The nature of capillary attraction was then examined, and the mode of supplying plants with moisture by a series of minute capillary tubes explained. The process of making mill-stones, operating as it does by the power of capillary attraction, furnishes also a striking instance of the power of moisture, when thus employed in overcoming resistances: the method may be easily understood: when a block of stone has been found sufficiently large, it is cut into the form of a cylinder, several feet in height; and the question is then how to cut it into horizontal pieces, to make as many millstones. For this purpose, circular and horizontal indentations are cut out quite round it, and at proper distances, according to the thickness to be given to the mill-stones; wedges of willow dried in an oven are then driven into the indentations, by means of a mallet; when the wedges have sunk to a proper depth, they are moistened, or exposed to the air during the humidity of the night, and next morning the different pieces are found separated from each other. The splitting of the stone is owing to the effect of attraction, by which the water is made to rise in the exceedingly narrow capillary tubes with which the wood is filled. The lower the centre of gravity is, in any body, the more stable must that body of necessity be found; and on this account it is, that so much danger arises from the overloading of coaches and caravans. In the improved stage-coach, however, this defect is in a great measure remedied, by placing the outside passengers in the lowest part of the vehicle. Whilst the caravan proprietor, on the contrary, as if in defiance of reason and common sense, piles goods on the top of his ponderous vehicle, till the slightest oscillation threatens destruction to all within its reach. In the equilibrium of animals many circumstances occur illustrative of the centre of gravity. When a person stands on one foot and leans forward, the other foot is immediately elevated, which, operating like a long lever, tends to bring back the centre of gravity within the foot on which he is supported. When standing forward on the point of the toe, a still narrower base is then offered for support, and some difficulty is found in ensuring a continued equilibrium. The regularly increasing velocity with which a body is drawn towards the earth's centre, may be adduced as an additional illustration of the force of gravity: a stone, for instance, beginning to fall, by no means retains the same velocity through its whole descent, but acquires more and more motion every instant; for we well Having examined the amount of increase that invariably occurs in the velo city of a ponderous body falling through the air, it may be proper to state, that the speed with which a body actually falls is much greater than we have hitherto found advisable to view it. In the preceding calculation, we have, for the sake of simplicity, considered the body as falling but one foot, in the first second, and three feet in the second second. Now, a heavy body will actually fall through a space equal to more than sixteen feet in the first second, and four times that, or sixty four feet, in the second second. In the third second, it will have fallen through one hundred and forty-four feet; and in the next, or fourth second, through two hundred and fifty-six feet. So that, to get the actual velocity, it will only be necessary to square the time of falling, and then multiply the product by sixteen, which will give the absolute distance in feet. Traces of the principle of gravitation are to be found in writers of great antiquity. But their speculations on this subject do not go beyond a vague notion of a tendency, which the planets have to one another, as to a common centre. It would contribute little, either to the entertainment or instruction of my auditors, to collect all the passages of ancient authors that speak of this principle. The revival of the true system of the world, by Copernicus, introduced the most admirable (LITERARY AND SCIENTIFIC INSTITUTIONS simplicity in the explanation of the planetary motions, and likewise led to more just conjectures concerning the laws by which they are upheld. Copernicus himself attributed the round figure of the planets to a tendency which their parts possess of uniting with one another; thus extending to all the planets that which we observe at the surface of the earth. He stopped short, indeed, at this point, conceiving attraction to be confined to the matter of each planet, without making it extend from one planet to another, so as to unite all the bodies of the system. This step was made by the bold and systematic genius of Kepler. Adopting the opinion of Dr. Gilbert of Colchester, that the earth is a great magnet, Kepler formed to himself a notion of attraction, in some respects remarkably just. He says that the earth and moon attract one another; and, were it not for some powers which retain them in their orbits, they would move towards one another, and would meet in their common centre of gravity. He attributes the tides to the moon's attraction, which heaps up the waters of the ocean immediately under her. But, in many respects, his notions of attraction were fanciful and extravagant; a more perfect knowledge of the laws of motion than had been attained to, in his time, and a new geometry, were both wanting, in order to guide him in his research without danger of wandering. Yet he was able to penetrate so far into the causes of the planetary motions, as to foresee that they would not long continue latent; he tells us, he was persuaded "that the full discoveries of those