The observations contained in the preceding chapters prepare us for appreciating the value of the stereoscope as an indispensable auxiliary in elementary as well as in professional education. When the scholar has learned to read, to write, and to count, he has obtained only the tools of instruction. To acquire a general knowledge of the works of God and of man—of things common and uncommon—of the miracles of nature and of art, is the first step in the education of the people. Without such knowledge, the humblest of our race is unfit for any place in the social scale. He may have learned to read his Bible, and he may have read it after he had learned to read;—he may have committed to memory every sentence in the Decalogue;—he may have packed into the storehouse of his brain all the wisdom of Solomon, and all the divine precepts of a greater than Solomon, while he is utterly ignorant of everything above him, around him, and within him,—ignorant, too, of the form, the magnitude, and the motions of his terrestrial home,—ignorant of the gigantic structures which constitute the material universe,—ignorant of the fabrics which industry prepares for his use, and of the luxuries which commerce brings from the ends of the earth and places at his door,—ignorant even of the wonderful operations of that beneficent commissariat, which is every moment, while he sleeps and dreams, elaborating the materials by which he is fed and clothed.

Were we to say, though we do not say it, that in our own country the teachers, so penuriously endowed by the State, are not much in advance of their pupils, we should err only in stating what is not universally true; and yet there are men of influence and character insisting upon the imposition of sectarian tests, and thus barricading our schools against the admission of the wisest and the fittest masters! And while every civilized community in the world is eagerly teaching their people, irrespective of religious creeds, the same bigots, civil and ecclesiastical, in our own country, have combined to resist the only system of education which can stem the tide of vice and crime which is desolating the land.

Missionary labour and reformatory institutions, valuable as they are, presuppose an educated community. To instruct and reform a race that can neither read their Bible nor derive knowledge from books, is a task beyond human achievement. The dearest interests of society, therefore, call loudly for Secular Education,—the greatest boon which philanthropy ever demanded from the State. The minister who, in the face of sectarian factions, dares not identify himself with a large legislative measure for the education of the people, and resigns office when he fails to carry it, prefers power to duty, and, if he ever possessed it, divests himself of the character of a statesman and a patriot. He may be justified in punishing the law-breaker who cannot read his statutes, but he is himself the breaker of laws of a higher order, and sanctioned by a higher tribunal.

If the education of the people is to be attempted either by partial or comprehensive legislation, the existing system is utterly inefficient. The teacher, however wisely chosen and well qualified, has not at his command the means of imparting knowledge. He may pour it in by the ear, or extract it from the printed page, or exhibit it in caricature in the miserable embellishments of the school-book, but unless he teaches through the eye, the great instrument of knowledge, by means of truthful pictures, or instruments, or models, or by the direct exhibition of the products of nature and of art, which can be submitted to the scrutiny of the senses, no satisfactory instruction can be conveyed.[65] Every school, indeed, should have a museum, however limited and humble. Even from within its narrow sphere objects of natural history and antiquities might be collected, and duplicates exchanged; and we are sure that many a chimney-piece in the district would surrender a tithe of its curiosities for the public use. Were the British Museum, and other overflowing collections, to distribute among provincial museums the numerous duplicates which they possess, they would gradually pass into the schools, and before a quarter of a century elapsed, museums would be found in every proper locality.

As we cannot indulge in the hope that any such boon will be conferred on our educational institutions, it becomes an important question how far it is possible to supply the defect by the means within our reach. The photographic process may be advantageously employed in producing accurate representations of those objects, both of nature and of art, which it would be desirable to describe and explain in the instruction of youth; but as experience has not yet taught us that such pictures will be permanent, and capable of resisting the action of time and the elements, it would be hazardous to employ them in the illustration of popular works. It is fortunate, however, that the new art of galvanography enables us, by a cheap process, to give to photographs the permanence of engravings, and to employ them in the illustration of educational works.[66]

But however much we may value such an auxiliary, representations or drawings, on a plane, of solids or combinations of solids at different distances from the eye, are in many cases unintelligible even to persons well informed; so that, on this ground alone, we cannot but appreciate the advantages to be derived from binocular pictures and their stereoscopic relievo, not only in the instruction of youth, but in the diffusion of knowledge among all ranks of society.

