289 EDITORIAL 
These contributions and the following one also strengthen the 
view that transitions of form take place by fractional action, 
portions passing to the fluid state and back again in succession 
while the larger portion at any one instant remains solid. It is 
of course well known that some geologists regard the deformations 
and movements of ice and of other crystalline rocks as a process 
of this kind, though more commonly assigned to viscous or plastic 
properties. 
In the interest of sharper analytical discriminations, Johnson 
and Adams’ have drawn clear lines of distinction between different 
kinds of pressure and their diverse effects. Their welcome paper 
clarifies a field over which fog has hung rather thickly. This 
clear demarkation of distinctions will no doubt help relieve ‘‘plas- 
ticity’? of an overburden of service as the putative creature of 
hydrostatic pressure. It will then be free to come into proper 
service occasionally as unbalanced stress invokes it. Let us hope 
that the notion that free and easy movement goes with “‘pressure 
plasticity’? may be honored with a place on the historic shelf, and 
that a place beside it may be reserved for its close cousin, the 
notion that “‘flow’’ of rocks under differential pressure carries 
the quality of facile fluency. 
It is prudent to note, however, that new light is often only 
partial light, sometimes merely a dim dawning that may lead 
astray rather than make clear the true way. Some of the deter- 
minations of Tammann,? important as they are in themselves, 
were so interpreted at first as to seem to some geologists to lead 
back to the old view of fluidity wherever in the heart of the earth 
pressure is great, but the still more extended experiments of Bridg- 
man with their acutely critical interpretations point to solidity 
and rigidity,’ as do so many other lines of recent inquiry. 
Most of these other lines are familiar, but the full significance 
of the determination of the body tide of the earth by Hecker’ 
t John Johnson and L. H. Adams, “On the Effect of High Pressures on the Physi- 
cal and Chemical Behavior of Solids,’ Am. Jour. Sci., XXXV, March, 19173. 
2 Kristallisieren und Schmelzen, Barth, Leipzig, 1903. 
5 Op. cit., PP. 430, 437; 553-57- 
40. Hecker, ‘‘Beobachtungen an Horizontalpendelen,” etc., Veréff. d. Kénigl. 
preuss. geodat. Inst., 1907. 
