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terrestrial influence, when these bodies come swooping down upon the earth's atmosphere with a sun-generated velocity of nearly 24 or 25 miles per second, often superadded to the earth's velocity of 18 miles per second.

What could be gathered, then, from the great observed velocity of meteors would be inevitably this, that these bodies before reaching the earth had been travelling on paths far wider in range than the earth's orbit-that the aphelia (that is, the points of their orbit farthest from the sun) lay far out beyond the orbits of Jupiter and Saturn, perhaps even beyond the orbits of Uranus and Neptune.

But what amazing results would follow from this! It would no longer be possible to regard meteor systems as in any way associated with the earth's orbit. We should no longer be able to regard the earth's encounter with even a single meteor system as otherwise than a most wonderful coincidence, unless we concluded that besides that meteor system there were millions on millions of systems which lie altogether clear of her path. And remembering that she encounters many systems, we should have to abandon the belief that a wonderful coincidence was in question, and be forced to conclude that there must be countless millions of meteoric systems.

In other words, although in one year the earth
might cross the track of the meteors on or about
November 13, yet a long time after the path
would have so changed that the earth would not
encounter the meteors on that date, but somewhat
earlier or somewhat later.

But astronomers have a liking for certainty. I am inclined, indeed, to say that they have too great a liking for certainty, inasmuch as they often neglect evidence which, though founded on the laws of probability, is yet overwhelmingly strong. At any rate, in this instance, it is certain that very little confidence would have been placed in the researches of Schiaparelli, had not a very surprising confirmation been detected shortly after his results were promulgated.

If the August meteors have their family comet, why not the November meteors also? And as the actual figure of the meteor orbit was known in this instance-which was not the case with the August meteors when Schiaparelli began his researches there was here a means of proving definitely that meteors and comets are associated, if only a comet could be found which travels along that particular route in space which the November meteors traverse.

the meteors and the comet. Now it appeared that the path of the meteors (on the supposition mentioned) accords most closely with the comet's path-so far, at least, as the parts of both paths near the sun were considered.* The conclusion is obvious: an enormous weight of probability Now astronomers might have waited for many favours the belief that the coincidence is not years before they would have been able to verify accidental, but that, in some way (even now not the occurrence of such a change-but, fortunately, fully understood), the meteor system and the we have records of the occurrence of the Novem-comet are associated together. ber shower in long past years; so that all that was necessary was to compare the dates of those showers with the date on which the shower now takes place. The earliest recorded occurrence of star-shower belonging to what we now call the November system, took place on October 12, A.D. 902, (or in the new style on October 18); and, by comparing this with the date on which the shower now occurs (making due allowance for that peculiar motion of the earth's axis which causes the precession of the equinoxes), it appeared that the place where the earth encounters the meteors is steadily shifting forwards by about half a minute of arc in each year, so that a complete revolution of the place of encounter could be effected in about 30 x 360 or 10,800 years.* But when Professor Adams for the problem is one calculated to tax the highest powers even of mathematicians of his standing-came to examine the effects which the planets could produce on the meteoric paths, he found that this change of But no bright comets were found which could position was not accounted for on any of the be associated with the November meteors, and assumptions mentioned above. It became clear at first the search for faint ones was unsuccessthat the meteors are subject to disturbing attrac-ful. By one of those extraordinary coincidences, tions of a more effective character. In other however, with which the history of science has words, it seemed as though the meteors must familiarized us, a telescopic comet had but a travel out into regions where the giant planets, few months before been detected by Tempel, The occurrence of annual meteoric displays Jupiter and Saturn, or even Uranus and Neptune, the orbit of which (only calculated a few week had convinced all reasoning minds that the are capable of exerting more influence than they before Adams completed his labours) was found t meteors are cosmical bodies travelling on can exert on bodies travelling always near the to correspond very closely-or rather, in effect, planetary orbits around the sun. The matter earth's orbit. exactly with the track of the November meteors. was in effect certain, though it was often spoken It was an obvious consideration that, this being Thus quite a new light was thrown upon the of as a theory, even by astronomers capable of so, the real period of the meteors is, probably, nature of these wonderful meteor systems. appreciating the sound evidence on which it that same period-334 years or so-which sepa-pass over the later researches, which have shown rested. Another law of periodicity was to lead to rates the recurrence of marked meteoric displays that other well-known periodical meteor systems a further and even more important advance in belonging to this system. For with a period of are either associated with known comets or travel our knowledge respecting meteors. It was found 33 years, a body which along one part of its in orbits demonstrably eccentric. The two inthat one of the best recognised meteor systems- path crosses the earth's orbit, would along the stances above dealt with are quite sufficient to that which produces the November star shower-opposite path be far out in space, even beyond establish the important conclusion that the meteor waxed and waned in splendour within a period of the orbit of distant Uranus. systems are not in any way limited to the neighabout the third part of a century. In other The calculation of the motions of bodies travel-bourhood of the earth's orbit, but extend far out words, there was a rich part of the meteoric stream ling in such orbits is by no means an easy matter. into space along orbits of the most eccentric which returned to a particular position in the solar Astronomers, though they often have to deal with figure. system once in about 33 years. But whether the motions of bodies in very eccentric orbits, yet it returned in reality only once in that period, or are seldom required to follow those bodies along oftener, was not certain. If it had come back to the whole course of such orbits, or to trace out the same position, but during another month than those processes of change which affect the position November, we could have known nothing about and figure of the paths of such bodies. it, for the earth would have been "in another place." Astronomers were disposed to believe, in fact, that it did return several times in the course of the period of 331 years; for they could not believe that this rich region travelled out into space upon the enormous orbit corresponding to a

We shall see presently that the evidence is in reality even stronger than we are here supposing; but I do not hesitate to say that with no further evidence than the great observed velocity of meteors we should be led inevitably to the amazing inference that the solar scheme is crowded with meteoric systems. This inference would even then be no mere theory, but a legitimate conclusion from the evidence.

revolution having so long a period. They imagined that it returned to the place where the earth's orbit crosses the meteor track in about a year and a 33rd part, or in about a year less a 33rd part, and so came there at epochs passing round the circle of the months, either forwards or backwards, until after about 33 years the complete circuit had been formed, and so the display was renewed.

