Helmholtz's treatise on physiological optics: Translated from the third German edition. Edited by James P. C. Southall, Columbia University. Vol. II, The Sensations of Vision. viii–480 pages, colored plates and illustrations in the text, large 8vo. The Optical Society of America, 1924. Price, $7. This work is not obtainable from booksellers but only through the Optical Society of America. Applications for purchase must be addressed to Prof. F. K. Richtmyer, Cornell University, Ithaca, N. Y.