light by friction, or by the traditional flint and steel, up to the present time. Lord Bacon in his writings spoke of the process of the smiths of his day in producing light by hammering a small iron rod upon the anvil until it became so heated that when thrust into a bunch of shavings, the shavings became ignited. It was not, however, said Dr. Paul, till 1798, that Count Rumford, a Scotchman, who had been much engaged in military matters, and particularly in the manufacture of cannon, observed that heat was given off in the process of boring cannon, and succeeded in inventing an apparatus by which he was enabled to measure the quantity of heat given off by a certain amount of work. In 1842, Mayer, a German introduced the term "mechanical equivalent of heat ;" and a year later, Joule, of Manchester, made a return of the numerical value of the ratio between heat and mechanical energy, by which quintities of heat could now be expressed in terms of units of work, and in other ways. Dr. Paul then made a few observations relative to the way in which fuel was burnt in the production of steam, and in which the steam was disposed of, and the results obtained. The application of heat to water for the purpose of producing steam was daily illustrated by the use of the kettle. Reversing the question, he spoke of the method of taking heat out of water so as to produce ice, a method not used to any great extent in this country. In the boiling of water, the heat generated by fire was transmitted to the water, raising its temperature to 112 degrees, and then converting the liquid into vapour or steam. Precisely in the same way ice was melted by applying heat to it, and both changes required certain definite amounts of heat. The same quantity of heat that would convert 15lb. of wa er from the boiling point into steam would heat 801b. of water from the freezing to the boiling point, and would melt 1021b. of ice into water, which, after being melted, would be at a temperature of 32 degrees. The production of cold was an operation to which attention had lately been paid, and the nature of the work to be done was very much the same as that required for producing steam. To produce ice we must take heat out of water; and the way this must be done was to find a substance which would absorb the heat from the water at a temperature at which ice could be formed. Ammonia, alcohol, or ether would do, although the latter would probably be the most suitable. Dr. Paul concluded his lecture by a reference to the other modes now in use for producing ice. The perpendicularly between the thumb and fore- a set of individual small pictures, utterly disfinger, at arm's length or nearly so, and, shutting united; and disunion ought not to be ever one eye, notice the proportional heights of trees, pleasant to the eye or to the mind. It is not lines of building, and specially the width of enough, therefore, that each object have its own horizontal planes; for the latter are sure to light and shade, but there must be always some cause no little surprise; they are probably less further general light and shade to unite the subthan half the width they were thought to be, and jects into one; and it is here that the accoman inch in length of the pencil thus held will plished artist revels at will-now causing unity measure some miles of a level country. This is and concord by breadih of light, now by a skil illustrated in Fig. 19, where the space a, b, on the fully thrown breadth of shade, now by cunning repetition of form, now by a cast shadow. In a thousand ways, taught by ever-growing experience, he effects with ease what a beginner cannot do by days of studied toil. Yet still something may be done, even in the earliest attempts, and this union and unity has always to be the aim of any one and every one who desires to become a proficient. The great secret is not to let the lights of the pieture be scattered about here and there, nor the shadows either, but to connect these by secondary lights and shadows. This will give to the eye, and thence to the mind, a sense of rest, and thus produce a pleasing impencil, will evidently measure c, d, on the land- pression; but when light is scattered about all scape. It would be the same if the pencil were over the picture, the eye is drawn from one part replaced by a sheet of glass, and this is just to another, resting upon none-for, be it ob of small size, yet are able to view an extended lights, and thence passes to the shadows. Morewhat occurs when we look out of a window-pane served, the eye is always first attracted by the from this experiment, which should be tried at focus of brilliancy, as in a shadow one point scene before us. The student may further learn over, in a broad light there should always be a all times and in various ways, the vast difficulty should be deeper than the rest. Howard, in his to be encountered in giving the appearance of an "Sketcher's Manual," gives certain rules upon extended landscape in a picture of such narrow the above particulars of chiaroscuro, but they dimensions. spective, requiring a practised hand, and hence rather to send the student to nature than to set It is a question of aerial per are too artificial for our purpose, as we desire not even to be attempted until some skill in the forth definite rules of art. delineation of simpler subjects has been attained. relating as they do more to composition than to The latter, indeed, With regard to the size of picture or quantity of sketching, would be of no use to the beginner, landscape that may be introduced, the general however clearly laid down; and to compose a rule is to take such an extent of view as can be picture requires a thorough acquaintance with included in