101 Mr. Moore's Remarks on the Origin of Rock-basins ; 



on these flat surfaces, some of which, as Dr. MacCulloch ob- 

 serves, " are as regularly spheroidal internally as if they had 

 been shaped by a turning lathe, " and it may be added some 

 of which also are several feet in diameter*, to the reception 

 of this proposition my power of credence, I confess, is not 

 equal. I see here, indeed, a theory supported by a distin- 

 guished name, but by no sufficient proof. Mr. Brayley him- 

 self states a fact in direct hostility to this hypothesis. There 

 are granite beds, it seems, which present basins on their per- 

 pendicular faces ("Devon," p. 292 294-); and water might 

 indeed be arrested there by a miracle, but if.it followed the 

 course which nature requires, it would certainly descend, and 

 leave the rock as before. Some other cause therefore must 

 necessarily be sought for, to account for the production of these 

 basins at least. 



But if we are to suppose that rock-basins can be formed 

 by "the presence of water, and the alternate action of air and 

 water," and if, as Mr. Brayley affirms, " we need not hesitate 

 in admitting the solution of granite in water to an extent ca- 

 pable of producing this effect of disintegration," then I ask, in 

 what state ought we to find the granite in the beds, or rather 

 at the sides of the rivers near the surface of the water, where 

 it must be constantly exposed to the alternate and powerful 

 action of air and water? Worn indeed it may be by the 

 current, together with the sand and stones which the water 

 carries along with it; but that it is corroded chemically, and 

 that to a great degree, in conformity with Dr. MacCulloch's 

 theory, by the operation of both these elements, does not ap- 

 pear to be the fact j-. 



Again : if cavities can be formed in the rock in the manner 

 Dr. MacCulloch supposes, then I maintain, the whole of 

 the horizontal surface of the rocks would be corroded, and 

 would be generally as full of hollows as a honeycomb, though 

 with nothing of the regularity of the latter, for a drop of water 

 would easily find a lodgement in numerous places. This 

 however is not the case on any of the rocks in Devonshire ; on 



* Borlase states the diameter of some of them to be six feet. 



f A valuable correspondent of Plymouth, who has much informa- 

 tion on these subjects, after expressing his concurrence with the brief 

 remarks in defence of the artificial origin of rock-basins which gave occa- 

 sion to Mr. Brayley's discussion of the subject, observes, " There may be 

 instances in which Dr. MacCulloch's theory is verified, but I have never 

 found moorstone decomposing under the drip of water; and why are the 

 rock-basins so often upon the highest ridge of these stones, if they be not 

 artificial ?" 



the 



