horizontal axis; the second is for tilting it at an angle with the horizon; the third is for turning it about a vertical axis; and the fourth for raising and lowering it through a range of several inches.
When a prism like that shown in Fig. 9 is interposed in the path of a narrow beam of sunlight, admitted into a dark room, its alteration
| Fig. 10. | Fig. 11. |
 | |
| Equilateral Prism. | Prism mounted on Stand. |
of the direction of the ray is easily seen, and it will be found that the course of the light is altered, by refraction, some 40° or 50° from its original course.
The properties of light, to which we have here briefly referred, are interesting in themselves, and important to be known; but they have additional interest as preparing for an understanding of spectrum analysis, which will be taken up and popularly explained in future numbers of the Monthly.
| SYNTHETIC CHEMISTRY. |
By Prof. JOHN W. LANGLEY,
OF THE WESTERN UNIVERSITY, PENNSYLVANIA.
CHEMISTRY has been called the analytical science, and undoubtedly with justice in the past, since the most exact processes with which it deals are still those which go technically by the name of analysis; but, of recent years, the arts have been enriched by many perfumes, colors, and drugs, which are the results of careful and
