XETT BOOKS C o n d u c t ~ o nof Electrzcity Through Gases. By SIR J. J. THOMSOK AND G. P. THOMSON. Third edition, Volume 11. 608 pp. Cambridge: Cambridge I'niversity Press, 1933. New York: The MacMillan Company, 1933. Price: $6.50. The volume treating ionization by collision and gaseous discharge completes the third edition of this well-known work originated by Sir J. J. Thomson. I n spite of, or rather because of, the vast amount of material dealt with, the reviewer gets the impression t h a t this, the third edition, cannot occupy the commanding position which the first edition did thirty years ago in the then much newer and ' narrower field of electrical discharge in gases. This is not meant as a criticism of the admirable compilation. The field presents so many possibilities and complexities that it has expanded enormously in various directions, experimental and theoretical. It is no longer possible t o give equally adequate treatment t o all the phases of the subject in the compass of two volumes. The task is not rendered easier by the fact that physics has been making major advances along a broad front with such rapidity t h a t the conquered terrain has not yet been properly cleared up and unified in a way t h a t makes a complete survey possible. The volume is written in a clear readable style. The figures and tables are well presented. The first two chapters are devoted to cathode rays, the second t o their wave properties, the third t o electron collisions, the fourth and sixth respectively t o ionization by positive ions and by x-rays, the fifth t o reflected and secondnry electrons from solids, the seventh t o ionization by chemical reaction, the material of which is little changed from the earlier edition. Chapter VIII, of more than one hundred and fifty pages, deals with the various phenomena of gaseous discharge a t low pressure. Chapters I X and X deal with the spark and the electric arc. s. c. LIXD. T h e Physico-chemical Properties of Plant S a p s in Relation to Phytogeography. Data o n Natike Vegetation in i t s Natural Environment. By J. ARTHURHARRIS,late Head of the Department of Botany, University of Minnesota. Formerly Resident Botanist, Station for Experimental Evolution, the Carnegie Institution of Washington. 13.5 X 23.5 cm.; vi 339 pp. Minneapolis: The University of Minnesota Press, 1934. Price: $4.50. From about 1912 until his death in 1930 one of Dr. Harris' major projects was t h e investigation of the relationship which existed between the physicochemical properties of the leaf tissue fluids of plants and the ecological environment characteristic Qf the plants. He devised methods and apparatus suitable for the carrying out of physicochemical technics in field laboratories, and established his laboratories in t h e field where plants could be studied in their native habitats. Extensive studies ere carried out on the mesophytic plants of Long Island, N. Y., the coastal plains a n d sand dune areas of North and South Carolina and the Island of Jamaica, the Dismal. Swamp in Virginia, the Everglades and coastal swamps of Florida and Georgia, t h e rain forests of Jamaica and Hawaii, and the deserts, mountain slopes, arroyos, salt flats, lava fields, dunes, etc., of Arizona, Utah, California, Colorado, Washington, and Hawaii. Altogether sixteen seasons were spent in the field studies. Fragments cf the data were published by Dr. Harris from time t o time but the great masses of 987
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