mysteries was reserved for the next age, when God would reveal them." So full an exposition of the physical system of the world, as is contained in the writings of Kepler, could not fail to draw the attention of succeeding philosophers. Many remarks concerning the principle of gravitation are to be found in the writings of Fermat, Roberval, Borelli, and other authors. But no one, before Newton, entertained so clear and systematic a view of the doctrine of universal gravitation as Dr. Robert Hook. In his work on the motion of the earth, published in 1674, twelve years before the appearance of Newton's Principia, he lays down these three positions as the foundations of his system, viz. "1st. That all the heavenly bodies have not only a gravitation of their parts to their own proper centre, but likewise that they mutually attract each other within their spheres of action. 2dly. That all bodies having a simple motion, will continue to move in a straight 299 line, unless "continually deflected from it by some extraneous force, causing them to describe a circle, or an ellipse, or some other curve. "3dly. This attraction is so much the greater, as the bodies are nearer." The principle of universal gravitation is here very precisely enunciated. Dr. Hook seems to have clearly perceived that the planetary motions are the result of an attraction towards the sun, and of a rectilineal motion produced by a projectile force. Not having discovered the law according to which the force diminishes, as the distance of the sun increases, he contrived experiments to elucidate his theory. Having placed another ball upon a table, immediately under the point of suspension, he caused the suspended ball to revolve round the stationary one. When the movable ball was pushed laterally with the force properly adjusted to its deviation from the perpendicular, it described an exact circle round the ball on the table; in other cases, it described an ellipse, or an oval resembling an ellipse, having the other ball in the centre. Dr. Hook observed, that although this experiment, in some measure, illustrated the planetary motions, yet it did not represent them accurately; because the ellipses, which the planets describe, have the sun placed in one focus, and not in the centre. Thus, at the appearance of Newton, many things were known, or rather surmised, that prepared the way for the discovery of the principle which regulates the celestial motions. This does not detract, in any degree, from the glory of Newton, who, discarding the conjectures of his predecessors, proposed to himself to investigate, with mathematical strictness, the law of the attractive force. He invented a new kind of geometry, which was necessary to enable him to accomplish his purpose. With this help, and by admitting nothing without the sanction of the established principles of dinamics, he deduced from the motions of the celestial bodies the law of universal gravitation, the most important and the most general truth hitherto discovered by the industry and sagacity of man; viz. "That all the particles of matter attract one another, directly as their masses, and inversely as the squares of their distances." Having thus experimentally examined the nature of gravitation as far, at least, as that can be effected with reference to the present early stage of my course, it may now be advisable to suppose a question which is very likely to arise in the minds of a large portion of my auditory. It is this :-"What is gravitation?" or how can one body act on another without some medium for communicating its influence? That such a power does exist, we have sufficient proofs during every moment of our existence; though unfortunately, from its permanence, we lose the thankfulness which should arise for its protecting influence. Gravitation does exist, and dreadful would be the consequences, though but for an instant, of its non-existence. Our globe, hurried from its ordinary path, where she rolls self-balanced upon her own centre, would be involved in a ruin more destructive, and a chaos more inextricable, than that of the universal deluge itself. At the close of Mr. Partington's lecture, the President briefly addressed the members, congratulating them on the improved prospects of the Institution, and stated that the committee had abstained from any very extensive purchase of books, under the impression that many authors and publishers would be disposed to furnish their works gratuitously. Mr. Gibson concluded by stating that, as the arrangements were nearly completed, a catalogue of the books would be prepared for the members, who would thus immediately derive every advantage that the library could afford. LONDON INSTITUTION. THE attempt of Mr. Abernethy, on a late occasion, to put down lecture reporting by the strong arm of the law, is singularly contrasted by the liberal feeling expressed by sir James Edward Smith, in a lecture delivered at the London Institution, on Monday last. The worthy president of the Linnean Society stated, in his preliminary observations, that he knew that some professors objected to the publication of their lectures; and he added, that it had frequently fallen to his lot to read books and listen to lectures of which his own discourses had formed the principal materials; but this, so far from exciting his anger, had furnished the highest gratification, and he should at all times be glad to see his humble efforts for the diffusion of useful knowledge beneficially employed. The following is a brief analysis of sir James's two first lectures: Monday, May 2.