Page:Popular Science Monthly Volume 19.djvu/134

124 heating and efficient ventilation of the buildings. It begins with the consideration of the site and the digging of the well, and closes with the elevations and finishings of the schoolhouses. An article on log schoolhouses is added. Circular No. 5 is a statement of the working of the English education act of 1870 in districts outside of cities, prepared for the department, by Mr. Henry W. Hulbert.

these chapters Mr. Sawyer has given a résumé of the present condition of electric lighting by incandescence, describing the chief apparatus that has been so far devised. He begins his exposition with a consideration of the various electric generators, as these necessarily are at the foundation of any system of electric lighting. Of these the two important classes are those of the Gramme type, in which he includes those of Maxim and Brush; and those of the new Siemens type, in which he places his own and Edison's. The Wilde, De Meritens, and Lontin machines are also described, the first being characterized as the "germ of a perfect generator," in that in it the intensity of the magnetic field is uninfluenced by the resistance of the external circuit, and a larger part of the entire current can therefore be used than in accumulative machines. The review of incandescent lamps includes those of Starr and King, Lodyguine, Konn and Kosloff, Bouliguine, Fontaine, Farmer, Sawyer, Edison, and Maxim, in which the carbon is protected from the atmosphere, and those of Reynier and Werdermann, in which it burns in the air. Of the former, only the last three are regarded as practicable lamps, and of these the Maxim is considered as, in all essential particulars, a duplication of that of Edison. With regard to the duration of the carbon, Mr. Sawyer holds that the hope of making it permanent is chimerical, as no material will stand the strain to which an incandescent conductor is subjected, and that the part of wisdom, therefore, is to provide for its renewal. In treating of the division of the current, four systems are considered—the series, the multiple, the multiple-series, and the series-multiple system. In the first, the lamps are strung one after the other upon one wire; in the second, each lamp is hung on a branch between two parallel wires; in the third, several lamps are placed upon a branch; and, in the last, groups or bunches of lamps are strung upon one wire. For a large number of lamps, Mr. Sawyer considers the first arrangement impracticable, and the last, which he has adopted, the most desirable. Regarding the cost of incandescent lighting, the conclusion is reached that it is not more than one seventh of that of gas for equal light, while the cost of plant, repairs, etc., will be much less. As to the future of incandescent lighting, and its relations to other forms of illumination, Mr. Sawyer expresses himself as follows: "The application of electricity to public and private illumination is a realization of the near future no longer to be questioned. It is not probable, however, that electricity will ever entirely supersede gas; indeed, it does not appear that illuminating gas has materially affected the consumption of illuminating oils. There is room, and will doubtless continue to be room, for all methods of artificial lighting, and it is not likely that, for many years to come, we shall witness anything more than the extensive use of electricity—public buildings and private residences, streets, and squares better illuminated than at present, and the new form of light keeping pace with the progress of older and well-tried institutions."

author's views are partly based on observations made among the different races of India. Ho supposes that lighter-colored peoples are developed from darker colored ones by a process of evolution which corresponds with the advance of civilization, and is promoted by the increasing habit of wearing clothing. The qualities which give a dark color to the skin are those which are necessary to preserve it against the inclemency of the elements. As clothing becomes more general, fuller, and more regularly worn, they become less important for protection, and are finally nearly obliterated.