One of the most palpable advantages to be derived from the illustration of school-books by pictures in relief, is the communication of correct knowledge of the various objects of natural history. If, as we have already shewn, the naturalist derives important assistance in his studies from correct representations of animated nature, how much more valuable must they be to the scholar who never saw, and may never see the objects themselves. In the department of zoology, the picture might frequently be taken from the living animal, standing before the camera in vigorous life and transcendent beauty; or when this cannot be done, from the fine specimens of zoological forms which adorn our metropolitan and provincial museums. The trees and plants, too, of distant zones, whether naked in their osteology, or luxurious in their foliage, would shew themselves in full relief;—the banyan, clinging with its hundred roots to the ground,—the bread-fruit tree, with its beneficent burden,—the cow tree, with its wholesome beverage,—the caoutchouc tree, yielding its valuable juice,—or the deadly upas, preparing its poison for the arrow of the savage or the poniard of the assassin.

With no less interest will the schoolboy gaze on the forms of insect life, which will almost flutter before him, and on the tenants of the air and of the ocean, defective only in the colours which adorn them. The structures of the inorganic world will equally command his admiration. The minerals which have grown in the earth beneath his feet, and the crystals which chemistry has conjured into being, will display to him their geometric forms, infinite in variety, and interesting from their rarity and value. Painted by the very light which streamed from them, he will see, in their retiring and advancing facets, the Kohinoor and other diamonds, and the huge rubies, and sapphires, and emeralds, which have adorned the chaplet of beauty, or sparkled in the diadem of kings. The gigantic productions of the earth will appeal to him with equal power,—the colossal granites, which have travelled in chariots of ice, and the rounded boulders, which have been transported in torrents of mud; and while he admires, in their strong relief, the precipices of ancient lava—the Doric colonnades of basalt—the upheaved and contorted strata beside them, and the undisturbed beds which no internal convulsions have shaken, he will stand appalled before the fossil giants of the primeval world that trod the earth during its preparation for man, and have been embalmed in stone to instruct and to humble him.

In acquiring a knowledge of physical geography, in which the grander aspects of nature arrest our attention, their stereoscopic representations will be particularly instructive. The mountain range, whether abrupt in its elevation, or retiring from our view,—whether scarred with peaks or undulating in outline,—the insulated mountain tipped with snow or glowing with fire,—the volcano ejecting its burning missiles,[67]—the iceberg fixed in the shore, or floating on the deep,—the deafening cataract,—the glacier and its moraines, sinking gently to the plains,—and even the colossal wave with its foaming crest, will be portrayed in the binocular camera, and exhibited in all the grandeur and life of nature.

The works of human hands,—the structures of civilisation, will stand before the historian and the antiquary, as well as the student, in their pristine solidity, or in their ruined grandeur,—the monuments by which sovereigns and nations have sought to perpetuate their names,—the gorgeous palaces of kings,—the garish temples of superstition,—the humbler edifices of Christian faith,—the bastions and strongholds of war, will display themselves in the stereoscope as if the observer were placed at their base, and warmed by the very sun which shone upon their walls.

Although few of our village youth may become sculptors, yet the exhibition of ancient statues in their actual relief, and real apparent magnitude, cannot fail to give them salutary instruction and rational pleasure. To gaze upon the Apollo Belvidere,—the Venus de Medici,—the Laocoon, and the other masterpieces of ancient art, standing in the very halls which they now occupy; or to see the chef d’œuvres of Canova, Thorvaldsen, and Chantrey, or the productions of living artists in their own studio, with the sculptor himself standing by their side, will excite an interest of no ordinary kind.

From the works of the architect, the engineer, and the mechanist, as exhibited in full relief, the student, whether at our schools or colleges, will derive the most valuable instruction. The gigantic aqueducts of ancient and modern times,—the viaducts and bridges which span our valleys and our rivers, and the machinery in our arsenals, factories, and workshops, will be objects of deep interest to the general as well as the professional inquirer.