an angle of 60°, which is as much as Nature in all her ever-varying aspects, and may the eye can compass without an effort. In an be at once considered as the most advanced study open country, and for distant objects, this will of the most thoroughly-taught artist. give a wide field; but for foreground subjects, it reader, therefore, may rest satisfied that he will will of course include less. necessary for the sketcher to know much about ful studies from Nature, than by any such It is not, however, please himself and his friends far more by carethe optical limit of vision. Let him take what attempts at high art. It may naturally be exhe can see comfortably at a glance, and he will pected that we say something of trees, and the not be far wrong; and the same rule is ap- method of treating them. First there is the plicable with respect to the foreground. If we perspective to be attended to, by which the upper look at what is close at our feet, it is plain part will curve downwards, the lower part upthat we cannot at the same time see what is wards; that on a level with the eye will be itself distant; but if we make things at a moderate horizontal. Thus we shall see underneath the distance our pictorial foreground, we can include branches, and under the several masses or layers a good deal beyond it. The width of the picture of foliage, until we come to a level with the will be generally far more limited than its dis- horizontal line. Below this we shall look down tance. Hold up the sketch-block nearly at arm's upon the upper convex side of the foliage. Next, length, and notice what it hides, and this may it may be well to note the great variety in the generally be taken as the limits of the sketch. branching of trees, which we have at this time Try another experiment. Bring the sketch- of year every facility for studying; and as we WH HEN a novice first sits down before the block gradually nearer to the eye, and observe can sit indoors, and sketch from the windows, how much more it covers. scene which he desires to depict upon intend to hold your picture so close when finished sketched when bare of leaves, and afterwards But you do not such study need not be passed by. A tree paper or canvas, his usual difficulty is to deter- for inspection, and you should, therefore, bold from the same spot when clothed in summer vermine how much of the scene he ought to your sketching-block further from you, because dure, will teach more than a dozen pages, delineate, and how near his own position the perspective teaches us to delineate a given sub- although illustrated. In Fig. 20, however, is picture ought to terminate. He also is usually ject (upon paper) as we should see it if that paper sketched the upper part of an aspen, in which rather doubtful as to whether the lines of yon distance from the eye. were transparent, and held at a certain given the branches have scarcely any perceptible angu cottage roof ought to tend upwards or down- take this distance as nearly an arm's length. To character. In Fig. 21 we have, on the other Practically, we may larity, giving a wavy, exquisitely elegant wards. In fact, he somewhat resembles the get thoroughly hold of the principles involved, it hand, marked angularity, as in the oak and the Englishman who, with a fair amount of school is a good plan to sketch some simple object-a thorn. In Fig. 22, which represents a bit of ash French in his head, first set his foot upon con- and from different distances; stand above it, and the ends of the boughs nearly always given brick, for instance-from all sorts of positions stem, there is a medium between these extremes, tinental soil. The language sounds as strange to on a level with its upper surface; below, on one up, as in the sketch. bis ears, and is as incomprehensible, as that of side, opposite one corner, &c. Stand near and far examples of the gene al way in which leafage is the Ojibbeway Indians, and is not what he ex- off, and draw what you see, and no more. A treated in a sketch, with the larger lights on the peeted. The art student, similarly, finds the white brick in a half light will teach you much, upper surface of the layers, beneath which the view before him by no means amenable to the and when you begin to colour, a red brick, backed deepest shadows are generally found. laws of perspective, which he fancied he had by green leaves, will give you a good lesson. If finished picture foliage is, of course, much more come right by-and-by: and as the sketcher gets not, you had better not draw at all), do all as aspect is rapidly blotted in or pencilled. IndiNever mind; it will all you wish to draw well, moreover (and if you do elaborated; in a sketch from nature, the general accustomed to view scenery with the eye of an thoroughly and truly as you can. artist, the several subjects will fall into their subjects, but work them out on the spot. It is close at hand, and distance is expressed whether Take simple vidual leaves can only belong to such trees as are proper place, and there will be little difficulty in impossible to finish at home; your memory is by brush or pencil by avoiding detail, and giving sketching them correctly. outdoor practice is increased, the indoor theories sketcher will at first be much dis-arisfied with the which in nature become greyer as they recede Moreover, as the far too untrustworthy. In all probability the more and more indistinctness to the masses, will become more comprehensible, and errors in general effect of his pictures, which will look from the eye. These details should be studied drawing will gradually diminish. Remembering tame and uninteresting, even though the several constantly. The sketcher should, whenever he always that lines of