Among the improvements which have been recently introduced into schools, that of illustrating the sciences by means of simple and appropriate apparatus, deserves to be particularly noticed. Apparatus for the illustration of the sciences has long existed in colleges, and no institution of the kind would be thought worthy of patronage, which did not possess it. But apparatus is not more necessary in colleges, than is appropriate apparatus in schools. Indeed, from the nature of the case, it would seem to be more necessary in schools than in colleges. Children and youth, in the earlier stages of their education, are naturally volatile, and need something to fix their attention. They are less accustomed to abstract reflection than persons of a more advanced age, and therefore have greater need of a visible illustration of the sciences. Apparatus for schools needs to be materially different from that usually found in colleges, which is generally so expensive, as to be altogether beyond the reach of ordinary schools. Apparatus for schools must be cheap, or it will not be generally introduced; it must be neat, or scholars will turn away from it with disgust, and science will be disgraced by its slovenly appearance; it must be scientific, or it will be good for nothing. It may be scientific without being expensive. The value of a machine for scientific illustration depends much more upon its peculiar construction, than upon its mechanical execution. By the use of apparatus, two avenues are opened to the mind where but one existed before, and the eye becomes auxiliary to the understanding, in the acquisition of knowledge. Appropriate apparatus is alike calculated to illustrate the sciences, and deeply to impress their principles upon the memory. Some kinds of apparatus have long been found in schools. Geography has long had the aid of maps, and no teacher would use a geography which was not furnished with a respectable atlas. But maps alone are not a sufficient apparatus in teaching geography. A globular revolving map of the world, a globe, and a cylindrical revolving Mercator's chart, will furnish important aid in explaining the globular, polar, and Mercator's projections of a map of the world. Astronomy and natural philosophy can no more be successfully taught without the use of machines, than can geography without the use of maps. No text-book on these subjects would be thought fit for use, which was not furnished with plates and diagrams. But plates and diagrams are but an inferior kind of apparatus; the objects which they represent are extensively presented in perspective, and the coarse manner in which these plates are executed, as well as the intrinsic difficulties of the subject, render them but imperfect substitutes for machines and models for illustration. The great leading principles of descriptive astronomy may, by means of a cheap machinery, be made matters of ocular demonstration, and thus be rendered intelligible to children.