There is yet another application of the stereoscope to educational purposes, not less important than those which have been mentioned. In the production of diagram representing instruments and apparatus, which cannot be understood from drawings of them on a plane, it will be of incalculable use to the teacher to have stereoscopic pictures of them. In every branch of physical science, diagrams of this kind are required. When they are intended to represent apparatus and instruments, either for illustrating known truths, or carrying on physical researches, binocular pictures can be easily obtained; but when the diagrams have not been taken from apparatus, but are merely combinations of lines, we can obtain binocular photographs of them only from models constructed on purpose. These models will give binocular representations in various azimuths, so that the true position of planes at different inclinations, and lines at various angles with each other, and at different distances from the eye, will be readily apprehended. Astronomical diagrams, in which orbits, &c., may be represented by wires, and optical figures, in which the rays may be formed by threads or wires, would be thus easily executed.

Among the binocular diagrams, consisting of white lines upon a black ground, which have been executed in Paris, there is one representing the apparatus in which a ray of light, polarized by reflexion from a glass plate, passes through a crystallized film perpendicular to the plane of the paper, and is subsequently analysed by reflexion from another plate at right angle to the following plate. This diagram, when placed in relief by the stereoscope, gives as correct an idea of the process as the apparatus itself.

As an auxiliary in the investigation of questions of difficulty and importance, both in physics and metaphysics, the stereoscope is peculiarly valuable. It enables us to place in its true light the celebrated theory of vision on which Bishop Berkeley reared the ideal philosophy, of which he was the founder, and it gives us powerful aid in explaining many physical phenomena which have long baffled the ingenuity of philosophers. It would be out of place to give any account of these in a work like this, but there is one so remarkable, and at the same time so instructive, as to merit special notice. In order to exhibit, by means of three diagrams, a solid in relief and hollow at the same time, which had not been previously done, I executed three drawings of the frustum of a cone, resembling those in Fig. 31, so that the left-hand one and the middle one gave the hollow cone, while the middle one and the right-hand one gave the raised cone. Having their summits truncated, as in the figure, the cones exhibit, in the one case, a circle at the bottom of the hollow cone, and in the other, a circle on the summit of the raised cone. When these three diagrams[68] are placed in an open lenticular stereoscope, or are united by the convergency of the optical axes, so that we can not only see the hollow and the raised cones, but the flat drawing on each side of them, we are enabled to give an ocular and experimental proof of the cause of the large size of the horizontal moon, of her small size when in the meridian or at a great altitude, and of her intermediate apparent magnitude at intermediate altitudes,—phenomena which had long perplexed astronomers, and which Dr. Berkeley, rejecting previous and well-founded explanations, ascribed to the different degrees of brightness of the moon in these different positions.

As the circular summit of the raised cone appears to be nearest the eye of the observer, the summit of the hollow cone farthest off, and the similar central circle in the flat drawing on each side, at an intermediate distance, the apparent distances from the eye of different and equal circles will represent the apparent distance of the moon in the zenith, or very high in the elliptical celestial vault,—the same distance when she is in the horizon, and the same when at an intermediate altitude. Being in reality of exactly the same size, and at the same distance from the eye, these circular summits, or sections of the cone, are precisely in the same circumstances as the moon in the three positions already mentioned. If we now contemplate them in the lenticular stereoscope, we shall see the circular summit of the hollow cone the largest, like the horizontal moon, because it seems to be at the greatest distance from the eye,—the circular summit of the raised cone the smallest, because it appears at the least distance, like the zenith or culminating moon,—and the circular summits of the flat cones on each side, of an intermediate size, like the moon at an intermediate altitude, because their distance from the eye is intermediate. The same effect will be equally well seen by placing three small wafers of the same size and colour on the square summits of the drawings of the quadrangular pyramids, or more simply, by observing the larger size of the square summit of the hollow pyramid.

This explanation of the cause of the increased size of the horizontal moon is rigorously correct. If any person should suspect that the circles which represent the moon are unequal in size, or are at different distances from the eye, they have only to cut the diagram into three parts, and make each drawing of the frustum of the cone occupy a different place in the binocular slide, and they will obtain the very same results. Hence we place beyond a doubt the incorrectness of Dr. Berkeley’s theory of the size of the horizontal moon,—a theory to which the stereoscope enables us to apply another test, for if we make one or more of these circles less bright than the rest, no change whatever will be produced in their apparent magnitude.