really equal height diminish details may have been carefully drawn and takes a walk, note the aspect of the same subin proportion to their distance from the eye, shaded. there will be little difficulty in ascertaining which doubt the ability of any pupil of mine to become ingly ugly), and vegetation generally, as they Personally, I should be inclined to jects-e. g., trees, hedgerows (which are exceedway the roofs of houses and similar horizontal an artist if he were not thus dissatisfied. His appear at different distances. Lines tend. SKETCHING FROM NATURE-III. understood so well. In Figs. 23 and 24 are given in A tree close to it greatly simplifies the task of sketching to rule pectation that several objects carefully drawn individual leaves: note, however, that no two But there can be no question that disappointment probably results from the ex-him will show in its nearest and outside sprays line across the drawing, at the height of the upon one sheet of paper will, as a matter of are alike, partly because they lie in different Te, and to mark upon it the position of the course, make a picture pleasing to the eye. This, planes, and partly be ause they overlap and ye, or point of view, and also the vanishing however, is by no means necessarily the case. points (if such are needed). Then hold a pencil. They may and will for a time constitute rather remote displays masses-layers of flinge v interfere with each other A tree rather n little work of that name, compiled by Mr. Henry 1. A mode of obtaining an egg-shaped elliptical movement. deep shadows between, the upper masses shut- between them forming a steam chamber I. B B ting out the light of the sun from below them. are revolving shelves, and C is a self-acting screw Still further off a tree is a mass of gradated, for feeding the grains from the hopper D into the grey shadow, yet even then the general form machine. A connection is made with the steam suggests the kind of tree. In buildings, again, boiler by means of the pipe E, through which the details become more and more indistinct as we jacket I is supplied with steam. The condensed go further from them. Doors and windows fade steam escapes at F. G is the exit for the dried into oblong patches of shade (unless the sun grains, whilst H is a ventilating flue for carrying 2. A movement used in silk machinery to On the shine brightly upon the glass), yet still there off the vapour arising from the grains or other will be always a suggestion, so to speak, of substances being operated upon. The action of guide the silk on to spools or bobbins. detail. It is a mistake to make the distance the machine is very simple:-The wet grains are back of a disc or bevel-gear is secured a screw with a tappet-wheel at one extremity. On each always paler than the foreground. Very gener- fed in through the hopper, and are gradually carally the middle distance is the darkest part of ried to the other end of the machine by the revolution of the disc the tappet-wheel comes in the picture. It is delicacy of treatment, not revolving shelves, where they are delivered dry. contact with a pin or tappet, and thus receives an paleness, that gives distance, and the contrast of The rate at which delivery takes place is of course intermittent rotary movement. A wrist secured a vigorously expressed foreground. Our allotted governed by the degree of dryness required, and to a nut on the screw enters and works in a slotted space is now filled, but it is hoped that even is regulated by the working speed of the engine bar at the end of the rod which guides the silk on this slight sketch may assist those who intend to which drives the machine. The degree of heat the bobbins. Each revolution of the disc varies the length of stroke of the guide-rod, as the devote their spare time in the ensuing summer imparted is also under perfect control. to the most delightful study possible-a study machines at Messrs. Milburn's works are driven tappet wheel on the end of the screw turns the screw is therefore changed. that always repays our labour a thousand-fold. by a 10-horse power engine, steam to which-and Screw with it, and the position of the nut on the The writer strongly recommends the brush and sepia as a substitute for pencil or pen and ink, as being, after a little practice, much more manageable, and affording the most rapid method of work. For passing effects of light and shade, such as we specially see on cloudy, threatening days, when momen ary gleams of sunlight flash across the scene, th s medium is perfect. But whether by pen, pencil, or brush, let nature teach, and don't try to teach nature. J. L. DESICCATING GRAINS. (Illustrated on page 13.) HE fact that the spent grains from our The to the dessicating machines-is supplied from a steam space Another form of this apparatus has just been completed by Messrs. Milburn, who have combined the drying machine with a portable steam engine. This arrangement is seen in perspective at Fig. 3 of our engraving, Fig. 4 being a part MILBURN AND CO.'S APPARATUS FOR cross section and front end view. Here A is the in connection with the water space below; in other words, this is the boiler of the engine. The revolving shelves are seen at B; C is flue from the furnace to the funnel, in the leading for the dried material. The operation of drying is the same as in the machine we have previously described, the difference being only in the construction of the apparatus, the one being fixed and driven by an independent engine, the other being portable and having its driving power attached to it and transported with it. This machine will be found very valuable to agriculturists and others for drying corn, seed, pulse, roots, &c., also for coffee planters and others, and, being mounted on wheels, it can be readily removed from place to place. Tbreweries and distilleries, when properly dried, become a valuable food for horses and all kinds of cattle has been recognised for some time past, although we believe it is only within the last few years that systematic attempts have been made to turn this knowledge to profitable account. The question of desiccating grains has received very careful attention at the hands of Messrs. Milburn and Co., of 76, Church-lane, Whitechapel, and they claim to have perfected an apparatus which successfully solves the problem they set themselves to work out. A perspective view of the machine is shown at Fig. 1 of our engraving; Fig. 2 being a vertical section through the MECHANICAL MOVEMENTS. 