A CATALOGUE OF BRITISH SCIENTIFIC AND TECH- NICAL BOOKS. (British
Science Guild. 12s. 6d.) A COMMITTEE appointed by the British Science Guild is responsible for the preparation of this useful work of refer- ence. The completeness of the work (which is confined to
books still in print) may be estimated from the number of titles given under the headings " Relativity " (more than thirty) and " Wireless Telegraphy " (over fifty), which we have selected at random.