THE STRUCTURE OF METALS 211 



appear to be impossible that such pressures could be confined 

 to the solid crystals. 



The importance of a microscopical control of engineering 

 and structural materials will be obvious, even from this hasty 

 and incomplete sketch of the relation between structure and 

 properties. Whilst ultimate chemical analysis is of great 

 importance in controlling materials, there is much necessary 

 information that cannot be obtained by such means. Proximate 

 chemical analysis, which in some cases affords valuable informa- 

 tion, is almost in its infancy. Its absence is in a large measure 

 supplied by microscopical analysis, which permits a visual 

 separation of constituents. The highly important question 

 of crystalline arrangement within the metal is only to be 

 approached by microscopical means and although the complete 

 correlation of structure with mechanical properties may be 

 only an ideal towards which workers in metallography are 

 striving, the knowledge already available on this subject 

 suffices to make the microscope an indispensable auxiliary of 

 the balance and the testing machine in metallurgical work. 