3. Carpenters' bench-clamp. By pushing the clamp between the jaws they are made to turn on the screws and clamp the sides. 4. A means of giving one complete revolution to the crank of an engine to each stroke of the piston. 5 and 6. Contrivance for uncoupling engines. The wrist which is fixed on one arm of the crank (not shown) will communicate motion to the arm of the crank which is represented, when the ring on the latter has its slot in the position shown in 5. But when the ring is turned to bring the slot in the position shown in 6, the wrist passes through the slot without turning the crank to which the said ring is attached. slide Cortying the cutting tool in slotting and The driving-shaft works shaping machines, &c. through an opening in a fixed disc, in which is a circular slot. At the end of the said shaft is a slotted crank. A slide fits in the slot of the crank and in the circular slot; and to the outward extremity of this slide is attached the connectingrod which works the slide carrying the cutting tool. When the driving-shaft rotates the crank is carried round, and the slide carrying the end of the connecting-rod is guided by the circular slot, which is placed eccentrically to the shaft; therefore, as the slide approaches the bottom, the length of the crank is shortened, and the speed of the connecting-rod is diminished. Contrivance for varying the speed of 8. Reversing-gear for a single engine. On raising the eccentric-rod the valve-spindle is working the upright lever, after which the eccentric-rod is let down again. The eccentric in this The dimensions of the " HE MECHANIC," a penny publication, machines are about 19ft. in length and 4ft. in TME Andy" incorporated with the released. The engine can then be reversed b ENGLISH MECHANIC, gave from week to week a series of "Mechanical Movements," from a useful diameter. A is a fixed cylinder, which consists of two boiler plate shells, the 2in. annular space case is loose upon the shaft and driven by a pro- | the eccentric, and the steam-ports will only be before the termination of the stroke, and the (To be continued.) THE EAR-ITS USES AND ABUSES. BY DR. USSHER. 44 little daughter in company with another child. Who may your friend be?" asked the father. "She is an inquaintance of mine." Poor Beethoven! You might have flooded the world with the fruits of your unrivalled genius if woman's tender suasion had drawn you out of yourself and left you untrammelled by your galling kindred. Deafness to the musician, or blindness to the painter, who can say which is the more dire 10 and 11. Diagonal catch or hand-gear used calamity? Signposts on the way to decrepitude; in large blowing and pumping engines. In 181 slackenings of speed that tell of sands nigh run the lower steam-valve and upper eduction-valve out; warning chimes of a fast-fleeting three are open, while the upper steam-valve and lower score years and ten-perhaps, a long way on this eduction-valve are shut; consequently the piston will he ascending. In the ascent of the piston-FI were asked to point out the most complex side the mark. We hear with the keenness of rod the lower handle will be struck by the pro- part of the body in the smallest space, I childhood, we feast in olfaction the glories of the jecting tappet, and, being raised, will become would indicate the human ear. It is the solitary summer flower garden freshened by a passing and lower steam valves; at the same time, the cerned in locomotion or prehension, and appa- and gone-the flowers are the same, the brightengaged by the catch and shut the upper eduction instance of bones, joints, and muscles not con- shower, but as we advance in life we find things are not what they were, pleasures are grasped upper handle being disengaged from the catch, rently beyond our control. Our senses are cor-ness of the glowing sun is none the less, the the back weight will pull the handle up and open the upper steam and lower eduction-valves, when related-each helps the other as a valuable hand- lovely quiet of a summer's eve, with its schoolthe piston will consequently descend. 11 repre- maid, recognised only too vividly as such when boy reminiscences-a far back vista-is brought from memory's treasure-house; friends gone sents the position of the catchers and handles the loss is experienced. We see people happy from our very embrace are present in imaginawhen the piston is at the top of the cylinder. In enough under the privation of one sense, but tion, and change impresses its finger on all going down, the tappet of the piston-rod strikes when the gap becomes larger, then it is an exist- things. Why should it not? There is nothing the upper handle and throws the catches and ence so blotted and blurred that comfort only perfect here. Some of us are born with decay handles to the position shown in 10. comes with the certain hope that in another world ready imprinted, a tiny spark it may be, but 12 and 13 represent a modification of 10 