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 marle 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 hand 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 Tilt, but after a considerable search I did not find any in those neighbouring parts where the surfaces of the rock were whitened, 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 produced 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 much more spungy and loose than chalk,
Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/326
