular filaments are
composed of a nearly transparent cellulose wall, including an inner layer
thickly studded with bright green granules of chlorophyl. This inner layer
is ordinarily not noticeable, but it retracts from the outer envelope when
subjected to the action of certain reagents, or when immersed in a fluid
differing in density from water, and it then becomes distinctly visible, as
may be seen in the engraving (Fig. 1). The plant grows rapidly and is
endowed with much vitality, for it resists changes of temperature to a
remarkable degree. _Vaucheria_ affords a choice hunting ground to the
microscopist, for its tangled masses are the home of numberless infusoria,
rotifers, and the minuter crustacea, while the filaments more advanced in
age are usually thickly incrusted with diatoms. Here, too, is a favorite
haunt of the beautiful zoophytes, _Hydra vividis_ and _H. vulgaris_, whose
delicate tentacles may be seen gracefully waving in nearly every gathering.
REPRODUCTION IN VAUCHERIA.
After the plant has attained a certain stage in its growth, if it be
attentively watched, a marked change will be observed near the ends of the
filaments. The chlorophyl appears to assume a darker hue, and the granules
become more densely crowded. This appearance increases until the extremity
of the tube appears almost swollen. Soon the densely congregated granules
at the extreme end will be seen to separate from the endochrome of the
filament, a clear space sometimes, but not always, marking the point of
division. Here a septum or membrane appears, thus forming a cell whose
length is about three or four times its width, and whose walls completely
inclose the dark green mass of crowded granules (Fig. 1, b). These contents
are now gradually forming themselves into the spore or "gonidium," as
Carpenter calls it, in distinction from the true sexual spores, which he
terms "oospores." At the extreme end of the filament (which is obtusely
conical in shape) the chlorophyl grains retract from the old cellulose
wall, leaving a very evident clear space. In a less noticeable degree, this
is also the case in the other parts of the circumference of the cell, and,
apparently, the granular contents have secreted a separate envelope
entirely distinct from the parent filament. The grand climax is now rapidly
approaching. The contents of the cell near its base are now so densely
clustered as to appear nearly black (Fig. 1, c), while the upper half is of
a much lighter hue and the separate granules are there easily
distinguished, and, if very closely watched, show an almost imperceptible
motion. The old cellulose wall shows signs of great tension, its conical
extremity rounding out under the slowly increasing pressure from within.
Suddenly it gives way at the apex. At the same instant, the inclosed
gonidium (for it is now seen to be fully formed) acquires a rotary motion,
at first slow, but gradually increasing until it has gained considerable
velocity. Its upper portion is slowly twisted through the opening in the
apex of the parent wall, the granular contents of the lower end flowing
into the extruded portion in a manner reminding one of the flow of
protoplasm in a living amoeba. The old cell wall seems to offer
considerable resistance to the escape of the gonidium, for the latter,
which displays remarkable elasticity, is pinched nearly in two while
forcing its way through, assuming an hour glass shape when about half out.
The rapid rotation of the spore continues during the process of emerging,
and after about a minute it has fully freed itself (Fig 1, a). It
immediately assumes the form of an ellipse or oval, and darts off with
great speed, revolving on its major axis as it does so. Its contents are
nearly all massed in the posterior half, the comparatively clear portion
invariably pointing in advance. When it meets an obstacle, it partially
flattens itself against it, then turns aside and spins off in a new
direction. This erratic motion is continued for usually seven or eight
minutes. The longest duration I have yet observed was a little over nine
and one-half minutes. Hassall records a case where it continued for
nineteen minutes. The time, however, varies greatly, as in some cases the
motion ceases almost as soon as the spore is liberated, while in open
water, unretarded by the cover glass or other obstacles, its movements have
been seen to continue for over two hours.
The motile force is imparted to the gonidium by dense rows of waving cilia
with which it is completely surrounded. Owing to their rapid vibration, it
is almost impossible to distinguish them while the spore is in active
motion, but their effect is very plainly seen on adding colored pigment
particles to the water. By subjecting the cilia to the action of iodine,
their motion is arrested, they are stained brown, and become very plainly
visible.
After the gonidium comes gradually to a rest its cilia soon disappear, it
becomes perfectly globular in shape, the inclosed granules distribute
themselves evenly throughout its interior, and after a few hours it
germinates by throwing out one, two, or sometimes three tubular
prolongations, which become precisely like the parent filament (Fig 2).
