AT the recent meeting of the Iron and Steel Institute Messrs. A. Westgren and G. Phragmen presented a continuation of work published by them two years ago at the same Institute. The present paper deals with the crystal structure of? iron, the crystal shape of Cementite, and the structure of Austenite. In their previous paper a series of powder photograms of?,?, y and? forms of iron was reproduced. At that time all attempts to get a photogram of? iron (stable only above 14000 C.) in the pure state had failed. Its interference lines were mingled with tjhose originating from y iron. By improved heating arrangements it has been possible to obtain a more uniform temperature, and the new photograms are quite free from y interferences and confirm the conclusion previously drawn, namely, that? iron has the same lattice structure as? and? iron.