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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 mile» 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 fur 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 I 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.

We shall see presently that the evidence is in reality even stronger than we are hero 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.

The occurrence of annual meteoric displays had convinced all reasoning minds that the meteors are cosmical bodies travelling on planetary orbits around the sun. The matter was in effect certain, though it was often spoken of as a theory, even by astronomers capable of appreciating the sound evidence on which it rested. Another law of periodicity was to lead to a further and even more important advance in our knowledge respecting meteors. It was found that one of the best recognised meteor systems— that which produces the November star shower— waxed and waned in splendour within a period of about the third part of a century. In other words, there was the rich part of the meteoric stream which returned to a particular position in the solar system once in about MI years. But whether it returned in reality only once in that period, or oftener, was not certain. If it had come back to the same position, but during another month than November, we could have known nothing about 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 33} years; for they could not believe that this rich region travelled out into space upon the enormous orbit corresponding to a revolution having во long a period. They imajgined 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 Mt years, and travel out into space beyond the orbit of distant Uranus.

From the laws of gravitation it follows that when once the period in which a body travels round the sun is determined, the velocity of the body at any given distance from the sun is also known, let the figure of the body's path be what it .may. Bo that the astronomer could determine with what actual velocity the November meteors en tea* the earth's atmosphere on any given assumption 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 son.

And thus it became possible to determine, on each of the above assumptions, what is the actual path traversed by the November meteors. But than, 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 rJeo.

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

Now astronomers might hove waited for many years before they would have been able to verify the occurrence of such a change—but, fortunately, we have records of the occurrence of the November shower in long past years; ко 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 position was not accounted for on any of the assumptions mentioned above. It became clear that the meteors are subject to disturbing attractions of a more effective character. In other words, it seemed as though the meteors must travel out into regions where the giant planets, Jupiter and Saturn, or even Uranus and Neptune, are capable of exerting more influence than they can exert on bodies travelling always near the earth's orbit.

It was an obvious consideration that, this being so, the real period of the meteors is, probably, that same period—33} years or so—which separates the recurrence of marked meteoric displays belonging to this system. For with a period of 33} years, a body which along one part of its path crosses the earth's orbit, would along the opposite path be far out in space, even beyond the orbit of distant Uranus.

The calculation of the motions of bodies travelling in such orbits is by no means an easy matter. Astronomers, though they often have to deal with the motions of bodies in very eccentric orbits, yet are seldom required to follow those bodies along the whole course of such orbits, or to trace out those processes of change which affect the position and figure of the paths of such bodies.

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 affecting the meteor's orbit are most satisfactorily accounted for on the supposition that the meteors really travel out into space along the eccentric 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.

The Italian astronomer Schiaparelli had been led to notice that the bright comet of 18ti2 passed close by the earth's orbit at a point lying very near the spot where she encounters the August meteors. Now that comet travelled in a very eccentric path, having a period variously estimated at from 126 to 145 years, but undoubtedly very long. It occurred to Schiaparelli to inquire whether, on the supposition that the August meteors travel on au 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 real period ia somewhat ton-pr.

the meteors and the comet. Now it appeared that the path of the meteor« (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 favours the belief that the coincidence is not accidental, but that, in some way (even now not fully understood), the meteor system and the comet are associated together.

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.

But no bright comets were found which could be associated with the November meteors, and at first the search for faint ones was unsuccessful. By one of those extraordinary coincidences, however, with which the history of science has familiarized us, a telescopic comet had but я few months before been detected by Tempel, the orbit of which (only calculated a few week before Adams completed his labours) was found t to correspond very closely—or rather, in effect, exactly—with the track of the November meteors.

Thus quite a new light was thrown upon the nature of these wonderful meteor systems. I pass over the later researches, which have shown that other well-known periodical meteor systems are either associated with known comets or travel in orbits demonstrably eccentric. The two instances above dealt with are quite sufficient to establish the important conclusion that the meteor systems are not in any way limited to the neighbourhood of the earth's orbit, but extend far out into space along orbits of the most eccentric figure.

