UNTIL recently, there was a serious lack of really representative books dealing with the theory and practice of the photoelectric and selenium cells. Happily, this no longer exists, thanks to Dr. Campbell and Miss Ritchie—whose exhaustive book is already in its second edition—and to Mr. G. P. Barnard, whose recent treatise on the selenium cell, though perhaps not so critical a survey of the subject as it might have been, will certainly be regarded as a standard reference work.
Photocells and their Application.
Dr. V. K. Zworykin Dr. E. D. Wilson. Pp. xi + 209. (New York: John Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1930.) 12s. 6d. net.