526 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



are so chosen that heat is absorbed when the reaction runs in the direc- 

 tion in which the symbols read. Thus, the heat 1-L is given as 79.8. 

 This means that heat is absorbed when I passes to water. 



The changes of internal energy at the triple points are also given in 

 Table XXIX. The positive sign means that the reaction runs in the 

 direction indicated with increase of internal energy. 



TABLE XXIX. 

 Latent Heat and Internal Energy at the Triple Points. 



Point. 



III-L-I 



II-III-I 



V-III-L 



V-II-III 



VI-V-L 



A// gm. cal./gni- (in the first lines). 

 AE gm. cal. /gm. (in the second lines) . 



III-L 



II-III 



V-III 



V-II 



VI-V 



50.9 

 48.6 



12.3 

 1L2 



0.9 



- 3.6 



-16.0 

 -19.3 



0.2 



- 5.6 



L-I 



III-I 



III-L 



II-III 



V-L 



-56.1 



-62.8 



- 2.2 

 -12.2 



61.4 

 59.5 



16.9 

 15.7 



70.1 



62.4 



III-I 



II-I 



V-L 



V-III 



VI-L 



- 5.2 



-14.2 



10.1 

 ■ 1.0 



62.3 

 55.9 



0.9 



- 3.6 



70.3 

 56.8 



There are several considerations of interest in connection with the 

 diagram that are not directly concerned with the data as given. These 

 are the questions as to our knowledge that these forms are actually 

 solid, as to the possibility of other forms of ice, the possibility of exist- 

 ence of any form out of its region of stability, and the question of re- 

 action velocity. 



Are the Various Forms Really Solid? 



This is the first question that naturally presents itself as to this 

 work. The experimental evidence so far has merely been that there is 

 a discontinuous change of volume ; the new modifications have not 

 been seen ; it is impossible to take the pressure off and examine them, 

 because they are unstable ; why then are we justified in assuming that 

 they are solids and not liquids 1 No direct evidence on this point has 

 been collected in this work ; the improbability of their being anything 

 except solids seems so great as to make needless the special arrange- 

 ment of apparatus necessary to give a direct proof. This was doubly 