and all these groanings of creation will be set at rest soon fanned into giant dimensions, the unex11, the diagonal catches being superseded by two in the perfect liberty of the children of God. panded bud is nipped, and on all is inscribed quadrants. The blind man, who, from his birth, has been decay. How often comes the expression, with a 14. Link-motion valve-gear of a locomotive. deprived of the sense of the beautiful, who sees sigh, "I cannot do what I used " Two eccentrics are used for one valve, one for "men as trees walking;" the deaf mute who can friends, we once could go hand-over-hand the the forward and the other for the backward never take in the beauty of song, are lightly five-barred gate; that no longer suits us; solid movement of the engine. The extremities of the smitten compared with those who are suddenly thews and sinews are useful but not lithesome; eccentric-rods are joined to a curved slotted bereft of these luxuries of life; they will hardly we now feel that we have organs that we must bar, or, as it is termed, a link, which can be adopt Pope's saying, that "whatever is, is best." use with deference if they are to be lasting, raised or lowered by an arrangement of levers Can we read the history of Beethoven's crushing although time was, I daresay, when you and I terminating in a handle, as shown. In the slot calamity of deafness, stealthy in its approaches a myth, or, at best, the of the link is a slide and pin connected with an as the heavily-laden thunder-cloud, without feel- semblance of a reality capable of accommodating arrangement of levers terminating at the valve- ing the deepest sympathy for that will-impas- anything short of paving-stones-but pain is a stem. The link, in moving with the action of sioned nature, weird-like in its grandeur, fierce, reminder, physic is a reminder -notably that the eccentrics, carries with it the slide, and uncouth, rendered all the more taciturn by the horrid chief remembrancer, Gregory's Powder," thence motion is communicated to the valve. master malady of his life, denied the full enjoy- which chemists call a "Khabarbarate of MagSuppose the link raised so that the slide is in the ment of the very wonders he created, poor, inde-nesia"-barbarous enough in any sense, looking middle, then the link will oscillate on the pin of pendent, high-souled, he seemed at last to wrap like a compound of crabs claws prepared by the slide, and consequently the valve will be at himself within himself, preferring gloom and loving hands, and from which escape was imposrest. If the link is moved so that the slide is at solitude, to such friendships as were worth his sible, for if your sense caused you to eject the unone of its extremities, the whole throw of the acceptance? savoury morsel through your nose into the cup or eccentric connected with that extremity will be Forgotten at Vienna, where he is now adored, giver's face, a double portion in the morning was given to it, and the valve and steam-ports will be he died without the worldly consolations, Cole- your shepherd's warning." This was a reminder opened to the full, and it will only be toward the ridge has so happily touched, and quaintly ex- that your future journey through life was to be end of the stroke that they will be totally shut, crossed by ups and downs-troubles as plentiful consequently the steam will have been admitted as the sparks that fly upwards. What has all to the cylinder during almost the entire length of this to do with our senses and privileges? Much, each stroke. But if the slide is between the I opine, considering that the better you use them middle and the extremity of the slot, as shown in the longer you will enjoy them. My labours, I the figure, it receives only a part of the throw of These were written on the occasion of seeing his trust, have not been in vain in my endeavour to pressed, in the following lines: Tho' friendships differ, endless in degree, considered a stomach No, my lighten your eyes, and it will not be my fault if Man being the highest of creation, has everything for his wants fashioned in the highest perfection, a place for everything, and everything in its proper place," saves his ideas, and these tenements of his brain be occasionally lets out to queer lodgers. We will follow the same division here as in the former paper on "The Eye," considering first the external, then the inner or true ear; but first look at the temporal bone of the skull, called so because "Old Time," or Tempus, left his grey hairs thereon as a set-off against the bald vertex. In that triangular-looking portion which is the hardest in the body, was once the perfect hearing ear, there are some odd holes or so in it that used to puzzle us students when we had nothing better to do than load our brains with hard names, and devious courses of nerves, what they were related to, and what not, and what, I am rejoiced to say, I have long since forgotten, names invented to frighten one, as I thought when I came across the "mylohyoidean branch of the inferior dental of the fifth pair." Pity they didn't add some more! Now, this earbone contains an anatomical nut, one of the wonders of the body, seldom broken into unless a terrible fracture of the skull shatters it. The eye was placed in the front of the body, the van, as it were, the ear, as sentinel, does duty in the M. the auricle, or external ear, so far as you might woven babitations crowds of spiders, which formed (To be continued.) THE EARTH-ITS FIGURE AND It used to be said when your left ear was red somebody spoke well of you that I can't be certain of; but when both ears suddenly redden you may set it down, on my authority, that the parties have not paid their doctor's bill. Why one