I shall now show how this view was shown by the great mathematician Adams to be unfounded, and the much more surprising results established that the members of the November meteor system have a period of 334 years, and travel out into space beyond the orbit of distant Uranus.

It happened, fortunately for science, that a method devised long ago by the eminent German astronomer Gauss was available for the solution of this difficult problem. Adapting this method with singular skill to the requirements of the problem before him, Adams found that the changes

The consequences of this result are most striking, and have hitherto not received a tithe of the attention which they merit.

(To be continued.)

MICROSCOPICAL JOTTINGS IN TOWN
AND COUNTRY.
No. II.

affecting the meteor's orbit are most satisfactorily W piece of cuttlebone, or as the learned call
E may now attempt the examination of our
accounted for on the supposition that the meteors it, Sepiostaire. We will commence by dividing
really travel out into space along the eccentric the bone" into halves across the axis with a
orbit which corresponds to the period of 33 years.
No doubt therefore remained, in the minds of
any who were capable of appreciating the evidence,
that the path of the November meteors really
carries them beyond the orbit of Uranus, or more
than nineteen times farther from the sun than
our earth is.

But, in the meantime, other and very remarkable evidence had been adduced which, at the same time, confirmed this result and proved that the August meteors also are travelling on an orbit yet more eccentric than that of the November meteor system.

From the laws of gravitation it follows that when once the period in which a body travels The Italian astronomer Schiaparelli had been round the sun is determined, the velocity of the led to notice that the bright comet of 1862 passed body at any given distance from the sun is also close by the earth's orbit at a point lying very known, let the figure of the body's path be what near the spot where she encounters the August it may. So that the astronomer could determine meteors. Now that comet travelled in a very with what actual velocity the November meteors eccentric path, having a period variously estimated enter the earth's atmosphere on any given assump- at from 126 to 145 years, but undoubtedly very tion as to their period. This known, he could, by very simple processes of calculation, determine from the apparent direction of the meteor's motion as they enter our atmosphere, what is the actual direction in which they are moving at that part of their path round the sun.

And thus it became possible to determine, on each of the above assumptions, what is the actual path traversed by the November meteors. But then, given their path, we know what forces come into play to sway their path into new positions. And if their path thus changes, the place where the earth encounters them must change also.

long. It occurred to Schiaparelli to inquire
whether, on the supposition that the August
meteors travel on an orbit of like eccentricity,
their calculated path would lie near that of the
comet. It will be understood that the meteors
might cross the earth's orbit in a million different

directions, not one of which would correspond
to a path placed like the comet's—though of like
figure.
So that the odds were enormously against
such a coincidence as Schiaparelli looked for,
supposing there were no real association between

*The read period is somewhat longer.

stout knife. With a keen razor we can now cut with perfect ease very thin sections of the bone, and placing one of these on our stage, we find that the bone consists of a great number of thin plates, separated from each other by vertical lamine of excessive delicacy, which wind in and about, reflecting upon themselves at intervals, so as to form a better support for the plates. Many have described these sinuous laminse as "pillars," but their true character is easily discoverable if we make a careful horizontal section, removing the calcareous plate," so that the tops of the so-called pillars may be seen. As opaques," these sections, when mounted on a black background, are very beautiful; but many persons prefer to mount vertical sections in balsam, in order that they may be viewed as polariscope objects. The number of beautiful slides that may be obtained from one piece of sepiostaire would surprise the novice. The outer horny case of the bone requires a different treatment, and would hardly be adapted to the hands of a beginner.

Before we leave, for a time at least, the sea*It is not to be therefore understood that the coinci dence is not equally close for the whole of the two paths. But where we only have the opportunity of observing the part of a body's path which lies close by the sun, we are not able (unless very many and very exact observations have been made, or unless the body has appeared more than once, so that we know its period) to determine very accurately the figure of the very remote parts of the path.

By Dr. Peters of Altona.

I

diately the muscles of the mouth, of the back of
the throat, and of the larynx, &c., contract, and
shut out the access of any other agent than the
atmospheric air.

side, we will glance at a few other objects that I
have secured at different periods. We may begin
with Polyzoa. The different species of Flustra
(sea-mats, &c.), found on all our coasts furnish
very good objects for the microscope of moderate If an animal whilst plunged under water, is pre-
power-and be it understood that I shall speak of vented from coming to the surface to breathe, at
nothing which a £3 3s. instrument will not show the end of a minute and a half it will appear to be
well, with the exception of polarizing, which quite dead, and the jaws will be firmly contracted.
would entail £1 10s. more. These must be care- By keeping the mouth open, and causing move-
fully washed with fresh water, and then mounted ments to be executed similar to those which are
either as
opaques," or in section as "trans-produced in the act of respiration, the animal
parents," in balsam. I have one slide-a Flustra will recover life in proportion as the air pene-
foliacea, found at Hornsea, Yorks-which comes trates into the lungs.
out grandly by polarized light. This Flustra is
composed of small oblong cells; the base mem-
brane of this is seen studded with a vast number
of beautifully coloured crosses, which "rotate
with the prism below the stage, when that is
rotated.

66

Dr. De Labordette tried this experiment on twelve animals of the same age and species (viz., rats), with the following results:-nine were restored, three died. But by prolonging the stay under water to two or three minutes, the limbs by degrees spread out, and the jaws were no longer contracted. Of twelve animals which had been immersed from two to three minutes, Dr. De Labordette, not without difficulty, restored only three: the others died.

The stiffness which follows death cannot be confounded with that which is produced in the subject whose stay under water has lasted only some moments. In the latter case, with subjects restored to life, the rigidity is the result of the contraction of the muscles; in the other case it is due to the rigor mortis. Section of the medulla oblongata causes the first species of contraction to give way, but is without effect in the case of rigor mortis. Eight animals presenting, after a short immersion in water, a strong contraction of the jaws, were submitted by M. Legros and Dr. De Labordette to section of the medulla oblongata, and immediately the contraction disappeared.

