107 



geological phenomena, when the exertion of a comparatively 

 feeble power will afford sufficient explanation. We very com- 

 monly observe in coal works, when the workings happen to be 

 very extensive, the lower beds swelling upwards, and sometimes 

 the upper bulging downwards until they meet, without produ- 

 cing a single crack ; here we have contortions of solid rocks by 

 a slow action, without those awful subterranean disturbances 

 and igneous matter to soften rocks, w r hich some geologists are 

 so fond of contemplating. The mere elevation and contortion 

 of mountain masses can be produced by a slow force as well as 

 by other means ; and the examination of these upraised moun- 

 tains shows that the effects could not be produced by one great 

 and instantaneous action. Contortion requires that the rocks 

 should be in a yielding state, and that the particles be capable 

 of a certain movement among each other, so that in applying 

 force no absolute fracture would occur. Were we to attempt to 

 bend a bed of limestone by one instantaneous action, the proba- 

 bility would be that it w-ould immediately break ; but if we gra- 

 dually apply pressure, so slow as to afford time for the consti- 

 tuent particles to adapt themselves to the change, the bed may 

 be subjected to any degree of contortion without fractures while 

 in situ ; where it is always saturated with carbonic acid and the 

 usual natural solvents. The volcanic forces are insignificant 

 compared with the apparent feeble force of magnetism ; it is like 

 the effect of a blow T from a sledge on a sheet of ice on a pond, 

 compared with those effects w T hich would be produced by water 

 if confined and connected with a hydrostatic press ; the former 

 would exhibit a great break in one individual spot, but the latter 

 w r ould fracture and bend the ice throughout by a slow and in- 

 sensible action. The disturbances thus produced on the ice 

 w 7 ould be greater*than those observed in the crust of the earth, 

 when viewed in their relative proportions. 



When we consider that rocks have been liable to be contorted 

 from the time they were in a state of mud to their consolidated 

 state, we can easily conceive why they should present such bends 

 as we now find in them. The extent to which the particles of 

 various rocks, saturated with water as they always are in na- 

 ture, may be compelled to move among each other by great 

 pressure, has never been sufficiently considered. Indeed rocks 



