318 Br, Mac CuLLocu on the Geology of Glen Tilt, 



and generally the surface-water from above trickles down their 

 faces. In these parts, thus subjected to the action of water, the 

 limestone is dissolved and deposits here and there a white crust of 

 carbonat of lime resembling the usual deposits of calcareous 

 waters, so as to whiten in many places the surface of the rock. 

 One cascade of considerable height has thus left the marks of its 

 intricate course in the dark and broken rocks so perfectly, that 

 even in dry weather it appears to be always flowing, and only 

 a narrow inspection discovers it to be an imitation ; a painted 

 cascade formed by the hand of Nature. I have been the more 

 particular in describing this fact and its extent, for the purpose 

 of showing that the marie bed is not produced by a deposition 

 of calcareous earth from the water thus impregnated. Were this 

 the case it should be found under the whole extent of this range 

 of rocks, whereas it is limited to one spot and that one a point 

 where the water flowing from above is diverted from it on each 

 band by sinuosities in the scarped face. I do not assert that 

 there is absolutely no other deposition of a similar nature in any 

 other place throughout the great extent of the limestone range 

 of Glen Tilr, but after a considerable search I did not find any in 

 those neighbouring parts where the surfaces of the rock were 

 w^hitened, and the greater flow of water would have led me to 

 expect it, had it been a mere deposit from water. There is little 

 doubt that a portion of the lime contained in the bed has been pro- 

 duced in this way, but that portion must necessarily be small, or the 

 same earth would be easily discovered in the soil of the immediate 

 vicinity which lies in similar situations, which has nevertheless 

 only the ordinary aspect of the whole mass of soil incumbent on 

 the limestone. On examining the nature of this deposit it is found 

 to consist of a substance niuch more spunky and loose than chalk, 



