MR. DE TUNZELMANN, in writing a popular account of wireless telegraphy, has attempted the double task of describing its historical development and of giving an account, which shall be intelligible to the lay reader, of the fundamental principles of the subject. The descriptive parts are based mainly on the papers which have been read by Mr. Marconi, and explain in an interesting manner free from superfluous detail the system which he has worked out. It is to be regretted that the work of other experimenters is hardly adequately recognised; Prof. Slaby, for example, deserves more than the half dozen lines allotted to him. Moreover, such information as is given is easily accessible in Mr. Marconi's published papers, whereas a careful comparison of the systems devised by the various workers would be a valuable addition to the literature of the subject.
By G. W. de Tunzelmann. Pp. iv + 104. (London: Office of Knowledge, 1901.) Price 1s. 6d.