522 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



of elasticity. It shows the impossibility of obtaining perfect elasticity 

 very much beyond the original elastic limit. This cylinder had been 

 previously seasoned for use in this work by subjecting it for some hours 

 to 28,000 kgm. The hole was then bored out from the original 7/16 

 inch to 1/2 inch. The 28,000 kgm. had produced a stretching at 



the inside from 7/16 inch to 

 perhaps 15/32 inch. Even 

 this high pressure did not 

 completely do away with 

 viscous yield at pressures 

 as low as 10,500. Another 

 interesting feature is the 

 approximate constancy of the 

 rate of yield over a pressure 

 range of 5000 kgm., from 

 10,500 to 15,500, as shown by 

 the fact that the low points 

 are nearly all the same dis- 

 tance below the correspond- 

 ing high points. This, too, 

 bears out an observation 

 made before, that elastic 

 after-effects, hysteresis, yield, 

 etc., are greater in larger 

 masses of metal. This cylin- 

 der was 4 1/2 inches o. d. 

 and 1/2 inch i. d. No such viscous yield was found in the cylinder 

 with which the change of volume of mercury was measured up to 11,000. 

 This cylinder was 3 inches o. d. and 9/16 inch i. d., and had been 

 previously subjected to 24,000 kgm. 



In view of this yield, therefore, the values at the higher pressures 

 which were evidently affected by this yield ha^ve not been included \\x 

 the figure. The curve connecting AF^ with the temperature has a 

 point of inflection, which is not shown by any of the other curves. 

 This is of significance, as will be seen. 



The values of A^ and t^E found in the ordinary way are shown in 

 Table XXVII. and Figure 34. The point of inflection in both these 

 curves is the particularly interesting feature. Water on passing to VI 

 gives out heat and absorbs work. The work is less than the heat, so 

 that the internal energy of VI is less than that of the liquid. 



The data obtained with the high-pressure apparatus may be used to 

 determine one other quantity which the other apparatus could not give, 



0° 10° 20° 30° 40° 

 TEMPERATURE 



-20 -10 



50° 60° 



Figure 34. The latent heat and the 

 change of internal energy when VI passes 

 to the Uquid. 



I 



