Читать книгу: «The Mirror of Literature, Amusement, and Instruction. Volume 14, No. 405, December 19, 1829», страница 7

SPIRIT OF DISCOVERY

POPULAR PHILOSOPHY

Dr. Arnott's Elements of Physics

Vol. ii. Part I

We are warm friends to the diffusion of knowledge, and accordingly receive the present portion of Dr. Arnott's work with much satisfaction. We believe the sale of the first volume to have been almost unprecedentedly rapid, (a fourth edition being called for within two years) in comparison with the usual slow sale of scientific works. This success may easily be traced. The title of the work is not extraordinarily inviting, illustration, not embellishment, is attempted in a few outline diagrams, and the only external inducement to read, is a plain, legible type, to suit all sights. Looking further, we find the great cause in the manner as well as the matter of the volume, which is throughout a text-book of plain-spoken philosophy, or as the author says in his title-page, "independently of technical mathematics." Again, in his introductory chapter on "Imponderable Substances," he says, "To understand the subjects as far as men yet usefully understand them, and sufficiently for a vast number of most useful purposes, it is only necessary to classify important phenomena, so that their nature and resemblances may be clearly perceived." The main error of most people who write on philosophical subjects, or the stumbling-block of all students, has been that of the writer presuming too much upon the cultivated understanding of his reader. Thus, in the midst of very familiar explanations we have often seen technicalities which must operate as a wet blanket on the enthusiasm of the reader; and break up the charm which the subject had hitherto created. Upon this principle, treatise upon treatise has been published without effecting the primary object. The matter of Dr. Arnott's work, however, appears to us to be in strict accordance with its title—elementary; but it is accompanied with a variety of explanations of familiar facts on philosophical principles, which possess attractions of a most amusive character.

The present portion of Dr. Arnott's work comprehends the subjects of Light and Heat, which admit of more familiar illustration than any other branches of Natural Philosophy. Of this advantage the author has fully availed himself in a variety of familiar exemplars, which, to speak seriously are brought home to our very firesides. A few of these facts will form a recreative page or two for another MIRROR: in the meantime we quote a few illustrative observations on the most interesting exhibitions of the day:—

"Common paintings and prints may be considered as parts of a panoramic representation, showing as much of that general field of view which always surrounds a spectator, as can be seen by the eye turned in one direction, and looking through a window or other opening. The pleasure from contemplating these is much increased by using a lens. There is such a lens fitted up in the shops, with the title of optical pillar machine, or diagonal mirror, and the print to be viewed is laid upon a table beyond the stand of the lens, and its reflection in a mirror supported diagonally over it, is viewed through the lens. The illusion is rendered more complete in such a case by having a box to receive the painting on its bottom, and where the lens and mirror, fixed in a smaller box above, are made to slide up and down in their place to allow of readily adjusting the focal distance. This box used in a reverse way becomes a perfect camera obscura. The common show-stalls seen in the streets are boxes made somewhat on this principle, but without the mirror; and although the drawings or prints in them are generally very coarse, they are not uninteresting. To children whose eyes are not yet very critical, some of these show boxes afford an exceeding great treat."

Cosmoramas and Dioramas.

"A still more perfect contrivance of the same kind has been exhibited for some time in London and Paris under the title of Cosmorama (from Greek words signifying views of the world, because of the great variety of views.) Pictures of moderate size are placed beyond what have the appearance of common windows, but of which the panes are really large convex lenses fitted to correct the errors of appearance which the nearness of the pictures would else produce. Then by farther using various subordinate contrivances, calculated to aid and heighten the effects, even shrewd judges have been led to suppose the small pictures behind the glasses to be very large pictures, while all others have let their eyes dwell upon them with admiration, as magical realizations of the natural scenes and objects. Because this contrivance is cheap and simple, many persons affect to despise it; but they do not thereby show their wisdom; for to have made so perfect a representation of objects, is one of the most sublime triumphs of art, whether we regard the pictures drawn in such true perspective and colouring, or the lenses which assist the eye in examining them.

"It has already been stated, that the effect of such glasses in looking at near pictures, is obtainable in a considerable degree without a glass, by making the pictures very large and placing them at a corresponding distance. The rule of proportion in such a case is, that a picture of one foot square at one foot distance from the eye, appears as large as a picture of sixty feet square at sixty feet distance. The exhibition called the Diorama is merely a large painting prepared in accordance with the principle now explained. In principle it has no advantage over the cosmorama or the show box, to compensate for the great expense incurred, but that many persons may stand before it at a time, all very near the true point of sight, and deriving the pleasure of sympathy in their admiration of it, while no slight motion of the spectator can make the eye lose its point of view."

The Colosseum.

"A round building of prodigious magnitude has lately been erected in the Regent's Park, in London, on the walls of which is painted a representation of London and the country around, as seen from the cross on the top of St. Paul's Cathedral. The scene taken altogether is unquestionably one of the most extraordinary which the whole world affords, and this representation combines the advantages of the circular view of the panorama, the size and distance of the great diorama, and of the details being so minutely painted, that distant objects may be examined by a telescope or opera-glass.

"From what has now been said, it may be understood, that for the purpose of representing still-nature, or mere momentary states of objects in motion, a picture truly drawn, truly coloured, and which is either very large to correct the divergence of light and convergence of visual axes, or if small, as viewed through a glass, would affect the retina exactly as the realities. But the desideratum still remained of being able to paint motion. Now this too has been recently accomplished, and in many cases with singular felicity, by making the picture transparent, and throwing lights and shadows upon it from behind. In the exhibitions of the diorama and cosmorama there have been represented with admirable truth and beauty such phenomena as—the sun-beams occasionally interrupted by passing clouds, and occasionally darting through the windows of a cathedral and illuminating the objects in its venerable interior—the rising and disappearing of mist over a beautiful landscape, runningwater, as for instance the cascades among the sublime precipices of Mount St. Gothard in Switzerland;—and most surprising of all, a fire or conflagration. In the cosmorama of Regent-street, the great fire of Edinburgh was admirably represented:—first that fine city was seen sleeping in darkness while the fire began, then the conflagration grew and lighted up the sky, and soon at short intervals, as the wind increased, or as roofs fell in, there were bursts of flame towering to heaven, and vividly reflected from every wall or spire which caught the direct light—then the clouds of smoke were seen rising in rapid succession and sailing northward upon the wind, until they disappeared in the womb of distant darkness. No one can have viewed that appalling scene with indifference, and the impression left by the representation, on those who knew the city, can scarcely have been weaker than that left on those who saw the reality. The mechanism for producing such effects is very simple; but spectators, that they may fully enjoy them, need not particularly inquire about it."

Even for the present we cannot omit mention of the delight with which we have read several of the more playful portions of the present work; we allude to such passages as the Influence of Heat on Animated Beings, in which Dr. Arnott has really blended the pencil of the artist with the pen of the philosopher, and thus produced many sketches of extreme picturesque beauty.