A parasitic Flustra, common on sea weeds, also furnishes a very pretty object for the inch objective. Of corallines, such as the "sickle," our shores commonly have an abundance; and these well mounted as opaques are not to be despised. Amongst the waifs of the shore we may generally find some very transparent crabshells, so transparent that they may be mounted "as they are," in balsam, and submitted to examination. We shall find in them certain "wheel crystals" of lime, which are noteworthy as revealing to us one stage in shell construction. These two are splendid polariscope objects. The skin of the prawn affords better specimens of these circular crystals, but generally these must be got at the shops, and can hardly come into the category of sea-side objects. The sea hedgehog, or Echinus, is tolerably well known to most of our readers; yet probably few of them have paid it the attention that it deserves. Let us take one from our The attempts to recover a drowned man from miscellaneous gatherings and give it a look over. the state of apparent death ought to be so much The "Aristotle's lantern," being the jaws of the the more persevering as the fact of the persistcreature, may first attract our notice. The teeth ence of the contraction of the jaws is almost which compose the jaw are five in number, and tantamount to a certainty of seeing them crowned each "tooth has somewhat the form of that of with success. If, unfortunately, life is extinct, the front of a rodent, save that its concave side is we have a sure sign of the inutility of any attempt strengthened by a projecting keel, so that a trans- at resuscitation in the spontaneous unclosing of verse section presents the appearance of '.' the teeth and the opening of the mouth. The tooth itself is composed of carbonate of lime, and is in structure essentially the same as the shell; the keel is composed of "cylindrical rods of carbonate of lime, having club-shaped ex- BY THE REV. E. KERNAN, CLONGOWES COLLEGE. tremities," and the "concave side of the tooth is coated with a firmer layer," which some have likened to the "enamel" of the teeth of vertebrata. These teeth are furnished with delicate

serrations, visible by thesis of the pocket lens, and the whole apparatus is interesting in the extreme. Around the jaws are a number of calcareous plates, easily removable, and to be mounted in balsam. These are interesting, inasmuch as they give a ready view of the structure of the shell and of the teeth. As polariscope objects, they too are good. The "spines" require to be sectioned, but though interesting, are not in our British species very remarkable.-H. P.

THE ACTION OF THE JAWS AND THE
PHARYNX IN DROWNING.

I

T is well known to most persons that by contracting the muscles of the jaws, the pharynx, and the roof of the palate, it is possible to prevent the entrance of air into the bronchi, and we are

enabled to plunge beneath the surface of the water, and remain there for some appreciable time. But it is not generally understood that, in the case of drowning animals, nature adopts this same method without effort on the part of the individual. Dr. A. De Labordette, after making numerous experiments on animals, believes that the contraction of the jaws, far from being a sign of death, shows rather the continuance of life; and he is strengthened in his conclusion by the fact that the Humane Society men, and all persons who have rescued and restored drowning persons, are agreed in declaring the existence of the contraction of the jaws. If we analyze the sensation which is experienced when we fall into water, we remember that we suffered for some time a violent constraint in the throat. We may swallow

N

SCIENCE FOR THE YOUNG.

(Continued from page 339.)

APPENDIX VI.

POLYGON OF FORCES.

determining by compositi in te is formed a
of any system of forces, there

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polygon, which begins with one of the forces,
continues by parallels equal to the other forces
in order, and is closed by the
final resultant. In Fig. 71,
P1 P2 P3 P4 P5, are a number
of forces acting on the point
X.

B

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STRAIN. DISPOSITION OF FORCES.

It may sometimes be of great importance to know what amount of strain is exerted in certain directions in which circumstances require that the forces keeping a body in equilibrium should act. A polygon of the forces at once shows their relative strength of action on the body. The absolute value of one force being known, that of the others can be calculated. Again, a number of known forces are at command, it is required to know how they should be placed to hold a body at rest. A polygon with sides as the forces, will show the direction each force should have.

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· Parallelopiped of Forces." The three sides of Fig. 73 are sufficient to give

FIG. 73

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a good general notion of this The important theorem. forces P Q S, acting on a body at X, are represented in direction and in magnitude by the sides of the solid figure. A frame such as shown is clamped upon the table of Fig. 64 as the polygon in Fig. 72. Cords, with proportional weights, are disposed along the sides of the frame, Fig. 73. The diagonal-the dotted line, equal and opposite to the diagonal-the body at X is in equilibrium.†

R

XX-shows the resultant.

Add the force R,

SUB-APPENDIX 1.
PRACTICAL QUESTIONS.

Combining P1 and P, A there is produced the side PA, parallel to P. Continuing the combinations as in Law VI., there is produced: A B parallel to P3, BC parallel to P, CD parallel to P, and tant matters of every day utility, depend up Some interesting facts, and some most impor DX closes the polygon. For the principle contained in the parallelopiped d equilibrium R X, a force forces. Were the subject not too difficult, the equal and opposite to C X, is practical questions should be studied separatel added. Therefore, this sys-Por the present little more than the indication of tem of forces in equilibrium is represented by the them can be given. I. Bellringers.-Large heavy polygon PA BCDX. Its sides being equal and bells require a number of men to make the parallel in order to the six balanced forces, show their relative intensities and direction. Such is the meaning of the "Polygon of Forces."

It does not signify, then, that the forces form a polygon, but they may be represented by a polygon, the sides of which show their direction and relative magnitude. It may be found enounced in other words, but these do not convey anything really different from what has been just stated.

For experiment, the theorem is reversed, "forces of relative magnitude, as the sides of a given polygon, are in equilibrium when acting upon a point if they be disposed in order parallel to the sides which represent their magnitudes."

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where the greatest strength must be in the riggin how the various stays should be placed, but not breathe, and when we come out of the and other as 4, 2, 5, 3, 1. This polygon (of wood) be required to cut away," principles of cal In the polygon A, Fig. 72, the sides are to one On the contrary, when, in case of storm, it may water we still preserve for a long time the sensa- being clamped on to the table of the apparatus in culation will show where to cut, that the sour tion of contraction and constriction of the throat. Fig. 64, cords are disposed, Fig. 72 (from a ring, of danger be removed with all speed. Let any cause or agent intervene to threaten the D, held by a pin to the wood), parallel to the Moorings.-The safety of all floating bodies. respiratory function in its physiological condi- sides of the polygon, by means of the pulleys, tions, the sensitive disturbance which the pneumo- on the frame.* Weights proportional, as 4, gastric nerve receives from it instantly causes the motor nerves-the spinal, hypoglossal, and the pulleys are nearer than they should be if the whole appa*The frame is omitted in the present figure, and the laryngeal nerves-to enter into action, and imme-ratus were given.