-A general view of the objects of systematic Botany, and its recommendations. How the science originated in that of medicine, and how it has assumed a philosophical shape. Different objects of its cultivators, and their different success. Of natural and artificial classification. Genera. Species, and varieties. Thursday, May 5.- Of the general structure of plants. Theory of vegetation; how it has been established. Ideas of some vegetable physiologists who have left it imperfect. Theory of Du Hamel. Conveyance of the sap. Effects of air, light, and heat upon the sap, in the different organs of plants. On Monday next, the physiology of flowers and fruits will be examined, with various examples of their structure. Dr. Birkbeck's third lecture to the members of the London Mechanics' Institution will appear in our next Number. SCIENCE, AND USEFUL DISCOVERIES IN THE ARTS. RED SNOW OF THE ALPS. A NOTICE, of which the following is a part, was read to the Society of Natural History, of Geneva, by M. Peschier: "I received from M. Barras, canon of the convent of St. Bernard, a small bottle of water collected from the melting of this snow. The note accompanying it stated, that the spots of red snow assumed a deeper tint as the season advanced; that the portion from whence the water was procured had a coffee colour on its sur face, but on examining it about two inches in depth, it had a red colour. A deposit of the colour of moist earth occupied the bottom of the bottle, but on inclining it, the deposit reflected a red tint, like that of the snow; and having, in company with MM. de Candolle and Prevost, examined it microscopically, we found that the red tint was due to the presence of small spherical globules of a bright red colour, which were surrounded by a gelatinous membrane, transparent,and slightly yellow,-the size of which varied from three to six millimetres in apparent diameter in certain cases they were arranged in lines, representing fibres; and they were mixed with fragments of moss and dust detached from the rocks. A comparative observation was made on the deposit from the water of the red snow of the North, brought by captain Ross, of. which M. de Candolle possessed a small quantity; and it was found that the globules in it were identical with those of the Alpine snow; so that these spots must be due to the developement of this kind of plant. M. de Candolle, who has studied them closely, does not consider : WATER-COLOUR EXHIBITION. 301 them as belonging to the Uredo, but form- of the ductility and the grandeur of this ing a new genus. MONT BLANC AND MONT ROSA. Mont Blanc WATER-COLOUR EXHIBITION. THE twenty-first season of this elegant and delightful source of mental entertainment commenced on Monday, the 25th ult.; and the novelty that drew its first visitors has been succeeded by the still stronger attraction of its sterling merits. master's conception, and of the power of his pencil to mingle and harmonize the diversified objects of a variegated and M. de Welden, after a very elaborate busy scene. The still, charming aspect examination of the various measurements of FIELDING's Inverary (in Argyleshire) of Mont Blanc and Mont Rosa, gives the afforded us great pleasure. The time of following as the results, which appear to the day he has selected for this beautiful be most accurate:view is the morning, and the "sweet hour feet. of prime " is rendered obvious by the 15,737 universality of his aurora-like tints. The 15,157 receding shore is remarkably fine, the sky is tenderly coloured, the distance is preserved with great ability, and the whole forms as faithful a representation of Inverary as the mind can conceive. RICHTER'S School in Repose, is founded on an idea highly favourable to the exercise of the artist's fancy; and its adoption, we believe, is new. A schoolmistress, with all her young frolicksome pupils about her, is seated in her elbow-chair fast asleep. The artist, solicitous to take every advantage of his subject, exhibits the wanton urchins in the full practice of all their juvenile pranks; one is tying on the fool's-cap; another has got her governess's snuff box, and is setting her companions a sneezing; a third is mimicking her dancing-master; and a fourth is seen under the table, sewing the old lady's petticoat to the carpet. The whole is full of character; and the countenances and colouring, vieing with the excellence of the general design, complete the intended effect, and demonstrate MR. RICHTER'S talent for this species of graphic humour. Neath Abbey reflects much credit on DEWINT's taste in the tranquil style of landscape. The sheet of water over which the eye passes to the abbey, in the mid-distance, is beautifully tinted, and the surrounding scenery is finely combined in its colouring. The modesty of nature is observed throughout; and the aggregate effect is sweetly calm and reposing. Cox's Eneas and Achates is ably designed, and the objects are judiciously disposed; but the colouring is too gaudy; by aiming at too much effect the artist has attained less of it than he might have produced. The composition is good; but the execution is too assuming to satisfy the eye that looks for, and is contented with, things as they are presented to us by nature's mirror. The familiar scene of Belgrave House, (Millbank,) by VARLEY, is, in our opinion, one of his most pleasing performances. The bank, the mansion, the Thames on the right, and Westminster-bridge in the front distance, form an attractive assemblage of objects, and are brought together with the advantage of that harmony of colouring for which this artist is so remarkable. HILL's Scene on the River Mole would The pieces sent in are very numerous, and