THE ninth volume of the Carnegie Scholarship Memoirs of the Iron and Steel Institute contains an account of an investigation on the above subject by Messrs. Whiteley and Hallimond, of the South Durham Steel and Iron Co. The research arose out of an observation made in the course of experiments in connection with the Eggertz test for combined carbon made by one of the authors. On examining the composition of the gases evolved when samples of steel were dissolved in dilute nitric acid, the authors noticed that the nitrous gases given off differed considerably in their proportions in the case of different samples. They were at first inclined to think that these variations were due to the influence of other elements, such as carbon and phosphorus, which are always present in steels. Later work, however, showed that the chief cause of the variations was the particular mechanical treatment to which the different samples have been subjected.