As "Science" is the investigation and knowledge of principles, so an "art" may be defined as a system of means, in accordance with these principles, for attaining some special end. Teaching is one of the arts; and it depends as entirely for its success upon a right application of the principles of the science of education, as the art of dying does upon the principles of chemistry. As an art, therefore, teaching must be subjected to all those laws which regulate the improvement of the other arts, and without which it can never be successfully carried on, far less perfected. These laws are now very generally understood; and we shall briefly advert to a few of them, which are necessary for our present purpose, and endeavour to point out their relation to the art of teaching. 1. One of the first rules connected with the improvement of the arts is, that the artist have _a specific object in view, for the attainment of which all his successive operations are to be combined_.--The manufacturer has his _cloth_ in prospect, before he has even purchased the wool of which it is to be composed; and it is the desire of procuring cloth of the most suitable quality, and by the easiest means, that compels him to draw liberally and constantly from the facts ascertained, and the principles developed, by the several sciences. From the science of mechanics he derives the various kinds of machinery used in the progressive stages of its production; and from the science of chemistry he obtains the processes of dying, and printing, and dressing. But he never troubles himself about the science of mechanics or of chemistry in the abstract; he thinks only of his cloth, and of these sciences as means to assist him in procuring it. He is careful of his machinery, and is constantly alive to the mode of its working, and is thus prompted to adopt such improvements as observation or experience may suggest; but it is not the machinery of itself that he either cares for, or thinks about. No; it is still the cloth that he keeps in view; and his machinery is esteemed or slighted, adopted or abandoned, exactly in proportion as it forwards his object. The processes necessary in the different departments of his establishment, are complicated and various, and to a stranger they are both curious and instructive; but it is neither the labour nor the variety that he is seeking. His is a very different object; and of this object he never loses sight; for the varied operations of stapling and carding, of spinning and weaving, are nothing more than means which he employs for accomplishing his end. He knows the uses of the whole complicated operations; and he sees at a glance, and can tell in a moment, how each in its turn contributes to the great object of all,--the production of a good and marketable cloth.