216 BRIDGMAN. 



The range in values is very striking, being almost two and a half fold. 

 The difference between the figures for the ordinary and the unicrystal- 

 line easting tends to be the extreme. This is as one would expect, 

 because the manner of chilling would tend to make that surface which 

 grows along the axis of the unicrystalline cylinder grow at right angles 

 to the exterior curved surface in the simple casting, advancing along 

 the radius. 



The initial compressibility at 20° of cadmium of density 8.60 was 

 found by Richards to be 21 X 1(H. A. W. J. found for the initial 

 compressibility 22.2 X 10 -7 , and for the average compressibility to 

 10000, 19.2 X 10~ 7 . This pressure coefficient of compressibility is at 

 the extreme edge of the values found above, but the initial compressi- 

 bility of these two observers is outside the range above, which would 

 mean a greater variation of compressibility with direction than is sug- 

 gested by my measurements. 



Zinc. All the specimens were made from melting point samples of 

 the Bureau of Standards of the following analysis: Pb 0.0026, Cd 

 0.0022, Fe 0.0034, Cu (not detected), Zn (by diff .) 99.992. More elabo- 

 rate measurements were made on this than on any other metal, and 

 the results show a greater effect of crystal structure. In general the 

 results were much more irregular than for any other metal; there 

 were more likely to be permanent distortions after the first application 

 of pressure, there was quite often hysteresis, and the relation between 

 pressure and deformation did not depart regularly from linearity, but 

 on several occasions curves were found with distinct points of inflec- 

 tion. (The total departure from linearity of these abnormal cases 

 was never large.) It will not pay to describe in detail all the anomal- 

 ous effects found, but I will give merely the average compressibility 

 between and 12000 kg. at 30°. The effect of temperature was 

 studied in only one or two cases. 



With the preliminary apparatus measurements were made on three 

 different samples. The first of these, a casting, had an average com- 

 pressibility between and 12000 kg. of 24 X 10" 7 , the second, an 

 extruded casting, had a mean compressibility of 12.8 X 10 -7 , and the 

 mean compressibility of the third, also an extruded casting, was 

 10.7 X 10~ 7 . Measurements with the final form of apparatus and 

 another simple casting gave for the mean compressibility 9.04 X 10 -7 , 

 and on an extruded casting 8.58 X 10 -7 . The density at 20° of the 

 simple casting was 7.129, and of the extruded casting 7.134. 



Finally a unicrystalline casting was made by the procedure described 

 under cadmium, and measurements made of the compressibility of 



