IRON AND STEEL 55 



and in recent times other methods for measuring 

 industrial high temperatures have been evolved and 

 perfected. But the highest service which Le 

 Chatelier's thermo-couple has rendered has been 

 as an instrument for purely scientific investigation, 

 as an aid to that study of the structure and con- 

 stitution of metals and alloys which was rendered 

 possible by the advent of the microscopic examina- 

 tion of metals. 



Having seen how the new methods of studying 

 metals originated, we may now consider what is 

 the kind of new knowledge about metals which 

 the application of these methods has revealed. 

 This we can attempt only in the broadest outline, 

 since the new science already constitutes a subject 

 of such magnitude that the workers in it are finding 

 it necessary to specialise upon some part of its field. 

 It must be stated at the outset, too, that this is 

 not a case in which the subject was first allowed 

 to develope on purely scientific lines, but that at 

 every stage attempts were made to apply and 

 utilise in practice the results obtained in the 

 laboratory. There can be no doubt that the 

 development of the whole subject was to some 

 extent hindered, both on the practical and the 

 scientific side, by some of these premature attempts. 

 As it happens, that metal which from the practical 

 point of view stands in importance so far above 

 all others iron is also the most difficult and 

 complex to deal with from the point of view of the 