ear should be hot to tingling and the other quiescent, is one of those things we have yet to learn, unless it be that one carotid artery is larger than the other, and this may account for the common fact that one whisker is smaller than the other. Special muscles are attached to the ear which cause it to raise itself when any special message is telegraphed-not under post-office surveillance. Some people can move the ear upwards and downwards. I am favoured with that addition to my accomplishments. When the ear is outstretched, increased hearing is the result. Look at the sharp terrier, how movable his auricles are; how he fixes them forward when he smells a rat, and, with forepaws outstretched, is ready for a spring. Watch the activity of the ear in the graceful greyhound; or observe the cavalry charger with outstretched ear patient for the call to arms, eyes intent, nostrils dilated, muscles in impatient quiver, as if horse and rider were all one. When I had the misfortune to be a parish doctor, drawing the munificent stipend of £60 per By annum, more or less, and obliged to keep a horse to do the work, I used to talk to my horse as I went along, and watch his ears moving as if he understood me, and the poor beast evinced his gratitude for kindly care far more so than some of the patients. He, as a goodly Houynhym, appreciated my kindly qualities, except when IBRA passed a ball down his throat, and patted him into an appreciation of the bolus. If the power of speech had not been denied to him, he would surely have exclaimed, "Save me from my friends!" Would that we were always as ready A pretty ear is one of the special ornaments to the call of duty as those dumb creatures, -may I say vanities?-of the ladies, highly prized. and ever grateful! The elephant has a lazy, To be deprived of it was a mark of infamy. To comfortable-looking ear, tapering in its point, as be nailed by the ear to the pump was not a plea- if nature intended it as a whip for adventuresome sant process, and a durance vile with a vengeance. flies; and we must not overlook the dear, old Earrings are nowadays as common as earwigs, patient donkey, patient even to the burthen of the an amiable weakness with women (affected some- fat Brightonese ladies, done up in hats and times by male Yankees, and others, under the feathers, chignons and panniers. No wonder the delusion that they cure sore eyes, which they poet should exclaim :don't), but a graceful appendage, I must say, to the more graceful ear, common to all nations, and rear, unhapplily no protection against those who talk behind your back distilling malice. We can afford, however, to pass on, as did He "who wrote on the ground as though he heard them not." Would that our grievances were always thus recorded, to be effaced by the next passer by! Poor little foal of an oppressed race, We seldom see the MOTIONS. RICHARD A. PROCTOR, B.A., F.R.A.S., Author of "Saturn and its System," "Sunviews of the Earth," &c., &c. CHAPTER VI.—( Continued.) THE EARTH'S REVOLUTION. RADLEY'S discovery of the aberration of the fixed stars forms one of the most interesting narratives in the whole range of the history of astronomy. Yet, here I must perforce leave it untouched, and deal only with the phenomenon itself, since properly to relate the steps by which he was guided to that most important discovery, would occupy all the rest of the space now available to me. The great and general law, then, to which the apparent annual motions of the stars are subjected a law which must be accounted for by any theory which pretends to exhibit the real relations of the celestial bodies-is this: Every star in the heavens, whether obvious to the naked scopes, whether shining in solitary splendour or in this country to all classes. You see light and The animal begets its kind care and thanks to eye or visible only by the aid of powerful teleheavy weights, false and real gems, adorning the ear, but the beauty is in the soft, cushiony lobe, beast of burthen bludgeoned as in days gone by, lost, so to speak, in the profundities of some rich that feels elastic to the fingers-a privilege the society for its protection. or assailed with the savagery of a Balaam. ably so the former. the Dolphin, or to the music-loving propensities Rude Heiskar's seals, through surges dark, Will long pursue the minstrel's bark. "In Germany they take the shad by means of nets, to which bows of wood, hung with a number of little bells, are attached in such a manner as to chime in harmony when the bells are moved. The shad, when once attracted within the sound, will not attempt to escape while the bells continue to ring. Aelian says the shad are allured by castanets, and so delicate is the ear of the fish reported to be, that the sound of thunder terrifies them to death, and numbers are annually found thus killed on the Rhine and the Moselle." But to cite The car stands out a little from the head to other cases of acute hearing in birds, &c. :-"An catch the sounds, and the hollow cup, or concha officer confined in the Bastile of Paris begged the (shell), acts as an ear-trumpet; the outer rims governor to permit him the use of his lute to are called respectively the helix (A) or fold, and soften his confinement by the harmonies of his the antihelix, peaked portion in front, is denomi-instrument. At the end of a few days this nated the tragos (rpayoç), the hairs on which are modern Orpheus, playing on his lute, was greatly supposed to resemble a goat's beard. These, with astonished to see frisking out of their holes great the antitragos, opposite the tragos, complete numbers of mice, and descending from their star-cluster, travels once a year in a minute minor axis depends on the position of the star ellipse, whose major axis is somewhat more than two-thirds of an arc-minute in length, while its with reference to that great circle on the heavens in which the sun seems annually to travel. A star close by the pole of this circle-the ecliptic has an almost circular aberration-ellipse; one near the ecliptic itself has an aberration-ellipse so eccentric as to be almost a straight line. But every star has an aberration-ellipse of the same major axis. And that major axis, though, as I have said, minute, belongs to the order of magnitudes which are obvious to the telescopist-palpable, unmistakable, clear as the sun at noon to the worker in a well-appointed obse: vatory.