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.

WE may now attempt the examination of our piece of cuttlebone, or as the learned call it, Sepiostaire. We will commence by dividing the "bone" into halves across the axis with u 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 laminre of excessive delicacy, which wind in sad about, reflecting upon themselves at intervals, so as to form a better support for the plates. Many have described these sinuous lamüue as "pillars," but their true character is easily discoverable if we make a careful horizontal section, removing the "calcareous plate," BO 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 eepiostoire would surprise the novice. The outer horny case of the bone requires a different treatment, and would hardly be adapted to the hands of two beginner. Before we leave, for a time at least, the sea

* It is not to be therefore understood that the coincidence 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 lonleee very many and vary oxaot observa lions have been made, or unies» 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.

I By Dr. Peters of Altena.

side, we «ill 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, &<■.). found on all our coasts furnish very good objects for the microscope of moderate power—and be it understood that I »hall speak of nothing which a £3 3s. instrument win not show well, with the exception of polarizing, which would entail £1 10s. more. These must be carefully washed with fresh water, and then mounted either as "opaques," or in section as "transparents," in balsam. I have one slide—a Flustra foliácea, found at Hornsea, Yorks—which comes out grandly by polarized light. This Flustra is composed of small oblong cells; the base memI mine 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.

A parasitic Flustra, common on sea weeds, also furnishes a very pretty object for the inch objective. Of corallines, such as the "sickle," our shore» commonly have an abundance; and these well mounted as opaques arc 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, hut 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 toler

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.

If an animal whilst plunged under water, is prevented from coming to the surface to breathe, at the end of a minute and a half it will appear to be quite dead, and the jaws will be firmly contracted. By keeping the month open, and causing movements to be executed similar to those which arc produced in the act of respiration, the animal will recover life in proportion as the air penetrates into the lungs.

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 Bubject 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

ably well known to most of our readers; yet oblongata, and immediately the contraction dis

probably few of them have paid it the attention that it deserves. Let us take one from our miscellaneous gatherings and give it a look over. The "Aristotle's lantern," being the jaws of the creature, may first attract our notice. The teeth which compose the jaw are five in number, and euch "tooth has somewhat the form of that of the front of a rodent, save that its concave side is strengthened by a projecting keel, so that a transverse section presents the appearance of ' I .'" The tooth itself is composed of carbonate of lime, and is in structure essentially the вате as the shell; the keel is composed of "cylindrical rods of carbonate of lime, having club-shaped extremities," and the "concave side of the tooth is coated with a firmer layer," which some have likened to the "enamel" of the teeth of vertébrate. These teeth are furnished with delicate serrations, visible by the aid 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.

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appeared.

The attempts to recover a drowned man from the state of apparent death ought to be so much the more persevering as the fact of the persistence of the contraction of the jaws is almost tantamount to a certainty of seeing them crowned with success. If, unfortunately, life is extinct, we have a sure sign of the inutility of any attempt at resuscitation in the spontaneous unclosing of the teeth and the opening of the mouth.

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ÍT 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 eign 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 but not breathe, and when we come out of the water we still preserve for a long time the sensation of contraction and constriction of the throat. Let any cause or agent intervene to threaten the respiratory function in its physiological conditions, the sensitive disturbance which the pneumogastric nerve receives from it instantly causes the motor nerves—the spinal, hypoglossal, and the laryngeal nerves—to enter into action, and imme

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SCIENCE FOB THE YOUNG.

Вт The Rev. E. Kebnan, Cloxgowes College.

(Continued from page 339.)

ArPENDDt VI.

Polyqon Ok Forces.