*The figures at the weights show the lines to which the forces are parallel. Thus, 1 shows that the line 101

Frames of any solid figure, acute angle, &c. &c., misy be used as the rectangular frame of Fig. 73.

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ships' batteries, lights, &c., will depend upon the disposition of the chains and ropes which form their moorings. From the parallelopiped can be drawn the changes or additions which the ordinary run of circumstances may require. IV. Suspension bridges. As these are but little exposed to the action of violent unexpected forces, their equilibrium-conditions of security-as far as their concurrent forces are concerned, can be calculated with great exactitude by the parallelopiped of forces.

SUB-APPENDIX II. INSECT STRENGTH.

MECHANICAL MOVEMENTS. The the relative strength of the forces is seen. effect of a c is to bend the nail, a d passes on to the point e. There a d, transferred, decomposes again, say into e g and e h. If the nail point be not well fixed e g takes effect; if the wood can resist, e h has some small effect in sinking the point further. Many other possible decompositions of A B would show greater or less force, tending to bend or displace the nail.

APPENDIX IX.

ROPES, CHAINS, ETC.

The utility of every sort of cord, rope, wire, Some time ago (1866) Mr. Felix Plateau pub- chain, &c., from the finest to the most massive, lished in the Bulletin de l'Academie Belgique arises from their being able to offer an equal and a most interesting series of papers on the strength opposite force to force brought to act upon them. of insects compared with that of higher animals.* It is "tenacity" which gives them this power up In this comparison of weight to work, Mr. Plateau to a certain point. found that while a horse can only do work equal to two-thirds of his weight, none of the insects are lower in work than four times their weight; some reach to 12, 15, 25, 42 times their weight. Mr. Plateau seems to have arrived at an experimental law, that their power of traction or of pushing is inversely as the weight and size of the insects. Granting the existence of great comparative muscular power, there can be no doubt but that the parallelopiped formed by the multiplication of feet, often armed with claws-curved claws-in many of the insect tribes, enables them to apply their power in a concentrated manner impossible to the horse.

APPENDIX VIII.

A BLOW, FULL FORCE OF.

A blow can never have its full effect unless its direction be along the desired line of effect. Thus, in driving a nail with a ham

FIC.75

B 5.6.76

C

is.

Thus far the applications of lesser importance. Now are to be seen (studied) some of the so-called "machines," or "mechanical powers." Their most complete explanation depends only on the principles of force applied to a point. As the machines are of great practical utility, they shall be treated in four points. I.-What the machine II. What is the principle of its action. III.-The conditions of equilibrium, established when possible by mathematical reasoning and formula. IV. The development-uses of the machine-and sub-applications. Even these have their applications, sometimes very important. They shall be distinguished from the general applications of the laws, by the name of the machine to which they belong.

MECHANICAL MOVEMENTS.*
(Continued from page 344.)

193.Contriverical form. The polishing material for polishing lenses and bodies is in a cup connected by a ball-and-socket joint and bent piece of metal with a rotating upright shaft set concentric to the body to be polished. The cup is set eccentric, and by that means is caused to have an independent rotary motion about its axis on the universal joint, as well as to revolve about the common axis of the shaft and the body to be polished. This prevents the parts of the surface of the cup from coming repeatedly in contact with the same parts of surface of the lens or other body.

mer, Fig. 75, the force must act along the line A B, the axis of the nail. Should it strike along AC the force is decomposed, part goes along A C, part along A B. Hence the endeavour to drive a crooked nail is a great waste of force, frequently having little more effect than to increase the crookedness. The study of this well-known fact affords an easy exercise in the decomposition of forces. The force of the hammer is shown in direction and intensity by the line A B, Fig. 76. That force 195. Four-way cock, used many years ago on may be decomposed into two; say one at right steam engines to admit and exhaust steam from angles to the axis (of the nail) a b, and another the cylinder. The two positions represented are along the axis a b. Completing the parallelogram produced by a quarter turn of the plug. Supposing *Extracted from a compilation by Mr. H. T. BROWN, Editor of the "American Artisan.'

B

* Les Mondes, vol. i. p. 36, and vol. iv. p. 81.

194. C. Parson's patent device for converting reciprocating motion into rotary-an endless rack provided with grooves on its side gearing with a pinion having two concentric flanges of different diameters. A substitute for crank in oscillating cylinder engines.

the steam to enter at the top, in the upper figure the exhaust is from the right end of the cylinder, and in the lower figure the exhaust is from the left

thesteam entering, of course, by the opposite port. 196. G. P. Reed's patent anchor and lever escapement for watches. The lever is so applied in cembination with chronometer escapement that the whole impulse given balance in one direction is transmitted through the lever, and whole impulse in opposite direction is transmitted directly to chronometer impulse pallet, locking and unlocking the escape-wheel but once at each impulse given by said wheel.

197. Continuous circular into intermittent rec

tilinear reciprocating. A motion used on several sewing machines for driving the shuttle. Same motion applied to three-revolution cylinder printing

presses.

198. Continuous circular motion into intermittent circular-the cam, C, being the driver.

199. A method of repairing chains, or tightening chains used used as guys or braces. Link is made in two parts, one end of each is provided with swivelnut, and other end with screw; the screw of each part fits into nut of other.

200. Four-motion feed (A. B. Wilson's patent), used on Wheeler & Wilson's, Sloat's, and other sewing machines. The bar A is forked, and has a second bar, B (carrying the spur or feeder), pivoted in the said fork. The bar, B, is lifted by a radial projection on the cam, C, at the same time the two bars are carried forward. A spring produces the return stroke, and the bar, B, drops of its own gravity.

201. E. P. Brownell's patent crank-motion to obviate dead centres. The pressure on the treadle causes the slotted slide, A, to move forward with the wrist until the latter has passed the centre, when the spring, B, forces the slide against the stops until it is again required to move forward.

202. G. O. Guernsey's patent escapement for watches. In this escapement two balance-wheels are employed, carried by the same driving-power, but counteracting the effect of any sudden jar upon a oscillating in opposite directions, for the purpose of watch or time-piece. The jar which would accelerate motion of one wheel would retard the motion of other. Anchor, A, is secured to lever, B, having an interior and exterior toothed segment at its end, each one of which gears with the pinion of balancewheels.

