538 E. W. Hilgard on Mallets Theory of Vulcanicity. 
however great may be the guantity of work performed, or of heat 
roduced. And very many, if not the majority of extensive 
faults actually occurring, show evidence of having been formed 
without cataclysmal disturbance. 
Among the other points raised by Hutton (loc. cit.) there are 
several which are at once disposed of by a perusal of the orig- 
inal memoir. There are others of some weight. That ‘‘lines 
of least resistance once chosen must remain,” is doubtless true 
in a very wide sense; and in that sense this is scarcely at 
variance with observed facts, since the lines of weakness along 
down of the crust-fragments in consequence of interior contrac- 
tion. Hach 
space of two independent factors (viz: of a condition of very 
unstable equilibrium of some crust fragment, with a tid 
e), in order to produce a maximum of disturbance. It 
cannot be expected that such coincidence should be of frequent 
occurrence, or that the casual connection should manifest itself 
in a greater predominance than that claimed by Perrey for the 
