The second object of descriptive geometry, is to deduce from the exact description of bodies all that necessarily follows of their forms and their respective positions; in this sense it is a means of seeking truth, as it offers perpetual examples of the passage from what is known to what is unknown, and as it is always applied to objects susceptible of the minutest evidence, it is necessary that it should form part of the plan of a national education. It is not only fit to exercise the intellectual faculties of a great people, and to contribute thereby to the perfection of mankind, but it is also indispensable to all workmen, whose end is to give to certain bodies determined forms, and it is principally owing to the methods of this art having been too little extended, or in fact almost entirely neglected, that the progress of our industry has been so slow. We shall contribute then to give an advantageous direction to national education, by making our young artist familiar with the application of descriptive geometry, to the graphic constructions which are necessary in the greater number of the arts, and in making use of this geometry in the representation and determination of the elements of machinery, by means of which, man by the aid of the forces of nature, reserves for himself, in a manner, in his operations no other labour than that of his intellects. It is no less advantageous to extend the knowledge of those phenomena of nature which may be turned to the profit of the arts. The charm which accompanies them will overcome the repugnance that men have in general for manual operations, (which most regard as painful and laborious,) as it will make them find pleasure in the exercise of their intellect; thus there ought to be in the formal school a course of descriptive geometry. As yet we have no well compiled elementary work on that art, because till this time learned men have taken too little interest in it, or it has only been practised in an obscure manner by persons whose education had not been sufficiently extended, and were unable to communicate the result of their lucubrations. A course simply oral would be absolutely without effect. It is necessary then, for the course of descriptive geometry, that practice and execution be joined to the hearing of methods; thus pupils will be exercised in graphic construction of descriptive geometry. The graphic arts have general methods with which we can only become familiar by the use of the rule and compass. Among the different applications that may be made of descriptive geometry, there are _two_ which are remarkable, both for their universality and their ingenuity; these are the constructions of _perspective_ and the strict determination of the _shadows_. These two parts may finally be considered as the completion of the art of describing objects. R. BROWN. * * * * * AN IDLER'S ALBUM; OR, SKETCHES OF MEN AND THINGS. THE RADIANT BOY.