2 
Transactions of the Society. 
etched revealed a characteristic structure visible even to the naked 
eye. It was the work of Dr. Sorby, of Sheffield, however, that 
practically inaugurated the new era in the Science of Metallurgy. 
This great Englishman was the first to undertake the systematic 
study of the structure of metals by means of micrographic examina- 
tion, and he was followed some fourteen years later by Prof. 
Martens. The work of these pioneers was quickly recognized, 
with the result that the study of physical metallurgy was taken 
up and extended by Osmond, Howe, Le Chatelier, Roberts-Austen, 
Stead and many others. The progress has been so great during 
the last forty years that at the present time most engineering firms 
of repute have at least one member of the staff fully qualified to 
carry out a thorough micrographic examination of the metals and 
alloys used in the industry. 
The object of the present paper is to show the importance of 
the Micro-Examination of Metals and Alloys, and some of the 
directions in which the microscope is used in connexion with the 
Metal Industry. 
The field of application is fairly considerable at the present 
time, and is. rapidly extending; it includes, amongst others, the 
determination of : — 
1. The presence of foreign bodies. 
2. The existence of small quantities of metals, metalloids, etc., 
which may or may not exert an injurious effect on the 
materials. 
3. The constitution of the alloy. 
4. The uniformity with which the constituents are distributed 
throughout the metallic mass. 
5. The effect of stresses, such as those set up by cold working. 
6. Crystalline form and size of crystals. 
7. The results of heat treatment. 
8. The presence of mechanical and physical defects. 
As it will be impossible as well as inadvisable to attempt to 
deal with all the points just named, if this contribution is to be 
EXPLANATION OF PLATE I. 
Fig. 1. — Iron-phosphide eutectic, x 1000. 
Fig. 2. — Pure silver, x 100. 
Fig. 3. — Pure gold, x 100. 
Fig. 4. — Silver p 1*2 p.c. platinum, x 100. 
Fig. 5. — Silver + 2 p.c. iridium. Section, x 50. 
Fig. 6. — Silver + 0*01 p.c. rhodium, x 15. 
The magnification as given refers to the original photomicrographs. The 
illustrations have been reduced and are at a magnification equal to f^ths of the 
figures given. 