Eminent English authorities have advanced the theory that the ciliated
gonidium of _Vaucheria_ is in reality a densely crowded aggregation of
biciliated zoospores, similar to those found in many other confervoid algae.
Although this has by no means been proved, yet I cannot help calling the
attention of the members of this society to a fact which I think strongly
bears out the said theory: While watching a gathering of _Vaucheria_ one
morning when the plant was in the gonidia-forming condition (which is
usually assumed a few hours after daybreak), I observed one filament, near
the end of which a septum had formed precisely as in the case of ordinary
filaments about to develop a spore. But, instead of the terminal cell being
filled with the usual densely crowded cluster of dark green granules
constituting the rapidly forming spore, it contained hundreds of actively
moving, nearly transparent zoospores, _and nothing else_. Not a single
chlorophyl granule was to be seen. It is also to be noted as a significant
fact, that the cellulose wall was _intact_ at the apex, instead of showing
the opening through which in ordinary cases the gonidium escapes. It would
seem to be a reasonable inference, I think, based upon the theory above
stated, that in this case the newly formed gonidium, unable to escape from
its prison by reason of the abnormal strength of the cell wall, became
after a while resolved into its component zoospores.
WONDERS OF REPRODUCTION.
I very much regret that my descriptive powers are not equal to conveying a
sufficient idea of the intensely absorbing interest possessed by this
wonderful process of spore formation. I shall never forget the bright sunny
morning when for the first time I witnessed the entire process under the
microscope, and for over four hours scarcely moved my eyes from the tube.
To a thoughtful observer I doubt if there is anything in the whole range of
microscopy to exceed this phenomenon in point of startling interest. No
wonder that its first observer published his researches under the caption
of "The Plant at the Moment of becoming an Animal."
FORMATION OF OTHER SPORES.
The process of spore formation just described, it will be seen, is entirely
non-sexual, being simply a vegetative process, analogous to the budding of
higher plants, and the fission of some of the lower plants and animals.
_Vaucheria_ has, however, a second and far higher mode of reproduction,
viz., by means of fertilized cells, the true oospores, which, lying dormant
as resting spores during the winter, are endowed with new life by the
rejuvenating influences of spring. Their formation may be briefly described
as follows:
When _Vaucheria_ has reached the proper stage in its life cycle, slight
swellings appear here and there on the sides of the filament. Each of these
slowly develops into a shape resembling a strongly curved horn. This
becomes the organ termed the _antheridium_, from its analogy in function to
the anther of flowering plants. While this is in process of growth,
peculiar oval capsules or sporangia (usually 2 to 5 in number) are formed
in close proximity to the antheridium. In some species both these organs
are sessile on the main filament, in others they appear on a short pedicel
(Figs. 3 and 4). The upper part of the antheridium becomes separated from
the parent stem by a septum, and its contents are converted into ciliated
motile antherozoids. The adjacent sporangia also become cut off by septa,
and the investing membrane, when mature, opens: it a beak-like
prolongation, thus permitting the inclosed densely congregated green
granules to be penetrated by the antherozoids which swarm from the
antheridium at the same time. After being thus fertilized the contents of
the sporangium acquire a peculiar oily appearance, of a beautiful emerald
color, an exceedingly tough but transparent envelope is secreted, and thus
is constituted the fully developed oospore, the beginner of a new
generation of the plant. After the production of this oospore the parent
filament gradually loses its vitality and slowly decays.
The spore being thus liberated, sinks to the bottom. Its brilliant hue has
faded and changed to a reddish brown, but after a rest of about three
months (according to Pringsheim, who seems to be the only one who has ever
followed the process of oospore formation entirely through), the spore
suddenly assumes its original vivid hue and germinates into a young
_Vaucheria_.
CHARM OF MICROSCOPICAL STUDY.
This concludes the account of my very imperfect attempt to trace the life
history of a lowly plant. Its study has been to me a source of ever
increasing pleasure, and has again demonstrated how our favorite instrument
reveals phenomena of most absorbing interest in directions where the
unaided eye finds but little promise. In walking along the banks of the
little stream, where, half concealed by more pretentious plants, our humble
_Vaucheria_ grows, the average passer by, if he notices it at all, sees but
a tangled tuft of dark green "scum." Yet, when this is examined under the
magic tube, a crystal cylinder, closely set with sparkling emeralds, is
revealed. And although so transparent, so apparently simple in structure
that it does not seem possible for even the finest details to escape our
search, yet almost as we watch it mystic changes appear. We see the bright
green granules, impelled by an unseen force, separate and rearrange
themselves in new formations. Strange outgrowths from the parent filament
appear. The strange power we call "life," doubly mysterious when manifested
in an organism so simple as this, so open to our search, seems to challenge
us to discover its secret, and, armed with our glittering lenses and our
flashing stands of exquisite workmanship, we search intently, but in vain.
