SIR R. HADFIELD AND MR. T. G. ELLIOT, F.I.C. 157 



its Alloys, including in that term the material generically known as 

 " Steel," to be examined and understood in a manner which was 

 before not possible. " Steel " is a wide term and to-day covers 

 material w^hich is practically pure Iron, for example, products contain- 

 ing 99.9 per cent, of Iron w^hich offer high resistance to corrosion and 

 oxidation and containing practically no Carbon, up to the material 

 used for wortle or drawing plates which contain even more than 2 

 per cent, of Carbon. 



Twenty-five years ago there were scarcely half-a-dozen Steel 

 Works in the country which could lay claim to the possession of 

 a Microscope suitable for metallographical examination. At the 

 present time it may be safely said that no steel works of any size is 

 without one. Nor is the use of the Microscope confined to the ex- 

 amination of Iron and Steel sections, for those engaged in the investiga- 

 tion of non-ferrous metals and alloys find its aid equally useful. 



The history of Metallography, short as it is, is beyond the scope of 

 the present paper. Naturally such history to be complete would 

 record the improvements w^hich have taken place in the construction 

 of Lenses for metallographic work. One of the most important of 

 these was the introduction of the Apochromatic Objective by means 

 of W'hich increased resolution was obtained, an absolute necessity for 

 successful high power photomicrography. Unfortunately, as this 

 Country had occasion to find out on the outbreak of War, the making 

 of these objectives has in the past been largely in foreign hands. Steps 

 are being taken to remedy this, and there is every reason to hope that 

 here, as in other directions, in future, we shall be rendered entirely 

 independent of the foreigner. 



Great as have been the advances made in the microscopical ex- 

 amination of Iron and Steel, there still remains a wide field for 

 exploration ; for example, as regards methods w^hich wdll enable increased 

 magnifications to be obtained. It is w^onderlul what can be accom- 

 plished by the aid of the human eye alone, and even to-day the finest 

 quality of crucible cast steel is, in its ingot form, first packed or sorted 

 over in this manner. It is stated that an experienced workman can, 

 hy the eye, detect from the appearance of the fracture differences as 

 small as .05 per cent, to .10 per cent, of Carbon. No doubt for many 

 purposes an ordinary strong magnifying glass will tell much and 

 more than the unaided eye can do, but when it is desired to reveal 

 structures minutely, then the microscope is called in with great 

 advantage. Magnifications of 10 or less, upwards to 1,000 or 1,500 

 are those most commonly used in metallography. Photomicrographs 

 of larger magnifications than 1,500 have been rarely published. The 

 Authors have, however, carried out experiments in* order to obtain 

 photographs of 5,000 and even 8,000 magnification, w^hich may be of 

 interest to this Society. 



The very fine structures met with in alloy steels have made it 

 .•desirable and induced the Authors to prepare in their research 

 photomicrographs at higher magnifications than have hitherto 

 been obtained. With great care and attention to necessary details, 

 particulars of .w^hich are described in this Paper, we have been able to 



