96 DISPOSITIONS, FRACTURES AND 



reaching the lowest bed; which is evidently the very 

 depth, be it what it may, that is actually exposed to 

 the light of day. It may be much more; and thus 

 we see within the earth as perfectly as if it were 

 transparent. It is unnecessary to name examples of 

 a fact which occurs in every part of the world; but it 

 has been computed by Mr. Playfair from an observa- 

 tion of Pallas, that in this one instance quoted from 

 him, we probably gain access to 61 miles in depth, 

 or nearly a sixty-fifth part of the radius of the 

 globe. 



It is however necessary to modify this general con- 

 elusion. The unterminable, or even distant prolon- 

 gation of inclined strata downwards, is no more pro- 

 bable than their uninterrupted continuity on the 

 surface. All rocks appear to be, in a certain sense, 

 partial and limited. They are, moreover, subject to 

 fractures and displacements, which must interfere 

 with such conclusions respecting their prolongations 

 beneath the surface. The very fact of elevation and 

 displacement implies this ; while we have, otherwise, 

 no reasons, a priori, for supposing that strata depo- 

 sited from an ocean, however antient, can exist 

 beyond a certain, however undefined, depth ; while 

 the repetitions of beds in contrary positions, assure 

 us that the depositions of such strata have been the 

 consequences of alternate destruction and renewal. 



An example or two will serve to illustrate the na- 

 ture of the limitations to be made in reasoning re- 

 specting the depths of strata beneath the surface. In 

 the Argyllshire series already described, it was shown 

 that the appearances were easily accounted for by a 

 theory which would prove their depth, either now or 

 in their original position, to be very limited. Nor is 

 there anv reason to imagine that thev extend to great 