203. Cyclograph for describing circular arcs in drawings where the centre is inaccessible. This is composed of three straight rules. The chord and versed sign being laid down, draw straight sloping lines from ends f former to top of latter, and to these lines lay two of the rules crossing at the apex. Fasten these rules together, and another rule across them to serve as a brace, and insert a pin or point at each end of chord to guide the apparatus, which, on being moved against these points, will describe the arc by means of pencil in the angle of the crossing edges of the sloping rules.

204.

Another cyclograph. The elastic arched bar is made half the depth at the ends that it is at the middle, and is formed so that its outer edge coincides with a true circular arc when bent to its greatest extent. Three points in the required are

of the

being given, the bar is bent to them by means
screw, each end being confined to the
straight bar by means of a small roller.
205. Mechanical means of describing hyperbolas,
their foci and vertices being given. Suppose the
curves two opposite hyperbolas, the points in
vertical dotted centre line their foci. One end of
rule turns on one focus as a centre through which
one edge ranges. One end of thread being looped
on pin inserted at the other focus, and other end
held to other end of rule, with just enough slack
between to permit height to reach vertex when rule
coincides with centre line. A pencil held in bight,
and kept close to rule while latter is moved from
centre line, describes one-half of parabola; the rule
is then reversed for the other half.

206. Mechanical means of describing parabolas, the base, altitude, focus, and directrix being given. Lay straight edge with near side coinciding with directrix, and square with stock against the same, so that the blade is parallel with the axis, and proceed with pencil in bight of thread, as in the preceding.

207. Instruments for describing pointed arches. Horizontal bar is slotted and fitted with a slide having pin for loop of cord. Arch bar of elastic wood is fixed in horizontal at right angles. Horizontal bar is placed with upper edge on springing line, and back of arch bar ranging with jamb of opening, and the latter bar is bent till the upper side meets apex of arch, fulcrum-piece at its base insuring its retaining tangential relation to jamb; the pencil is secured to arched bar at its connection

with cord.

208. Centrolinead for drawing lines toward an inaccessible or inconveniently distant point; chiefly used in perspective. Upper or drawing edge of blade and back of moveable legs should intersect centre of joint. Geometrical diagram indicates mode of setting instrument, legs forming it may form unequal angles with blade. At either end of dotted line crossing central, a pin is inserted vertically for instrument to work against. Supposing it to be inconvenient to produce the convergent lines until they intersect, even temporarily, for the purpose of setting the instrument as shown, a corresponding convergence may be found between them by drawing a line parallel to and inward from each. (To be continued.)

I'

WHAT IS ENERGY."

IN TWO PARTS.-PART I.

dually, and by very slow steps, the true nature of
work came to be understood. It was seen, for in-
stance, that it involved a much less expenditure of
energy for a man to carry a pound weight along a
level road than to carry it an equal distance up to
the top of a mountain.

It is not improbable that considerations of this
kind may have led the way to a numerical estimate
of work.

it has the power of doing useful work or of over coming up to a great height the obstacle interd by gravity to its ascent, just as a man of great energy has the power of overcoming obstacles. But this stone as it continues to mount upwards will di so with a gradually decreasing velocity, until at the summit of its flight all the actual energy with which it started will have been spent in raising r against the force of gravity to this elevated positic It is now moving with no velocity-just, in ta beginning to turn-and we may suppose it to b caught and lodged upon the top of a house. Her then, it remains at rest, without the shiple tendency to motion of any kind, and we are led ask what has become of the energy with whics began its flight? Has this energy disappeared fr the universe without leaving behind it any equ lent? Is it lost for ever, and utterly wasted? the answer to this question must be reserved: another article.

Thus, if we raise a pound weight one foot high against the force of gravity we may call it one unit of work, in which case two pounds raised one foot high, or one pound raised two feet high, would represent two units, and so on. We have therefore only to multiply the number of pounds by the vertical height in feet to which they are raised, and the product will represent the work done against gravity. The force of gravity being very nearly constant at the earth's surface, and always in action, is a very convenient force for this purpose; but any other force, such as that of a spring, would do equally well to measure work by. Generalizing, we may say, the space mored over against a force multiplied ON THE RELATIONS BETWEEN BODY AF into the intensity of that force will represent the quantity of work done. So much for the definition of work, and it is necessary to know what work is before proceeding to define Energy.

Now what does the word energy mean? In the

in

first place it does not mean force.
Two substances may have an intense mutual
attraction, in virtue of which they form a very
tinate union with one another; but when once this
union has been consummated, although the force
still continues to exist, the combination is singu-
larly deficient in energy. Nor does energy mean
motion, for although we cannot have motion with-
out energy, yet we may have energy without
motion.

By the word energy is meant the power of doing
work; and the energy which a labouring man
possesses means, in the strictly physical sense, the
number of units of work which he is capable of
accomplishing.

MIND.*

(Concluded from page 342.)

HE different forms of insanity that occ

THE

young children-as all forms of it exe able to nervous disease in the preceding generati general paralysis may do-are almost always tra element in their causation. The cases of act a neuropathic condition being really the essentia mania in children of a few weeks or a few years d which have been described right more properly b classed as examples of idiocy with excitement There can be no true mania until there is some mind; but we do meet sometimes in older children with a genuine acute mania, occurring usually in connection with chorea or epilepsy, and presenting the symptoms, if I may so express it, of a mental chorea or an epilepsy of the mind, but without the spasmodic and convulsive movements of these diseases. More or less dulness of intelligence and apathy of movement, giving the seeming of a degree of imbecility, is cominon enough in chorea, and in The analogy which we shall venture to institute some cases there is violent delirium; but, besides is between the social and the physical world, in the choreic disorder of movements, there is a choreic these cases, there are others in which, without hope that those who are more familiar with themania: it is an active delirium of ideas which is former than with the latter may be led to perceive the counterpart of the usual delirium of moveclearly what is meant by the word energy in a ments, and its automatic character and its marked strictly physical sense. Energy in the social world incoherence are striking enough to an ordinary is well understood. When a man pursues his course, observer. Hallucinations of the special senses, and undaunted by opposition and unappalled by ob- loss or perversion of general sensibility, usually stacles, he is said to be a very energetic man. accompany the delirium, the disorder affecting the centres of special and general sensation, as well as the mind-centres.