IN determining by composition the equilibrium of any system of forces, there is formed a polygon, which begins with one of the forces, continuée by parallels equal to the other forces R in order, and is closed by the

I »■ ' e- » final resultant. In Fig. 71, pi pa ps pi psi are a number

of forces acting on the point X. Combining P1 and PJ, there is produced the side Pi A, parallel to P». Continuing the combinations as in Law VI., there is produced: 9 ABparalloltoP\BCparallel to P», С D parallel to P6, and D X closes the polygon. For equilibrium R X, a force equal and opposite to С X, is added. Therefore, this system of forces in equilibrium is represented by the polygon P А В С D X. Its sides being equal and 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 maybe 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 peint if they be disposed in order parallel to the sides which represent their magnitudes."

In the polygon A, Fig. 72, the sides are to one and other as 4, 2, 5,3, 1. This polygon (of wood) being clamped on to the table of the apparatus in Fig. 64, cords are disposed, Fig. 72 (from a ring, D, held by a pin to the wood), parallel to the sides of the polygon, by means of the pulleys, on the frame.» Weights proportional, as 4,

* The frame is omitted in the present figure, and the pulleys яге nearer than they should be ii «tu- whole appa ratus were glveu.

1, 3, 5. 2, are hung to the cords which are parallel to the sides, 4, 2, Arc. ; • when the last weight is hooked on, the pin may be withdrawn: the ring will not move. The student may exercise himself with this apparatus by taking a number of force« (weights) at random. Let them settle into equilibrium. Now

draw a polygon with sides parallel (in order) to the forces. Measure the sides of the polygon; their lengths will be found proportional to one aad other as the forces to which they are parallel. For the truth of the polygon of forces, it is not necessary that all the forces act in the same plane. This point may be said to belong more strictly to the next application.

Sob- Appendix.
Strain.Disposition Of Fobces.

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.

Appendix VII.
"parallelopiped Of Forces."

As a polygon represents the equilibrium of a number of forces in (more or less) the same plane, so a solid figure with its diagonal represents a number of forces in eeveral planes. The solid figure thus built upon the forces is called the "Parallelopiped of Forces." The three sides of Fig. 73 are sufficient to pve a good general notion of this important theorem. The 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, XX—shows the resultant. Add the force R, equal and opposite to the diagonal—the body at X is in equilU)rium.t

Sub-Appendix I.
Practical Questions.

Some interesting facts, and some most important matters of every day utility, depend upon the principle contained in the parallelopiped of forces. Were the subject not too difficult, these practical questions should be studied separately. For the present little more than the indication of them can be given. I. Bellringers.—Large heavy bells require a number of men to make them swing. To one large rope coming r i fil v.' from the handle of the bell aw

\ joined a set of smaller ropes.

Fig. 74ao. How the men should stand, how pull, where the stronger, where the weaker should be placed, &c, can he all calculated by the paraUelopiped of forces. II. Ships' rigging.—The general strain being known, it can be fairly calculated where the greatesi strength must be in the rigging, how tho various stays should be placed, &c. On the contrary, when, in case of storm, it may be required to "cut away," principles of calculation will show where to cut, that the source of danger be removed with all speed. HI. Moorings.—The safety of all floating bodies,

* The figures oí tie vieiahU show the Unes to which the torces are parallel. Tim«, 1 shows that the Uno («( is parallel to the sido of which the length is ont, etc. л.

t Frames of any solid figure, acut« angle, 4c. *c, aiay be used as the rectangular frame oí Fig. 78.

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ships' batteries, lights, &c., will depend npon 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 eoncmrent forces are concerned, can be calculated with great exactitude by the parallelopiped of forces.

. Süb-Appendix II. Insect Strength. Some time ago (1866) Mr. Felix Plateau published in the Bulletin de l'Académie Belgique a most interesting series of papers on the strength of insects compared with that of higher animals.* In this comparison of weight to work, Mr. Plateau found that while a horse can only do work equal to two-thirde 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 multi plication of feet, often armed with claws—curved «laws—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 hammer, Fig. 75, the force must act along the line A B, the axis of the nail. Should it strike along А С the force is decomposed, part goes along A C, part along A B. Hence the endeavour to drive a crooked nail is a great waete 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 deforces. The force of the hammer is shown in direction and intensity by the line A B, Fig. 76. That force may be decomposed into two; say one at right angles to the axis (of the nail) a 6, and another along the axis a b. Completing the parallelogram

Les Mondes, vol. i. p. 86, and vol. iv. p. 81.