And yet _not_ in vain, for we are more than recompensed by the wondrous
revelations beheld and the unalloyed pleasures enjoyed, through the study
of even the unpretentious _Vaucheria_.
The amplification of the objects in the engravings is about 80 diameters.
* * * * *
JAPANESE CAMPHOR--ITS PREPARATION, EXPERIMENTS, AND ANALYSIS OF THE
CAMPHOR OIL.
[Footnote: From the Journal of the Society of Chemical Industry.]
By H. OISHI. (Communicated by Kakamatsa.)
LAURUS CAMPHORA, or "kusunoki," as it is called in Japan, grows mainly in
those provinces in the islands Shikobu and Kinshin, which have the southern
sea coast. It also grows abundantly in the province of Kishu.
The amount of camphor varies according to the age of the tree. That of a
hundred years old is tolerably rich in camphor. In order to extract the
camphor, such a tree is selected; the trunk and large stems are cut into
small pieces, and subjected to distillation with steam.
An iron boiler of 3 feet in diameter is placed over a small furnace, the
boiler being provided with an iron flange at the top. Over this flange a
wooden tub is placed, which is somewhat narrowed at the top, being 1 foot 6
inches in the upper, and 2 feet 10 inches in the lower diameter, and 4 feet
in height. The tub has a false bottom for the passage of steam from the
boiler beneath. The upper part of the tub is connected with a condensing
apparatus by means of a wooden or bamboo pipe. The condenser is a flat
rectangular wooden vessel, which is surrounded with another one containing
cold water. Over the first is placed still another trough of the same
dimensions, into which water is supplied to cool the vessel at the top.
After the first trough has been filled with water, the latter flows into
the next by means of a small pipe attached to it. In order to expose a
large surface to the vapors, the condensing trough is fitted internally
with a number of vertical partitions, which are open at alternate ends, so
that the vapors may travel along the partitions in the trough from one end
to the other. The boiler is filled with water, and 120 kilogrammes of
chopped pieces of wood are introduced into the tub, which is then closed
with a cover, cemented with clay, so as to make it air-tight. Firing is
then begun; the steam passes into the tub, and thus carries the vapors of
camphor and oil into the condenser, in which the camphor solidifies, and
is mixed with the oil and condensed water. After twenty-four hours the
charge is taken out from the tub, and new pieces of the wood are
introduced, and distillation is conducted as before. The water in the
boiler must be supplied from time to time. The exhausted wood is dried and
used as fuel. The camphor and oil accumulated in the trough are taken out
in five or ten days, and they are separated from each other by filtration.
The yield of the camphor and oil varies greatly in different seasons. Thus
much more solid camphor is obtained in winter than in summer, while the
reverse is the case with the oil. In summer, from 120 kilogrammes of the
wood 2.4 kilogrammes, or 2 per cent. of the solid camphor are obtained in
one day, while in winter, from the same amount of the wood, 3 kilogrammes,
or 2.5 per cent., of camphor are obtainable at the same time.
The amount of the oil obtained in ten days, _i.e._, from 10 charges or
1,200 kilogrammes of the wood, in summer is about 18 liters, while in
winter it amounts only to 5-7 liters. The price of the solid camphor is
at present about 1s. 1d. per kilo.
The oil contains a considerable amount of camphor in solution, which is
separated by a simple distillation and cooling. By this means about 20 per
cent. of the camphor can be obtained from the oil. The author subjected the
original oil to fractioned distillation, and examined different fractions
separately. That part of the oil which distilled between 180 deg.-185 deg. O. was
analyzed after repeated distillations. The following is the result:
Found. Calculated as
C_{10}H_{16}O.
C = 78.87 78.95
H = 10.73 10.52
O = 10.40 (by difference) 10.52
The composition thus nearly agrees with that of the ordinary camphor.