This is a subject which at this stage we may attempt to illustrate by reference to a very different department of knowledge.*

T is only of late years that the laws of motion By his energy is meant the power which he have been fully comprehended. No doubt it possesses of overcoming obstacles; and the amount has been known since the time of Newton that of this energy is measured (in the loose way in which there can be no action without reaction; or, in we measure such things) by the amount of obstacles other words, if we define momentum to be the pro- which he can overcome the amount of work duct of the mass of a moving body into its velocity which he can do. Such a man may in truth be reof motion, then whenever this is generated in one garded as a social cannon ball. By means of his direction an equal amount is simultaneously gene-energy of character he will scatter the ranks of his rated in the opposite direction, and whenever it is opponents and demolish their ramparts. Neverthe. destroyed in one direction an equal amount is simul- less, a man of this kind will sometimes be defeated taneously destroyed in the opposite direction. Thus by an opponent who does not possess a tithe of his the recoil of gun is the appropriate reaction to t. e personal energy. Now, why is this? A reply to forward motion of the ballet, and the ascent of a this question will, if we do not mistake, exhibit in rocket to the downrush of heated gas from its ori- a striking manner the likeness that exists between fice; and in other cases where the action of the the social and the physical world. The reason is principle is not so apparent, its truth has notwith- that, although his opponent may be deficient in standang been universally admitted. personal energy, yet he may possess more than an It has, for instance, been perfectly well under-equivalent in the high position which he occupies, stood for the last 200 years that if a rock be de- and it is simply this position that enables him to tached from the top of a precipice 144 ft. high it combat successfully with a man of much greater will reach the earth with the velocity of 96 ft. in a se-personal energy than himself. If two men throw cond, while the earth will in return move up to meet stones at one another, one of whom stands at the it, if not with the same velocity yet with the same top of a house and the other at the bottom, the momentum. But inasmuch as the mass of the earth man at the top of the house has evidently the ad is very great compared with that of the rock, so the vantage. velocity of the former must be very small compared with that of the latter, in order that the mo

So, in like manner, if two men of equal personal energy contend together, the one who has the mentum or product of mass into velocity may be highest social position has the best chance of sucthe same for both. In fact, in this case, the velo- ceeding. For this high position means energy city of the earth is quite insensible and inay be dis-under another form. It means that at some remote regarded. period a vast amount of personal energy was expended in raising the family into this high position. The founder of the family had, doubtless, greater energy than most of his fellows, and spent it in raising himself and his family into a position of advantage. The personal element may have long since disappeared from the family, but not before it had been transmuted into something else, in virtue of which the present representative is able to accomplish a great deal, owing solely to the high position which he has acquired through the efforts of another. We thus see that in the social world we have what may justly be termed two kinds of energy, namely:

The old conception of the laws of motion was thus sufficient to represent what takes place when the rock is in the act of traversing the air to meet the earth; but, on the other hand, the true physical concomitants of the crash which takes place when the two bodies have come together were entirely ignored. They met, their momentum was caucelled-that was enough for the old hypothesis.

So, when a hammer descends upon an anvil, it was considered enough to believe that the blow was stopped by the anvil; or when a break was applied to a carriage wheel it was enough to imagine that the momentum of the carriage was stopped by friction. We shall presently allade to the names of those distinguished men who have come prominently forward as the champions of a juster concep tion of things; but in the mean time let us consider some of those influences which served to prepare men's minds for the reception of a truer hypothesis. We live in a world of work, of work from which we cannot possibly escape; and those of us who do not require to work in order to eat, must yet in some sense perform work in order to live. GraBy BALFOUR STEWART, in Nature.

1. Actual or personal energy.

2. Energy derived from position.
Let us now again turn to the physical world. In
this, as in the socia lworld, it is difficult to ascend.
The force of gravity may be compared to that force
which keeps a man down in the world. If a stone
he shot upwards with great velocity, it may be said
to have in it a great deal of actual energy, because

* The subject has previously been discussed from this
point of view by Messrs. Stewart and Lockyer in an
article in Macmillan's Magazine, August, 1868.

there are intermediate conditions partaking more or
Between this choreie mania and epileptic mania
less of the character of one or the other-hybrid
hours or days in a seeming ecstasy or trance, with
forms of a cataleptic nature. The child will lie for
its limbs rigid or fixed in a strange posture.
There may be apparent insensibility to impressions.
while at other times vague answers are given, or
there is a sudden bursting out into wild shrieks or
incoherent raving. If this be of a religious kind,
the child is apt to be thought by ignorant persons
to be inspired. The attacks are of variable dura-
tion, and are repeated at varying intervals. On the
one hand, they pass into attacks of chorea; and, on
nate with them.
the other hand, into true epileptic seizures, or alter

mania, a genuine mania transitoria, may precede,
In children, as in adults, a brief attack of violen
follow, or take the place of an epileptic fit; in th
latter case being a masked epilepsy. Children
three or four years of age are sometimes seized wi
attacks of violent shrieking, desperate stubbornes

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whi or furious rage, when they bite, tear, kick, and 3 cally, and may either pass in the course of a fer are a sort of vicarious epilepsy, come on perial months into regular epilepsy, or may alternate wi it. Older children have perpetrated crimes of savage and determined nature-incendiarism. ars of transitory fury, followed or not by epileptic even murder-under the influence of similar attacks vulsions. It is of the utmost importance to realise the deep effect which the epileptic neures may have on the moral character, and to keep mind the possibility of its existence when a savage apparently motiveless, and unaccountable crime been committed. A single epileptic seizure been known to change entirely the moral charact rendering a child rude, vicious, and perverse, was hitherto gentle, amiable, and tractable. one who has seen it can fail to have been struck with the great and abrupt change in moral cha racter which takes place in the asylum epileptic intervals between them he is often an amiable, immediately before the recurrence of his fits: in the obliging, and industrious being, but when they im pend he becomes, sullen, morose, and most dan then foretell that he is going to have his fits, as gerous to meddle with. Not an attendant but call

* Two lectures delivered at the Royal College of Phy sicians in 1870. By HENRY MAUDSLEY, M.D., F.R.C Professor of Medical Jurisprudence in Universit

College, Londor.

onfidently almost as he can foretell that the sun will ise next day. Morel has made the interesting obserFation, which is certainly well founded, that the peptic neurosis may exist for a considerable period an undeveloped or masked form, showing itself, ot by convulsions, but by periodic attacks of mania, by manifestations of extreme moral perversion, Lich are apt to be thought wilful viciousness. But they are not-no moral influence will touch them: hey depend upon a morbid physical condition, hich can only have a physical cure; and they get heir explanation, and indeed justification, aftervards, when actual epilepsy occurs.

