in reply to a Paper by Mr. E. W. Brayley, jun. 103 



to contain distinct grains of quartz and fragments of other 

 constituent parts of granite;" but he adds, '* in time the 

 accumulated gravel is blown away by the winds, although 

 in the deeper hollows it may often be found forming consider- 

 able accumulations." In the first place, I very much doubt 

 whether it be really a fact that gravel of this description is 

 always found in these excavations, and indeed Dr. MacCul- 

 Joch's own remark seems to imply that it is not; for why 

 does he observe that in time the accumulated gravel is blown 

 away, if it were always found there ? But let us suppose the 

 statement to be correct, and in many of them such gravel or 

 sand, it will readily be admitted, is found ; then, I observe, 

 these particles of gravel or sand may as readily be supposed 

 to have been swept into the basins by the wind, as blown out 

 of them, and to have found a lodgement there : nor will any 

 one think this circumstance extraordinary, who has any know- 

 ledge of the violence of the winds in this district. 



Dr. MacCulloch proceeds to observe, that " the circum- 

 stances which occasion the formation of rock-basins are the 

 presence of water, and the alternate action 'of air and water. 

 Jf a drop of water can make an effectual lodgement on a surface 

 of granite, a small cavity is sooner or later produced. This 

 insensibly enlarges as it becomes capable of holding more 

 water, and the sides, as they continue to waste, necessarily re- 

 tain an even and rounded concavity, on account of the uniform 

 texture of the granite." Now we have no doubt that a con- 

 tinued stream of water, especially if it flow with rapidity, will 

 wear itself a channel, arid create hollows in the hardest 

 rock; and the Rev. J. P. Jones, the distinguished Botanist of 

 Devonshire, in his account of one of his tours on Dartmoor, 

 mentions a remarkable fact of this kind very much to our pre- 

 sent purpose. He states, that in crossing the streams on the 

 Moor, he observed, not only many small cataracts, but basins 

 in the rocks on the borders of the currents ; and that these cu- 

 rious cavities, however, were never formed unless the rapidity 

 of the stream, meeting with some obstructions, formed an 

 eddy. Here then is the operation of natural causes fully ade- 

 quate to the effect produced. A body of water perpetually 

 whirling round with considerable velocity, and carrying with 

 it, no doubt, gravel and stones, has insensibly, through a long 

 succession of ages, scooped out these rock-basins: but that a 

 drop of water, having found a lodgement on the horizontal 

 surface of the hardest granite, should, by chemical operation, 

 make any serious impression there, and that hence by the 

 gradual accumulation of water rock-basins should be formed 



on 



