Referee's report by Cecil Edgar Tilley, on a paper 'Isomorphous replacement and superlattice structures in the plagioclase felspars' by S H Chao and W H Taylor Sectional committee: Physics Recommended for publication in Proceedings, in full. The works an advance of the author's previous work, as the composition of the structures has been defined. The paper is an improtant contribution to the subject and is 'clearly written, concise and the arguments logically developed. [Published in Proceedings of the Royal Society A, 1940]. Date received not given. 13 May 1940