The epileptic neurosis is certainly most closely allied to the insane neurosis; and when it exists in its masked form, affecting the mind for some time before convulsions occur, it is hardly possible to listinguish it from one form of the insane neurosis. The difficulty of doing so is made greater, inasmuch is epilepsy in the parent may engender the insane eurosis in the child, and insanity in the parent he epileptic neurosis in the child. A character which the insane neurosis has in common with the epileptic neurosis is that it is apt to burst out in a convulsive explosion of violence; that when it develops into actual insanity it displays itself in deeds rather than in words-in an insanity of action rather than of thought. It is truly a neurosis spas nodica. Take, for example, a case which is one of a class-that of the late Alton murderer, who, taking a walk one fine afternoon, met some little girls at play, enticed one of them into a neighbouring hopgarden, there murdered her and cut her body into fragments, which he scattered about-returned quietly home, openly washing his hands in the river on the way-made an entry in his diary, "Killed a little girl; it was fine and hot "-and when forthwith taken into custody, confessed what he had done, and could give no reason for doing it. At the trial it was proved that his father had had an attack of acute mania, and that another near relative was in confinement, suffering from homicidal mania. He himself had been noted as peculiar: he had been subject to fits of depression, been prone to weep without apparent reason, and had exhibited singular caprices of conduct; and it had once been necessary to watch him from fear that he might commit suicide. He was not insane in the legal or the ordinary sense of the term, but he certainly had the insane neurosis, and it may be presumed confidently that he would, had he lived, have become insane.

Those who have practical experience of insanity know well that there is a most distressing form of the disease, in which a desperate impulse to commit suicide or homicide overpowers and takes prisoner the reason. The terrible impulse is deplored sometimes by him who suffers from it as deeply as by any one who witnesses it; it causes him unspeakable distress; he is fully conscious of its nature, and struggles in vain against it; his reason is no further affected than in having lost power to control, or having become the slave of, the morbid and convulsive impulse. It may be that this form of derangement does sometimes occur where there is no hereditary predisposition to insanity, but there can be no doubt that in the great majority of cases of the kind there is such a neuropathic state. The impulse is truly a convulsive idea springing from a morbid condition of nerve element, and it is strictly comparable with an epileptic convulsion. How grossly unjust, then, the judicial criterion of responsibility which dooms an insane person of this class to death if he knew what he was doing when he committed a murder! It were as unreasonable to hang a man for not stopping by an act of will a convulsion of which he was conscious. An interesting circumstance in connection with this morbid impulse is that its convulsive activity is sometimes preceded by a feeling very like the aura epileptica -a strange morbid sensation, beginning in some part of the body, and rising gradually to the brain. The patient may accordingly give warning of the impending attack in some instances, and in one case was calmed by having his thumbs loosely tied together with a ribbon when the forewarning occurred. Dr. Skae records an instructive

fits, for evidence of an aura epileptica and other symptoms allied to epilepsy.

It is worth while observing that in other forms of insanity, when we look closely into the symptoms, there are not unfrequently complaints of strange, painful, and distressing sensations in some part of the body, which appear to have a relation to the mental derangement not unlike that which the epileptic aura has to the epileptic fit. Common enough is a distressing sensation about the epigastrium. It is not a definite pain, is not comparable strictly to a burning, or weight, or to any known sensation, but is an indescribable feeling of distress to which the mental troubles are referred. It sometimes rises to a pitch of anguish, when it abolishes the power to think, destroys the feeling of identity, and causes such unspeakable suffering and despair that suicide is attempted or effected. In other cases the distressing and indescribable sensation is in the crown of the head or down the spine, and sometimes it arises from the pelvic organs. In all cases the patients connect their mental trouble with it, regarding it as the cause of the painful confusion of thought, the utter inability of exertion, the distressing ideas, and the paroxysm of despair. Perhaps they exaggerate its importance; but there can be little doubt that writers on mental disorders, too exclusively occupied with the prominent mental features, have not hitherto given sufficient attention to these anomalous sensations. We have been apt to class them as hypochondriacal, and to pass them over as of no special significance; but I cannot help thinking that, properly studied, they may sometimes teach us more of the real nature of the particular form of insanity-of its probable course, termination, and its most suitable treatment-than many much more obtrusive symptoms.

the Croesor mountain, and runs downwards at an angle of 40° with the horizon; the purpose of this awkward incline being to get more quickly at that portion of the slate vein into which the company wish to quarry. The shaft is 8ft. high, and 10ft. broad, running through hard bastard slate very full of iron pyrites, and crossed by hard bands of quartz.

The borer is shown in our engraving at work in the inclined shaft. The machine consists of a hori zontal base, a a, coupled by four links with the motor (B)-an air-engine-behind it. Within the base, a a, a horizontal shaft rotates, receiving its motion through a palley and belt from the fly-wheel of the engine. The vertical columns, c, c1, have each a shaft revolving in their interior for giving motion to the boring tools, d, d1. The vertical and horizontal shafts are coupled together by means of bevel gear, the followers being fixed upon the bottom ends of the vertical shafts, and the leaders running in longitudinal grooves cut in the hori zontal shaft, and being held in place by suitable bridles.

Each upright shaft has two (sometimes three) similar bevel wheels, each engaging with the corre sponding wheel of a boring tool. With this arrangement the vertical shafts can at any moment be shifted horizontally-either brought together or separated-by means of screws, e, e, working in suitable nuts fixed to the bases of the columns. The elevation of the boring tools can also be changed at pleasure, and they can be "angled" through any desired range; in one direction by the columns being turned round their vertical axes, in the other direction by the boring tools being turned in a vertical plane.

