[15] The Psychology of Peoples. By Gustave Le Bon. New York: The Macmillan Company. Pp. 236. Price, $1.50. [16] A Text-Book of Mineralogy, with an Extended Treatise on Crystallography and Physical Mineralogy. By Edmund Salisbury Dana. New edition, entirely rewritten and enlarged. New York: John Wiley & Sons. Pp. 593. $4. [17] The Story of the Railroad. By Cy Warman. New York: D. Appleton and Company (Story of the West Series). Pp. 280. Price, $1.50. [18] Infinitesimal Analysis. By William Benjamin Smith. Vol. I. Elementary; Real Variables. New York: The Macmillan Company. Pp. 352. $3.25. [19] The Jubilee History of the Leeds Industrial Co-operative Society from 1847 to 1897. Traced Year by Year. By George Jacob Holyoake. Leeds (Eng.) Central Co-operative Office. Pp. 260. Fragments of Science. =The Nernst Electric Lamp.=--Prof. Walter Nernst, of the University of Göttingen, has recently devised an electric lamp which promises to be an important addition to our present methods of lighting. The part of the lamp which emits the light consists of a small rod of highly refractory material, said to be chiefly thoria, which is supported between two platinum electrodes. The rod is practically a nonconductor when cold, but by heating it (in the smaller sizes a match is sufficient) its conductivity is so raised that a current will pass through it; after the current is once started the heat produced by the resistance of the rod is sufficient to keep up its conductivity, and the latter is raised to a state of intense incandescence, and gives out a brilliant white light. As the preliminary heating by means of a match or other flame would in some cases be an inconvenience, Professor Nernst has devised a lamp which, by means of a platinum resistance attachment, can be started by simply turning a switch. The life of the rods is about five hundred hours. The lamps are said to work equally well with either alternating or direct currents, and there is no vacuum necessary. If this lamp proves a success as a commercial apparatus, it will be but another example of how slight a matter may make all the difference between success and failure. There have been numerous experimenters trying for the last ten years, and in fact ever since the appearance of the arc lamp, to utilize in an electric lamp the great light-giving power of the refractory earths in a state of incandescence; but, owing to their high resistance at ordinary temperatures, no results were obtained until Professor Nernst thought of heating his thoria rod, and this simple procedure seems to have solved the whole difficulty. It is claimed that the Nernst lamp is a much more economical transformer of electricity into light than the present incandescent electric lamps. An apparatus called a kaolin candle, which has been suggested as an anticipation of Professor Nernst's lamp, was constructed by Paul Jablochkoff in 1877 or 1878. It consisted of a strip of kaolin, along which ran a "match" of some