AT the autumn· meeting of the Iron and Steel Institute held in September at the British Empire Exhibition, Wembley, an account was given by Dr. Rosenhain and some of his colleagues of an investigation of the alloys of iron which was begun by them rather more than a year ago under the auspices of the Ferrous Alloys Research Committee, which is the successor of the Alloys Research Committee of the Institution of Mechanical Engineers. The new Committee contains representatives of the Royal Society, the Institutions of Civil Engineers, Mechanical Engineers, Electrical Engineers, Naval Architects, and Mining and Metallurgy, and the Iron and Steel Institute. Under the auspices of this Committee, and with the concurrence of the Advisory Council of the Department of Scientific and Industrial Research, a beginning has been made upon a programme of work which is more ambitious, more difficult, and more expensive than anything which has hitherto been attempted. As Dr. Rosenhain points out in his introduction (Part I.) to the research, in spite of the large amount of scientific research devoted to the alloys of iron, much fundamental knowledge as to the constitution of the binary systems is still lacking. Most of the alloys hitherto investigated contain some carbon in addition to the special alloying metal, and this may, and probably does, have a profound influence on the equilibrium in question. Many of the most important industrial alloys contain three or more elements, and their composition has been arrived at largely by empirical methods. The precise influence of any particular element is largely a matter of guess-work. For this reason it is eminently desirable that the equilibria of the binary systems should be determined with the purest materials and the highest accuracy possible.