848 POPULAR SCIENCE MONTHLY. 



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 api^earance of Mars, its size, 

 orbit, etc. From measurements made at Flagstaff, the diameter of the 

 planet was determined as 4,315 miles, and its polar flattening as ^ws 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 disappeai'ed altogether. This was the occur- 

 rence 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 u^son 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 Technol- 

 ogy* consists of chapters by vai'ious 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 Mcx^rthur. 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 distilla- 

 tion 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 em- 

 ployed 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 



* Chemical Technology. Edited by Charles Edwari Groves and William Thorp. Volume 11, 

 Lighting. Pp. 398, large 8vo. Philadelphia : P. Blakiston, Son & Co. Price, $4. 