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composition of

MECHANICAL MOVEMENTS.

the relative strength of the forces is seen. The effect of a с 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 weD fixed e g takes effect; if the wood can resist, с h has some small effect in sinking the point further. Many other possible decompositions of А В would show greater or less force, tending to bend or displace the nail.

ArrENDix IX.
Ropes, Chains, Etc.

The ntility of every sort of cord, rope, wire, chain, Arc, from the finest to the most massive, arises from their being able to offer an equal and opposite force to force brought to act upon them. It is " tenacity" which gives them this power up to a certain point.

Thus far the applications of leseer 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 is. II.—What is the principle of its action. III.—The conditions of equilibrium, established when possible by mathematical reasoning and formuhe. 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 J 1 Q Q Contrivance for polishing lenses and bodies JLt/di of spherical form. The polishing material 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 some parts of surface of the lens or other body.

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.

195. Four-way cock, used many years ago on steam engines to admit and exhaust steam from the cylinder. The two positions represented ore produced by a quarter turn of the plug. Supposing

* Extracted from я compilation by Mr. H. T. Bbowk, j Editor of the "American Artisan.'

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 und lever escape ment for watches. The lever is so applied in «inbinatiou 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 suid wheel.

197. Continuous circular into intermittent rev 1 tilinear reciprocating. A motion used on several 1 sewing machines for driving the shuttle. Same

motion applied to three-revolution cylinder printingpresses. 1 198. Continuous circular motion into intermiti tent 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

I in two parts, one end of each is provided with swivel, nut, 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 а second bar, В (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 oscillating in opposite directions, for the purpose of counteracting the effect of any sudden jar upon н и iik'li 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 Unes lay two of the ndes 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 y ts, will describe the arc by means of pencil in' 'gle of the crossing edges of the sloping rule?

204. Another cyclograph. Th»1 -bed bar is made half the depth at the < . is at the middle, and is formed so . uuter edge coincides with a true circular в wnen bent to its greatest extent. Three points in the required an'

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being given, the bar is bent to them by means of the 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 ou one focns as я 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 Imtween to permit height to reach vertex when ride coincides with centre line. A pcncU held in bight, and kept close to rule while latter is moved from centre Une, describes one-half of parabola; the rule is then reversed for the other hau'.

20(5. Mechanical means of describing parabolas, the base, altitude, focns, and directrix being given. Lay straight edge with near side coinciding with directrix, and square with stock against the saine, 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, anil 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; chieüy used in perspective. Upper or draw.ng 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 tobe incouveuieut to produce the convergent lines until they intersect, even temporarily, for tùe purpose of setting the instrument as Bhown. a corresponding convergence may be found between them by drawing a line parallel to and inward from each.

(To he continued.)

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IT is only of late years that the laws of motion have been fully comprehended. No doubt it has been known since the time of Newton that there can be no action without reaction; or, in other words, if we define momentum to be the product of the miss of a moving body into its velocity of motion, then whenever this is generated in one direction an equal amount is simultaneously generated in the opposite direction, and whenever it is destroyed in one direction an equal amount is simultaneously destroyerl in the opposite direction. Thi:s the recoil of a gim is the appropriate reaction to ti e forward motion oí the ballet, anil the ascent of u rocket to the dowurush oi heated gis from its orifice; and in other cases where the action of the principle is not so apparent, its truth had notwithstanding been universally admitted.

It has, for instance, been perfectly well understood for the last SOI) years that if a rock be detached from the top of a precipice 144 ft. high it will reach the earth with the velocity of % ft. in a second, while the earth will in return move up to meet it, if not with the some velocity yet with the same momentum. But inasmuch as the шяхв of the earth is very great compared with that of the rock, so the velocity of the former most be very small compared with that of the latter, in OTder that the momentum or product of mass into velocity may be the same for both. In fact, in this case, the velocity of the earth is quite insensible and may be disregarded.

