LESLIE AITCHISON AND F. ATKINSON 



155 



the form of the curve which might reasonably be expected. Here 

 again there is surely some constitutional alteration taking place, and it 

 might reasonably be hoped that a sufficiently high powered Microscope 

 would reveal it. 



The theory which has probably had as much effect as any other 

 upon recent scientific metallurgy is that known as the " amorphous 

 cement " theory. This theory postulates the existence, between the 

 crystals of a metal, of a thin layer of amorphous material which both 



Table 2. 



separates and binds together the individual crystals. The properties of 

 this amorphous metal are necessarily different fi"om those of the 

 crystals which it surrounds. The evidence for the existence of this 

 layer is largely circumstantial, and though the evidence is powerful 

 it would be decidedly stronger if the cement could actually be revealed. 

 If a power of 10,000 failed to produce any further evidence of its 

 existence it would seem difficult to imagine that it is really there . 



Duralumin is a metal which has distinctly peculiar properties. If 

 duralumin be quenched in water from a suitable temperature it is soft 

 at first, but after standing for a time, e.g., 24 hours, the metal becomes 

 quite hard. This change of properties is bound to be accompanied by 

 some change of constitution, and a possible explanation of this change 

 has recently been put forward by Dr. Jeffries. It seems certain, how- 

 ever, that the application of higher powers of microscopic examination 

 would help materially in the investigation of this problem. 