* Now let us inquire what the particular law is according to which these remarkable ellipses are described by the stars, for much depends on this point. If merely a vague notion is given of the character of this instructive phenomenon, then some vague and general explanations will immediately suggest themselves to the supporters of paradox. When the exact nature of aberration is described, the proof of the earth's revolution The mere fact that Bradley, when telescopic appliances were so imperfect, at once recognised the aberrations of the first fixed star he watched with care, though he had no reason to look for or expect such a motion, is enough to show how very palpable the pheBut it may be well to add that astrononomenon is. mers can now recognise and feel certain about stellar displacements which are only about one-hundredth of the aberration motion. FIG.I will be found (by all who have sufficient intelli- | have made use of the accepted theory to describe membered that this was the problem as presented gence to understand the matter, or honesty the observed motions, this by no means involves in Bradley's time by mere observation, and the assumption that the accepted theory is correct. It is the fact, and a striking fact it is, that we cannot even describe stellar aberration conveniently without a reference to the accepted theory, so that even though that theory were false, it would still be convenient to speak of the aberrations of the stars, as being such as would correspond to such and such assumptions respecting terrestrial motion. 2 SUN enough not to pretend blindness), absolutely irrefragible. But here we have a phenomenon to explain. We have every star on the heavens announcing some great fact to us, or rather writing down year by year on the celestial concave a lesson for our instruction. To reject the lesson as meaningless, would be to abandon one of the highest and noblest faculties given to man, his desire to search out and investigate the problems set by nature for his interpretation. What, then, is the meaning of this million-on-million-fold repeated lesson? Can astronomers explain the matter? Perhaps astronomers have some far-fetched explanation, which they would force on the world by crafty argument. The best way of describing the nature of aberration is by a reference to the accepted theory of the earth's motion. Let 1,2,3,4, Fig.1, represent the earth's path (perspectively presented) around the sun, and suppose a star so placed on the heavens The case is otherwise. Astronomy can not as to occupy the pole of the ecliptic; then the only interpret the aberration motions of all the star being at a distance practically infinite, we millions of stars revealed by the telescope, but should expect the lines of sight from all the the accepted theory of astronomy would have to points in 1, 2, 3, 4, to the star, to be directed to-be abandoned if those motions did not take place. wards this point-the ecliptic pole. In other Stellar aberration was discovered as by an acciwords, the lines 1S, 28, 38, 4S, would all be at dent, was long looked on as a great source of right angles to the plane 1, 2, 3, 4. Instead of doubt and perplexity, was honest y submitted by this, when the earth is at 1, the star is seen to- astronomers to the inquiry of the world-and wards Si, the plane S1 1 passing through the then suddenly it was seen that the aberration tangent line to 1, 2, 3, 4, at 1. So when the earth motions could not but take place, if the earth is at 2, the star is seen towards s2, the plane moves as the accepted theory asserts. Let us S2 passing through the tangent to the circle inquire how this is. 1, 2, 3, 4, at 2. And similarly when the earth is at 3 or 4, the star is apparently displaced as shown, the displacement being always an angle of one-third of a minute (approximately), and always in the direction of the earth's motion. Next suppose the star placed on the ecliptic. Then the earth's path being again represented by 1, 2, 3, 4, and the lines 1S, 28, 3S, 4S, being drawn in that plane parallel to each other to indicate the direction in which one would expect to see ske star, it is found that, whereas when the earth is at 1 and 3, where she is moving in a line towards or from the star, there is no displacement; when she is at 2 and 4, where she is moving at right angles to the line of sight to the star, there is the same displacement as in the former case. Also, in this second case, the star seems more and more displaced as the earth travels from 1 to 2, then less and less till the earth is at 3, when there is no displacement; then more and more, but on the contrary side, till the earth is at 4, and so finally less and less till the earth is again at 1. It will be easily seen that in the first case the star appears to describe a circle 1, 2, 3, 4, Fig. 3, about its mean position S, while in the latter it describes a straight line 1, 2, 3, 4, Fig. 4, through its mean position S; 2, 4 in Fig. 4 being equal to the diameter of the circle 1, 2, 3, 4, in Fig. 3. RIG.S FIGS FIGS FIG. 7 