The Theory of Emulsions and Their Technical Treatment. By William Clayton, Hon. Secretary to the British Association Committee on “Colloid Chemistry and Its General and Industrial Applications.” F. G. Donnan, Chairman of the British Association. Committee on “Colloid Chemistry and Its General and Industrial Applications.” Second Edition. 300 pages with 42 illustrations. P. Blakiston's Son & Co., Philadelphia, Pa., Publishers. Price $4.50