Page:Popular Science Monthly Volume 48.djvu/938

848 months of 1894 and 1895, which included the time of the latest opposition of the planet. These observations were made from the Lowell Observatory, which was established at Flagstaff, Ariz., and Prof. W. H. Pickering and Mr. A. E. Douglass were associated with Mr. Lowell in making them. In this book Mr. Lowell gives first the general appearance of Mars, its size, orbit, etc. From measurements made at Flagstaff, the diameter of the planet was determined as 4,215 miles, and its polar flattening as of its equatorial diameter. The presence of an atmosphere is well established, and good fortune enabled measurements of it to be obtained. It appears that the atmosphere is thinner by half than the air upon the summit of the Himalayas, and in constitution does not differ greatly from our own. The ice cap about the south pole gradually dwindled away as the Martian summer advanced, and finally disappeared altogether. This was the occurrence—the first on record—which enabled the planet's atmosphere to be measured, and which gave additional information as to the presence and distribution of water upon its surface. Mr. Lowell gives us a notably full exposition of areography, or the geography of Mars, based upon a series of twelve views made by him, and reproduced in the book, which together represent the whole surface of the planet visible on the first of August. He describes its continents and peninsulas, its seas and gulfs, and especially its famous canals, which make Mars a very Holland of planets. These straight or evenly curved lines he deems it very probable are irrigating ditches, made to control the water from the annual melting of the polar ice caps, for there seems to be no other way of distributing the planet's scanty supply of moisture. Various other features of the present and probable future condition of Mars are set forth in this attractive volume. At the end we have a map of its whole surface on the Mercator projection, followed by a list of areographic names and a general index.

The second volume of Messrs. Groves and Thorp's Chemical Technology consists of chapters by various authors on the fats and oils used for illuminating, and on the lamps in which these substances are burned. The first section, in which the animal and vegetable illuminating substances are described, and the modes of testing them are given, is by William Y. Dent. The attitude of the uncultivated Britisher toward the United States is unpleasantly evident in several of this writer's remarks about American products. The methods and apparatus employed in the extraction of stearin from various fats, and for distilling and pressing it, are described by John McArthur. His text is accompanied with figures of the autoclaves of de Milly, Morane, and Droux, the apparatus of Tilghman, Hugues, and Michel for the decomposition of fats by water, two forms for the distillation of fatty acids, a hydraulic press for cold pressing, and one for hot pressing. L. Field and F. A. Field describe the making of candles from the material thus prepared, giving many illustrations of the machines employed in the industry. The largest contribution to the volume is made by Boverton Redwood, who furnishes the sections on petroleum and lamps, and, in conjunction with D. A. Louis, that on miners' safety lamps. Mr. Redwood gives brief accounts of the rise of the petroleum industry in the