FIC. 8 EIE 2 where represents the number 3.14159... or the ratio of a circle's circumference to its diameter. Hence the velocity of light is to that of the earth 365 x 24 x 60 as 2π Now : 8; or as 32850: π. the proportion of E2, S to E1 E2 where E, S Ez is an angle of about oue-third of a minute of are is or 32400. It is seen then, 1: 360 X 60 X 3 at once, that we have a satisfactory explanation even with these rough assumptions, since the 1 72 It had been independently discovered, by observations made on the eclipses of Jupiter's satellites, that light travels with finite, though inconceivable velocity. Always when Jupiter and his family were farthest from the earth, the satellites seemed tardiest to announce by appearance or by disappearance, their motion through the shadow of their primary. And so it was seen that the light messages sweeping to us from these bodies come at a definite speed to the earth. A consequence of this peculiarity had been wholly overlooked by astronomers. The light travelling in appreciably parallel lines from a difference between 32400 and 32850 is but-nd star towards the solar system, may be compared to a shower falling in parallel lines on moving part of 32400. Bnt if I had taken the mean of bodies. Now we know that in moving through a the estimates of the velocity of light from observertical shower of rain, the rain seems to fall vations made on Jupiter's eclipses, as determined somewhat towards the face. The reason is obvi- before Bradley's observation, and Bradley's estious; thus, suppose a traveller's face at 1, Fig. 6, mate of the aberration of the star y Draconis when a a rain drop is at R, and that by the time as made before he knew what theory required, he reaches 2, the rain drop is at R2, it is clear the coincidence would have been found very much that the drop will seem to have fallen from a position in front of him, and in the direction indicated by the dotted lin- s; and if we conceive of the motion of a small body travelling in a circle under a vertical shower, we shall see at once that this property may be made to illustrate every case of stellar aberration, by assuming different positions, as 1, 2, 3, in Fig. 7, for the circle in which the body moves under the shower. It will be seen, though, that in order that this explanation may hold, it is necessary that the rate of motion of the earth should bear an appreciable relation to the enormous velocity of light. If rain fell a thousand times as fast as it actually does, the fastest runner would not find that a vertical rain-shower would seem to fall appreciably towards his face. Now, apart from all considerations of the real size of the earth's orbit, or of the rates of motion either of light or of the earth in her orbit, we can at once test this explanation of aberration. It had been independently shown by Römer that light takes about eight When the star is somewhere between either minutes in crossing the radius of the earth's pole of the ecliptic and the ecliptic itself, it de- orbit; the earth occupies a year in travelling scribes an ellipse, as 1, 2, 3, 4, Fig. 5, always reach- round the circumference of the circle; all we ing its greatest excursion as at 2 and 4, when want to know is, whether the displacement of a the earth is travelling in a direction at right star over an are of about one-third of a minute, angles to the line of sight to the star (which corresponds to these re ations. What we require necessarily happens twice a year), and its least is, that supposing S. E to be the distance traexcursion at land 3, when the earth is travelling versed by light in any time, El E2 the distance as nearly as it can towards or from the star traversed by the earth in the same time, S1 E2 171 (which also necessarily happens twice a year). being a right angle, the angle E1 S E2 should be Now it is to be noticed here that though I about one-third of a minute of arc. Let it be re closer. Here, then, we have a perfect proof of the earth's revolution. No question can remain that the lesson really taught us by the stars as they annually traverse their aberration ellipses is this, that the earth annually traverses a nearly circular path round the sun. This interpretation accounts for all the peculiarities of the stellar aberration motions; nay, the theory of the earth's motion requires every one of those peculiarities. No other theory has ever been put forward in explanation of stellar aberration, and it may be alleged, with more than confidence, with the fullest certainty of conviction, that no other theor can explain the phenomenon. CHAPTER VII. THE EARTH'S MOTION AS AN ATTENDANT ON THE SUN IN HIS JOURNEY THROUGH SPACE. Since the stars are observed to be slowly shifting their positions on the celestial vault, and therefore presumably in space, it is obviously suggested that the sun, which is but a member of the sidereal family, has also his proper motion through space. It is a difficult problem to determine what that motion is, because all we have to * I need take no further notice of a so-called expla nation in a work purporting to be written by a Cambridge wrangler (name not given), than to remark that it does not even pretend to explain details, and that what it does pretend to do suffices to exhibit the utter ignorance of the writer as to the real nature of the problem. I do not say that the writer is not a Cambridge wrangler, because I know from my own expe rience that a man may become a wrangler without knowing even the definitions of astronomy. Buve had say that the writer, being a wrangler, should have d sense enough to know that before pretending to write on astronomy, he ought to have acquired a better knowledge of the subject than he shows himself to have. |