Page:Popular Science Monthly Volume 17.djvu/128

118 one on the "Theory of Rolling Curves," and the other on the "Equilibrium of Elastic Solids."

During his college course in Cambridge he developed the germs of his future important work on electricity and magnetism, in a paper on "Faraday's Lines of Force," and five other papers on the same subject were contributed by him to the "Philosophical Magazine" during 1861 and 1862. Only a few months after obtaining his Cambridge degree in 1854, he contributed to the Cambridge Philosophical Society a remarkable paper on the "Transformation of Surfaces by Bending." In 1857 his paper on the "Motions of Saturn's Rings" obtained for him the Adams prize in the University of Cambridge. He received in 1860 the Rumford medal from the Royal Society for his "Researches on the Composition of Colors" and other optical papers. The subject of color Professor Maxwell has treated with great success, both experimentally and theoretically, his papers on the subject extending from 1855 to 1872. His important paper on a "Dynamical Theory of the Electro-magnetic Field," in which he endeavored to explain electric and magnetic forces by means of stresses and motions of the medium, and thus do away with the notion of action at a distance, was read before the Royal Society in 1864, and printed in the "Transactions" of that year. His contributions to the Kinetic theory of gases form one of the most important and valuable of his investigations. His first paper on this subject appeared in the "Philosophical Magazine" of 1860, and he at different times since published various others. Before him, Clausius had made a great advance by his explanation by this theory of the relation between the volume, temperature, and pressure of a gas, the cooling of it by expansion, and the slowness of diffusion and conduction of heat in it. An investigation was also made by him of the relation between the length of the mean free path of a particle, the number of particles in a given space, and their least distance when in collision. Maxwell by an investigation of the collisions of a number of perfectly elastic spheres, first when they are all of the same mass, and then when they are of different masses, reached the law of Gay-Lussac, that in a unit of volume there is the same number of particles in all gases when at the same temperature and pressure. He also explained gaseous friction, and showed that the coefficient of viscosity is independent of the density of the gas. The approximate length of the mean free path was first deduced by him from data furnished by Stokes.

Pursuing the same subject, he made a few years later a valuable series of experimental investigations on the viscosity and internal friction of air and other gases, the results of which were brought to the attention of the Royal Society in 1866. A paper on "A Method of making a Direct Comparison of Electrostatic with Electro-magnetic Force, with a Note on the Electro-magnetic Theory of Light," was also presented to that body in 1868. He took great interest in graphical