The old conception of the laws of motion was tlrae sufiicient to reprenant what takes place when the rock is in the act of traversing the air to meet tire earth; but, en the other hand, the true physical concomitants »f the crash which takes place when the two bodies have come together were entirely ignored. They met, their momentum was cancelled—that was euougli for the old hypothesis.

So, when H hammer descends npou an anvil, it was considered enough to believe that the blow was stopped by the anvil; or when я 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 alinde to the names of those distinguished men who have come prominently forward as the champions of a jneter conception of things; but in the mean time let us consider vomo of Нюм inllnences whuú 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. mast yet in some sense perform work in order to live. Gra

• By li.vi.iui u Stbwabt, tu Nature.

dually, and by very slow steps, the true nature of work came to be understood. It was seen, for instance, that it involved a much less expenditure of energy for a man to carry в pound weight along a level road than to carry it an eqnal 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.

Thus, if we raise a pound weight one foot high against the force of gravity wo 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 tliis 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 inUt the intensity of lliat force trill 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 first place it does not mean force.

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

the word energy is meant the рогеег of doing morí; 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.

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

The analogy which we shall venture to institute is between the social and the physical world, in the hope that those who aie more familiar with the former than with the latter may be led to perceive clearly what is meant by the word energy in a strictly physical sense. Energy in the social world i-i well understood. When aman pursues his course, undaunted by opposition and unappalled by obstacles, he is said to be a very energetic man.

By his energy is meant the power which he possesses of overcoming obstacles; and the amount of this energy is measured (in the loose way in which we measure such things) by the amount of obstacles which he can overcome—the amount of work which he can do. Such a man may in truth be regarded as a social cannon ball. By means of his energy of character he will scatter the ranks of his opponents and demolish their ramparts. Nevertheless, a man of this kind will sometimes be defeated by an opponent who does not possess a tithe of his personal energy. Now, why is this? A reply to this question will, if we do not mistake, exhibit in a striking manlier the likeness that existe between the social and the physical world. The reason is that, although his opponent may be deficient in personal energy, yet he may possess more than an equivalent in the high position which he occupies, and it is simply this position that enables him to combat successfully with a man of much greater personal energy than himself. If two men throw stones at one another, one of whom stands A4 the top of a house and the other at the bottom, the man at the top of the house has evidently the advantage.

So, in like manner, if two men of equal personal energy contend together, the one who has the highest social position has the best chance of succeeding. For this high position means energy under another form. It means that at some remote period a vast amount of personal energy was expended iu raising the family into this high position. The founder of the family liad, doubtless, gTeater energy tlian most of his fellows, and spent it in raising himself and his family into a position of advantage. The personal element muy have long since disappeared from the family, but not before it liad 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 вес that in the social world we have what may justly be termed two kinds of energy, namely :—

1. Actual or personal energy.

2. Energy derived from position.
Let us now again turn to the physical world. In

this, ns iu the soda iworld, 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 lie shot upwards with great velocity, it may be said to have in it a great deal of actual energy, because

it has the power of doing useful work or of over coming up to a great height the obstacle interposée' 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 <i во with a gradually decreasing Telocity, until at tue summit of its flight «il the actual energy with which it started will have been spent in raising it against the force of gravity to this elevated position. It is now moving with no velocity—just, in fact, lwginniug to turn—and we may suppose it to 1л caught and lodged upon the top of я house. Here, then, it remains at rest, without the slightest tendency to motion of any kind, and we ore led tu ask what has become of the energy with which it began its flight? Has this «nergy disappeared from the universe without leaving behind it any eqaiva lent 1 Is it lost for ever, and utterly wasted? But the answer to this question must be reserved ft* another article.

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ON THE RELATIONS BETWEEN BODY AND MIND.*

(Concluded from page 342.)

