COMPRESSIBILITY OF METALS. 215 



same way, the appearance of the casting indicated almost unescapably 

 the similarity of the crystalline orientation throughout the mass. At 

 any rate, this method of casting seems to offer important possibilities, 

 and has at least brought out great differences in compressibility. A 

 casting made in this way I shall call a "unicrystalline" casting. 



Regular runs were made on the first two samples of cadmium at 30° 

 and 75°; on the third a run only at 30° was made. The results with 

 these castings of cadmium had as a rule more error than the other 

 compressibility measurements; the irregularity is probably a real 

 phenomenon, and may be due to a slipping of the crystalline grains 

 under pressure. In one case the permanent deformation after the 

 initial application of pressure was considerably greater than for most 

 other metals. 



For the simple casting of Eimer and Amend cadmium the average 

 arithmetical departure from a smooth curve of the 27 observed points 

 (no discards) was 0.29% and the maximum deviation from linearity 

 was 2.28% of the maximum pressure effect. For the extruded casting 

 of Eimer and Amend the arithmetical departure from smoothness 

 (five discards) was 0.44% and the maximum deviation from linearity 

 2.33%. The unicrystalline casting of Kahlbaum's cadmium at 30° 

 (one discard) gave the figures respectively 1.8% and 2.03%. The 

 results calculated from these different specimens, assuming equal 

 compressibility in all directions, are: 



Eimer and Amend, simple casting, 



AV 



At 30° -- = - 10- 7 (19.54 - 10.7 X 10" 5 p) p 



V 



AV 

 At 75° — = - 10- 7 (20.19 - 11.0 X 1Q- 5 p) p . 



I 



o 



Eimer and Amend, extruded casting, 



FA 

 At 30° — = - 10- 7 (14.17 - 7.5 X 10-*p) p 



V 



AV 

 At 75° — = - 10- 7 (14.53 - 7.7 X 10- 5 p) p . 



> 



Kahlbaum's, unicrystalline casting, 



AV 

 At 30° — = - 10- 7 (8.57 - 3.8 X 10" 5 p) p . 



Y0 



