Rev. 0. Fisher — On Faulting, Jointing, and Cleavage. 275 



and the accompanying elevation, were produced, part of the thickened 

 portion will have been forced relatively upwards, and part down- 

 wards ; if the movement was not almost infinitely slow, the sub- 

 stratum, owing to its inertia and viscosity, would not allow of the 

 position of hydrostatic equilibrium being assumed at once. 



Hence, the cessation of the elevatory action will have left the 

 distui'bed tract in too elevated a position, in which it could not remain, 

 but must sink more or less slowly, according as the substratum 

 was more or less viscous ; until at last the position of hydrostatic 

 equilibrium will have been attained. It is of course impossible to 

 predicate in what position the strata, which are now seen after 

 many vicissitudes to occupy known positions, will have been 

 originally left, when newly elevated. But if we assume an initial 

 position, and the ratio of the densities of the crust and substratum, 

 we can roughly indicate by a diagram the subsequent settlement. 

 Let us take, for the ratio of the densities, that of granite to basalt, 

 or of 2'68 : 2-96. This is very nearly the same as of ice to water, so 

 that the behaviour of ice floating on water will closely illustrate the 

 hydrostatic position of the crust when in equilibrium. 



1 I i LLJ'Jiiil iJJJjJJlLLLLIiiJ-iiJliJ-IJ-i._'--'JiJi 'iJiJiiJi 



In the figure, A B C is supposed to be the mean initial outline 

 of the elevated portion which has been forced upwards, abc of that 

 which has been forced downwards. The broken line is the effective 

 level of the substratum. If ^ ^ C7 sinks to P Q B, abc will sink to 