THE different forms of insanity that occur in young children—as all forms of it except general paralysis may do—are almost always traceable to nervous disease in the preceding generation, a neuropathic condition being really the essential element in their causation. The eases of acute mania in children of a few weeks or a few years old which have been described might more properly ht 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 acete mania, occurring usually in connection with chorea or epilepsy, and presenting the symptoms, if I may so express it. of s 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 imliceility, is common enough in chores, and in some cases there is violent delirium; but, 1*sides these cases, there are others in which, without choreic disorder of movements, there is a choreic mania: it is an active delirium of ideas which is the counterpart of the asnal delirium of movements, and its automatic character and h- marked incoherence are striking enough to an ordiuarv observer. Hallucinations of the special senses, and loss or perversion of general sensibility, usnall.v accompany the delirium, the disorder affecting tin centres of special and general sensation, as well as the mind-centres.

Between this choreic mania and epileptic mania there are intermediate conditions partaking more or less of the character of one or the other—hybrid forms of a cataleptic nature. The child will lie for hours or days ¡и я seeming ecstasy or trance, with its limbs rigid or fixed iu я strange posture There may be apparent insensibility to impressions, while at other times vogue answers are given, or there is a sodden bursting out into wild shrieks or incoherent raving. If this be of a religious kind, the chad 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 the other hand, into true epileptic seizures, or alter uate with them.

In children, as in adults, a Irrief attack of violent mania, a genuine mania transitorio, may precede, or follow, or take the place of ян epileptic fit; in the latter case being a masked epilepsy. Children of three or four years of age are sometimes seized with attacks of violent shrieking, desperate stubbornes». or furious rage, when they bite, tear, kick, and da all the destruction they can; these seizures, which are a sort of vicarious epilepsy, come on periodi cally, and may either pass in the course of n few months into regular epilepsy. or may alternate with it. Older children have perpetrated crimes of a savnge and determined nature—incendiarisni. and even murder—under the influence of similar attacks of transitory fury, followed or not by epileptic con vulsions. It is of the utmost importance to realm' the deep effect which the epileptic neurosis may have on the moral character, and to keep in mind the possibility of its existence when a savage, apparently motiveless, and unaccountable crime h^ been committed. A single epileptic seizure ha. been known te change entirely the moral choract.' г rendering a child rude, vicious, and perverse, wh was hitherto gentle, amiable, and tractable. Ni one who has seen it can fail to have been stmci with the great and abrupt change in moral character which takes place in the asylum epileptic immediately before the recurrence of his fits: ill »he intervals between them he is often an amiable, obliging, and industrions being, but when they impend he becomes, sullen, morose, and most dangerous to meddle with. Not an attendant but can then foretell that he is going to have hie fits, »s

* Twolecturee delivered «t the Royal College of Пит sic ¡uns íh 1870. Bv HnitKï Macdsleï, M.D., F.H.C.F. Processor óf "STedlcsl Jurlsprtnttnie In UniTersit I College, Londor.

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confidently oliuostae he can foretell that the sun will rise next day. Morel has made the interesting observation« which is certainly well founded, that the epileptic neurosis may exist for a considerable period in an undeveloped or masked form, showing itself, not by íonvulsions, but by periodic attacks of mania, tit fty manifestations of extreme moral perversion, v, lai;h are apt to be thought wilful viciousness. But they are not—no moral influence will touch them: they depend upon a morbid physical condition, which can only have a physical cure; and they get : ■ ir explanation, and indeed justification, afterwards, 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 distinguish it from one form of the insane neurosis. The difficulty of doing so is made greater, inasmuch ам epilepsy in the parent may engender the insane neurosis in the child, and insanity in the parent the 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 »patmullica. Take, for example, a case which is one of a. close—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 on entry in his diary, " killed the 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, bRd 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 the 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 farther affected than in having- lost power to control, or having become the slave of, the morbid and convolsive 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 к 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 re f-ponsibility which dooms an insane person of this cines 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 epiléptica —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. Skoe records an instructive example in one of hie annual reports. The feeling began at 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 history and feelings. In other cases a feeling of vertigo, a trembling, and a vague dread of something fearful being about to happen, resembling the vertigo and momentary vague despair of one variety of the epileptic aura, precede the attack. Indeed, whenever a murder hag been committed suddenly, without premeditation, without malice, without mo tive, openly, and in a way quite different from to о way in which murders are commonly done, we ought to look carefully for evidence of previous epilepsy, and, should there have been no epileptic

fits, for evidence of an aura epiléptica 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.

