352 PROCEEDINGS: PHILOSOPHICAL SOCIETY 



cent of the investigated cases, however, the high temperature form at 

 the inversion temperature has a lower specific heat; that is, its specific 

 heat after being higher reverses and becomes lower again. 



So, also, excellent atomic theories have accounted for the fact that 

 of two forms the one of larger volume* has the larger specific heat, but 

 it turns out that in 70 per cent of the investigated cases it is the more 

 dense form which has the larger specific heat. Again, it is a general 

 rule that as bodies are compressed their power to resist further compres- 

 sion increases, but out of 27 cases of inversion 17 had the form of smaller 

 volume more compressible. Finally, the high temperature form, 

 being produced by an absorption of heat, that is, by doing work against 

 attractive forces, would be expected to have a larger volume. In 25 

 per cent of the known cases even this expectation is not realized. 



In order to explain this last surprising circumstance, Bridgman 

 (whose experimental work has furnished the above results) points out 

 that we must suppose atoms to have shapes other than spherical with 

 centers of attraction situated elsewhere than in the center, but he 

 points out that the nonspherical form means merely that the centers of 

 repulsion (which by determining the resistance of the atom to pene- 

 tration by other atoms determine what we think of as its boundary), 

 must be distributed in a way which is very far from spherical symmetry. 

 It is idle to assign definite patterns to these distributions of centers of 

 force, but the fact is clear that while with atoms in any given arrange- 

 ment a slight compression involves the doing of work against the re- 

 pulsive forces, the rearrangement of atoms involved in a change of 

 state may produce changes of volume to which the change in energy 

 bears no correspondence. There is merely a 3 to i probability that they 

 will correspond in sign. About one solid substance in three is estimated 

 to show changes in crystalline form. 



In some work done by the speaker it turned out that the quartz 

 inversion, which has been known to be preceded by an abnormally large 

 and progressive change in volume and various crystalline properties, 

 also manifests an absorption of heat which is quite out of relation to the 

 work done in expansion, unless we suppose that the compressibility is 

 extraordinarily modified. Hence all the phenomena of this change, 

 which is detectable over a range of 500 degrees or more, have the char- 

 acteristics of a change of state, except that we do not appear to have 

 two different forms in equilibrium at the same temperature, as we do 

 in most other cases. The promptness of these changes affords a re- 

 markable contrast to other changes of state between quartz and other 

 .forms of silica, which are unusually sluggish. 



Discussion: This paper was discussed by Messrs. Williamson, 

 SoSMAN, BicHOWSKY, and Humphreys. 



Mr. F. B. SiLSBEE then presented a paper on Some peculiarities of 

 electrical conduction in porcelain. This paper was illustrated by lan- 

 tern slides, and has been published in this Journal (9: 252). 



Discussion: Mr. L. J. Briggs asked if electrodes other than those of 

 molten solder had been used. Mr. White inquired concerning the ef- 