The fraction between 178 deg.-180 deg. C., after three distillations, gave the
following analytical result:
C = 86.95
H = 12.28
-----
99.23
It appears from this result that the body is a hydrocarbon. The vapor
density was then determined by V. Meyer's apparatus, and was found to be
5.7 (air=1). The molecular weight of the compound is therefore 5.7 x 14.42
x 2 = 164.4, which gives
H = (164.4 x 12.28)/100 = 20.18
or C_{12}H_{20}
C = (164.4 x 86.95)/100 = 11.81
Hence it is a hydrocarbon of the terpene series, having the general formula
C^{n}H^(2n-4). From the above experiments it seems to be probable that
the camphor oil is a complicated mixture, consisting of hydrocarbons of
terpene series, oxy-hydrocarbons isomeric with camphor, and other oxidized
hydrocarbons.
_Application of the Camphor Oil_.
The distinguishing property of the camphor oil, that it dissolves many
resins, and mixes with drying oils, finds its application for the
preparation of varnish. The author has succeeded in preparing various
varnishes with the camphor oil, mixed with different resins and oils.
Lampblack was also prepared by the author, by subjecting the camphor oil to
incomplete combustion. In this way from 100 c.c. of the oil, about 13
grammes of soot of a very good quality were obtained. Soot or lampblack is
a very important material in Japan for making inks, paints, etc. If the
manufacture of lampblack from the cheap camphor oil is conducted on a large
scale, it would no doubt be profitable. The following is the report on the
amount of the annual production of camphor in the province of Tosa up to
1880:
Amount of Camphor produced. Total Cost.
1877.......... 504,000 kins.... 65,520 yen.
1878.......... 519,000 " .... 72,660 "
1879.......... 292,890 " .... 74,481 "
1880.......... 192,837 " .... 58,302 "
(1 yen = 2_s_. 9_d_.)
(1 kin = 1-1/3lb.)
* * * * *
THE SUNSHINE RECORDER.
McLeod's sunshine recorder consists of a camera fixed with its axis
parallel to that of the earth, and with the lens northward. Opposite to the
lens there is placed a round-bottomed flask, silvered inside. The solar
rays reflected from this sphere pass through the lens, and act on the
sensitive surface.
[Illustration]
The construction of the instrument is illustrated by the subjoined cut, A
being a camera supported at an inclination of 56 degrees with the horizon,
and B the spherical flask silvered inside, while at D is placed the
ferro-prussiate paper destined to receive the solar impression. The dotted
line, C, may represent the direction of the central solar ray at one
particular time, and it is easy to see how the sunlight reflected from the
flask always passes through the lens. As the sun moves (apparently) in a
circle round the flask, the image formed by the lens moves round on the
sensitive paper, forming an arc of a circle.
Although it is obvious that any sensitive surface might be used in the
McLeod sunshine recorder, the inventor prefers at present to use the
ordinary ferro-prussiate paper as employed by engineers for copying
tracings, as this paper can be kept for a considerable length of time
without change, and the blue image is fixed by mere washing in water;
another advantage is the circumstance that a scale or set of datum lines
can be readily printed on the paper from an engraved block, and if the
printed papers be made to register properly in the camera, the records
obtained will show at a glance the time at which sunshine commenced and
ceased.
Instead of specially silvering a flask inside, it will be found convenient
to make use of one of the silvered globes which are sold as Christmas tree
ornaments.
The sensitive fluid for preparing the ferro-prussiate paper is made as
follows: One part by weight of ferricyanide of potassium (red prussiate) is
dissolved in eight parts of water, and one part of ammonia-citrate of iron
is added. This last addition must be made in the dark-room. A smooth-faced
paper is now floated on the liquid and allowed to dry.--_Photo. News._
* * * * *
BREAKING OF A WATER MAIN.
In Boston, Mass., recently, at a point where two iron bridges, with stone
abutments, are being built over the Boston and Albany Railroad tracks at
Brookline Avenue, the main water pipe, which partially supplies the city
with water, had to be raised, and while in that position a large stone
which was being raised slipped upon the pipe and broke it. Immediately a
stream of water fifteen feet high spurted out. Before the water could be
shut off it had made a breach thirty feet long in the main line of track,
so that the entire four tracks, sleepers, and roadbed at that point were
washed completely away.
* * * * *
A catalogue, containing brief notices of many important scientific papers
heretofore published in the SUPPLEMENT, may be had gratis at this office.
* * * * *
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