In bringing this lecture to on end, I may fitly point out how entirely thus far the observation of the phenomena of defective and disordered mind proves their essential dependence on defective and disordered brain, and how closely they are related to some other disordered nervous functions. The insane neurosis which the child inherits in consequence of its parent's insanity is as surely a defect of physical nature as is the epileptic neurosis to 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 шоу 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 con 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 s mental science ; and it is because metaphyseal mental philosophy has taken no notice whatever el them —because it is bound by the principle of itse\istenee as a philosophy to ignore them—that, notwithstanding the labour bestowed on it, it has borne no fruits —that, as Bacon said of it, "not only what was asserted «nee is asserted still, but what were questions once ore questions still, and, instead of being resolved by discussion, are only fixed and fed."

DIAMOND ROCKBOKING MACHINE AT THE CBOESOB SLATE QUARRIES& {nimtraUd at page 878.) ДТТТ5 recently had an opportunity of visiting the VV works of the Croesor United Slate Company'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

S eater speed than could possibly be got by hand bour, has induced the company to call in the aid of the diamond boring machine, with the proprietors of which, Captain Beaumont, R.E., and Mr. C. Appleby, they have entered into a contract.

Amongst the various propositions which have been brought into notice for machine tunnelling, one of the most courageous and successful is that in which a coarse cheap kind of diamond is used to form the head of the cutting tool. Since the introduction of the system, it has, of course, worked its way through many stages before it arrived at being а 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

the Croesor mountain, and runs downwards at an angle of -10° 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 quarr/. 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 horizontal base, a a, coupled by four links with the motor (B)—on air-engine—behind it. Within the base, a к, a horizontal shaft rotates, receiving its motion through a pulley and belt from the fly-wheel of the engine. The vertical columns, r, c1, have each a shaft revolving in their interior for giving motion to the boring tools, il, a1. 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 horizontal shaft, and being held in place by suitable bridles.

Each upright shaft has two (sometimes three) similar bevel wheels, each engaging with the corresponding wheel of a boring tool. With this arrange nient 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 t'j о 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 boring tool is fixed at the end of a long screw, a nut upon which revolves with it, being connected with the driving gear by о friction clutch. The wheel which imparts direct rotation to the drill has one tooth more than that which presses against the nut. A differential motion is thereby obtained, which causes the boring tool to advance a certain distance with every revolution, unless the. resistance which it meets in the rock becomes too great, when the clutch slips and prevents breaking the tool.

To «void 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 thoy 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. The motor, B, attached to the boring machine, consists of an engine worked by compressed air, which is forced down the shaft through a gospipe, 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 hold. This causes the vertical columns, с, с1, 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 supplied by a turbine in the valley below; and this turbine is worked by a head of water conducted to it from a tank on the side of the opposite hill. The tank is fed from B small mountain lake ,which is perched among the hills high above the sea level, and which hoe been dammed up and provided with a sluice for the purpose. The tank into which the lake-water flows is H.'iOft. above the turbine, with which it is connected by a fin. castiron pipe. The turbine works a double action airpump, and the compressed air is conducted up to the mouth of the shaft through a din. 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 1югег, it pumps water out of the shaft, and it Starts the hanling-up drum.

The rope by which the loaded wagons are drawn up out of the shaft is worked on the tail-end' syetom npon 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 connect' *. with a mountain stream which fills it. When \ its weight in running down its incline is r t to draw up the full

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