Plastic Crystals of Ammonium JSitrate. 5 



■directly proportional to the 'stress, but increases more rapidly 

 with increase of stress. Indeed, in subsequent experiments, 

 loads that were not very much smaller than those which 

 produced fairly rapid deflexion, produced exceedingly slow 

 motion. 



1-0 



Fitr. 5. 



4fe^ 



m 



ft 



Length I s 3-0 cms 

 Dejatb d=-27cms 

 Breadth b='29cm< 



^L 



20 



40 



60 



80 



100 



120 



140 160 Hours. 



There is a slight unbending when the load is removed, 

 showing that the crystal is slightly elastic, but most of the 

 bending is permanent. 



The 40 grams load produced more rapid bending than the 

 50 grams first applied. This must be due to the previous 

 history being different in the two cases. The 40 grams, it 

 will be noticed, is applied just after the 100 grams, and there 

 may be a slow return still taking place. On again removing 

 the load, it is seen that there is an elastic return. The 

 70 grams load produced a rate of deflexion of about the 

 value that might be expected ; but produced fracture in the 

 •crystal at the clamp, the point of maximum strain. 



The results of these experiments show that the bending is 

 at first rapid after applying a load. Then it approaches 

 more nearly a constant rate ; finally either rapidly breaking, 

 or, perhaps in some cases of small load, tending to a limiting 

 value. The rate of bending increases rapidly with increased 

 load, being by no means proportional to the load. Further. 

 a small elastic return is indicated. 



Since the clamping of the crystal must produce unknown 