The

The boring tool is fixed at the end of a long screw, a nut upon which revolves with it, being conIn bringing this lecture to an end, I may fitly point nected with the driving gear by a friction clutch. out how entirely thus far the observation of the The wheel which imparts direct rotation to the drill phenomena of defective and disordered mind proves has one tooth more than that which presses against their essential dependence on defective and dis- the nut. A differential motion is thereby obtained, ordered brain, and how closely they are related to which causes the boring tool to advance a certain some other disordered nervous functions. The in- distance with every revolution, unless the resistsane neurosis which the child inherits in conse-ance which it meets in the rock becomes too great, quence of its parent's insanity is as surely a defect when the clutch slips and prevents breaking the of physical nature as is the epileptic neurosis to tool. which it is so closely allied. It is an indisputable, though extreme fact, that certain human beings are born with such a native deficiency of mind that all the training and education in the world will not raise them to the height of brutes; and I believe it to be not less true that, in consequence of evil ancestral influences, individuals are born with such a flaw or warp of nature that all the care in the world will not prevent them from being vicious or criminal, or becoming insane. Education, it is true, may do much, and the circumstances of life may do much; but we cannot forget that the foundations on which the acquisitions of education must rest are not acquired but inherited, No one can escape the tyranny of his organization No one can elude the destiny that is innate in him, and which unconsciously and irresistibly shapes his ends, even when he believes he is determining them with consummate foresight and skill. A wellgrounded and comprehensive theory of mind must recognize and embrace these facts: they meet us every moment of our lives, and cannot be ignored if we are in earnest in our attempts to construct a mental science; and it is because metaphysical mental philosophy has taken no notice whatever of them because it is bound by the principle of its existence as a philosophy to ignore them-that, notwithstand ing the labour bestowed on it, it has borne no fruits -that, as Bacon said of it, "not only what was asserted once is asserted still, but what were questions once are questions still, and, instead of being resolved by discussion, are only fixed and fed."

To avoid the heating of the drills by friction, and to lubricate them, a constant stream of cold water is kept flowing through them. For this purpose they are made hollow, and the water, entering through the elastic tubes, g, g, passes through the drill, during the time it is at work, and flows out of the bore through the space left between the diameter of the hole and that of the drill. motor, B, attached to the boring machine, consists of an engine worked by compressed air, which is forced down the shaft through a gaspipe, D, D. This machine has to fulfil the double duty of working the drills and of pumping back the water which has passed through them to keep them cool and to lubricate them. The construction of this engine offers no point of novelty beyond the arrangement of the cylinder, which has the slide valve and the exhaust upon opposite sides in order to facilitate the clearing out of the exhausts in the event of their getting choked by ice formed by the refrigeration of water vapour upon the expansion of the air in escaping. The blast of cold air issuing from the exhaust of the motor thoroughly ventilates the shaft and keeps the air in it exceptionally clear and cool. Before the machine is raised or lowered in the shaft the two upper coupling links are drawn back by screws at the sides of the motor carriage upon which their lower ends are held. This causes the vertical columns, c, c1, to be tilted backwards until the base, a a, is brought to rest upon two hind wheels which run upon the metals forming the tramway as shown in the drawing.

The air which works this machine down in the shaft is compressed and supplica by a turbine in the DIAMOND ROCK-BORING MACHINE AT THE valley below; and this turbine is worked by a head

CROESOR SLATE QUARRIES.
(Illustrated at page 373.)

WE recently had an opportunity of visiting the works of the Croesor United Slate Coinpany's Quarries, in Carnarvonshire, and were much interested by the process by which a new and difficult shaft is being driven into the side of the mountain. Hitherto only hand labour has been employed for driving headings in these quarries; but the necessity of pushing on some new work with greater speed than could possibly be got by hand labour, has induced the company to call in the aid of the diamond boring machine, with the proprie tors of which, Captain Beaumont, R.E., and Mr. C. Appleby, they have entered into a contract.

in one of his annual reports. The feeling begample the toes, rose gradually to the chest, producing a sense of faintness and constriction, and then to the head, producing a momentary loss of consciousness. This aura was accompanied by an involuntary jerking-first of the legs, and then of the arms. It was when these attacks came on that the patient felt impelled to commit some act of violence to others or to himself. On one occasion he attempted to commit suicide by throwing himself into the water: more often the impulse was to attack others. He deplored his condition, of which he spoke with great intelligence, giving all the details of his past Amongst the various propositions which have been history and feelings. In other cases a feeling of brought into notice for machine tunnelling, one of vertigo, a trembling, and a vague dread of some- the most courageous and successful is that in which thing fearful being about to happen, resembling the a coarse cheap kind of diamond is used to form the vertigo and momentary vague despair of one variety head of the cutting tool. Since the introduction of of the epileptic aura, precede the attack. Indeed, the system, it has, of course, worked its way whenever a murder has been committed suddenly, without premeditation, without malice, without motive, openly, and in a way quite different from the way in which murders are commonly done, we ought to look carefully for evidence of previous epilepsy, and, should there have been no epileptic

through many stages before it arrived at being a practical reality. The work it is getting through at this moment, however, puts its capabilities to a trial which cannot leave a doubt as to its efficiency. The shaft which is being driven commences at an elevation of some hundreds of feet above the foot of

of water conducted to it from a tank on the side of the opposite hill. The tank is fed from a small mountain lake which is perched among the hills high above the sea level, and which has been dammed up and provided with a sluice for the purpose. The tank into which the lake-water flows is 350ft. above the turbine, with which it is connected by a 6in. castiron pipe. The turbine works a double action airpump, and the compressed air is conducted up to the mouth of the shaft through a 4in, cast-iron pipe, and from the mouth down into the shaft to the machine, through a 2in. pipe, till near the machine, where the connection is made with a flexible hose. This compressed air is applied to three purposes: it drives the horer, it pumps water out of the shaft, and it starts the hauling-up drum.

The rope by which the loaded wagons are drawn up out of the shaft is worked on the tail-end system upon an opposite incline outside the shaft. The tail-end of the rope is attached to a wooden tank which runs down upon a tramway. When the wagon is down the shaft, the tank is drawn up under a shoot connected with a mountain stream which fills it. When full, its weight in running down its incline is sufficient to draw up the full wagons out of the pit. When it reaches the bottom of its incline, a valve in the bottom of the travelling tank is opened automatically and the water runs.

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