298 BECKER AND DAY 



nature of viscosity and after action? Maxwell's theory of vis- 

 cosity ^ presupposes that various molecular groups are in dif- 

 ferent states, so that even a very rigid mass like steel contains 

 a certain proportion of fluid molecular groups. With so hetero- 

 geneous a mass as steel, this hypothesis ma}^ possibly be valid, 

 and yet it does not appear thinkable that in a single clear 

 crystal of a simple compound such as quartz or mica, a portion 

 of the molecular groups is in reality fluid, as Maxwell sup- 

 poses, and the remainder solid. It is very well known that a 

 high temperature (about 1800°) must be employed to convert 

 quartz into a glass, or in other words, to fuse it; that well 

 developed quartz crystals deposited from aqueous solutions at 

 temperatures below the boiling point of water could really be in 

 part fluid appears to us extremely improbable. On the other 

 hand, when crystalline masses possess a confused orientation, 

 as in the case of marble or of pure platinum consolidated from 

 a melt, it is at least thinkable that the difference of orientation 

 alone is sufficient to bring about the deformation of some mole- 

 cules before others have reached their elastic limit and the dis- 

 location of other molecules so oriented as to be ill supported by 

 their neighbors. It is possible that in this way the phenomena 

 of solid viscosity and after action may arise. 



It may be worth while to call attention to the fact that Kel- 

 vin's fourteen-sided solid suggests the possibility, and perhaps 

 the convenience, of a new resolution of the forces acting upon a 

 cube. The ordinary method of procedure is, of course, to 

 resolve a system of inclined forces acting on a cube into 6 

 normal and 12 horizontal components. Now if these 12 com- 

 ponents are combined three b}'' three, they may be replaced by 

 forces acting perpendicularly to the centers of the octahedral 

 faces ; and the phenomena seem to indicate that this is the 

 actual resolution in nature. 



^Maxwell supposes a solid to consist of i,'roiips of molecules of 2 kinds. Of 

 these, one kind shows relatively great stability and in a true solid is so abundant 

 as to build up a resistant framework. The other kind of group is so unstable as 

 to break up spontaneously or on slight provocation, and if it was exclusively 

 present the medium would be a viscous fluid. Maxwell ascribes the phenomena 

 of clastiche nach-virkuug' ox Kelvin's viscosity of solids, to a mingling of the 

 two sorts of molecular groups. (Constitution of Bodies in Encyclopedia 

 Brittanica. ) 