not a few of them claim our warmest commendation. They are partly from the pencils of members of the society, partly the labours of honorary associates, and amount to nearly three hundred and fifty. Of so great a number of pictures, some, of course, are of inferior excellence; but, in justice to the larger portion, we must say that they display much fertility of imagination, as well as cultiva ed judgment, and are brilliant specimens of English talent for this province of painting. To remark upon, or even to name, every piece that caught our eye and rivetted our attention, would demand more space than the variety which characterises our pub lication will allow; but the principal of these too imperiously demand the critic's notice to pass without our comment. With the Distant view of Ulleswater, Cumberland, by DEWINT, we were greatly pleased. The distant hills are richly, though faintly, tinted. The shady recess, leading to their acclivities, is judiciously managed; and the foreground is bold without glare, and relieves, without weakening, the less prominent parts of the picture. STEPHANOFF'S Reconciliation of Selim and Nourmahall, is distinguished from every other piece of the kind in the exhibition, by the happy grouping of the various figures, the fine sensibility depicted in the face of Nourmahall, the tender return of attachment that kindles in the eye, and mantles in the cheek of Selim, and the rich glow, and superb style of execution, that pervade the whole tableau. The Ponte di Rialto, by PROUT, is a magnificent performance. The figures, the buildings, the boats, and the water, are combined proofs deserve particular notice, were it only on account of its woody beauties; but the cattle are so full of nature, both in their drawing and finishing, as to greatly enhance the value of the picture. Many similar samples of excellence are scattered round the room; but we hasten to notice some of the pieces of MR.Barpet, who exhibits this season no fewer than thirty evidences of his genius and industry. So truly excellent are the greater portion of these, that we wish our limits would allow us to point out their particular merits. With his Evening, founded on a description by Thomson; his Morning, (No. 45;) his River Scene, (No. 51;) his Rookery; his Mid-Day; his Durham Cathedral, his Ancient City, and his Debarkation, we were most forcibly struck. All his productions bespeak the ample conception, the taste for disposition, and the facile execution of a real and great master; an obvious consistency prevails throughout his pictures, and a style peculiarly his own always marks his handling. Without wishing to derogate from the merits of his numerous compeers in his own line of art, we must say that this artist is unrivalled in the provinces of design, drawing, and colouring; no other master is so comprehensive in his ideas, so luxurious in his tints; no other so happy in disposing of his objects, and in producing, out of a multiplicity of parts, an analogous whole, an unity of effect, a combined impression, which at once seizes on the attention, and charms the beholder. But amid all these merits, MR. BARRET is subject to one fault common among inferior artists. He sometimes puts the nominal subject of his picture in a corner, and renders every thing conspicuous but that which furnishes the title to the piece. His Weary Traveller comes under this censure. The landscape is every thing, the sleeping man nothing; for while a thousand beautiful objects court the eye's attention, he is sunk in a shady nook, and almost escapes observation. On the whole, though in this year's exhibition we find some indifferent pictures, and in the catalogue of names miss several of our old favourites, particularly HEAPHY and GLOVER, we feel its strong title to our eulogy. The defective pieces are greatly outnumbered by the productions of sterling merit; and the reputation of our water-colour artists will not fail to be raised by the present assemblage of their ingenious labours. To the Editor of the Circulator. THE following lines were written by 3 "All things are made of shells." FROM atoms in confusion hurl'd, Old Epicurus built a world; Maintain'd that all was accidental, Whether corporeal pains or mental, That neither head, arms, heart, nor mind By any foresight were design'd; That feet were not devis'd for walking; For eating, teeth; nor tongues for talking That chance the casual texture made, And then each member found his trade And in this vortex of stark nonsense, He buried virtue, truth, and conscience For this he spent much studious toil, And oft consum'd the midnight oil; Each year produc'd long labour'd volumes Which cover'd half the attic columns. And thus his sect spread far around, In Asia, Rome, and Greece renown'd. For all the bad receiv'd with glee, This hodge-podge of iniquity. D at length resolves to list Under this grand cosmogonist. He too renounces his Creator, And forms all sense of senseless matter. ROYAL ACADEMY. ON Monday last the annual exhibition was opened to the public. The display this year is perfectly distinct in its cha racter from most preceding ones, from the number of historical pictures. The magnitude of these has excluded a great number of portraits and small pictures; so that the whole has an air rather of a French than a British collection of works of art. The late MR. FUSELI'S composition of Comus, is the first for vigorous invention, and for the highest science in art. The interesting moment chosen,is that when the brothers are in the act of rushing upon the enchanter, dashing the cup from his hand, and delivering their sister from his spell. |