94 Correspondence — S. G. Perceval. 



tte mountain burns. It must not be supposed that, when the stone 

 is resting on the slope beneath a cliff, the work of destruction is over. 

 I suspect that in many cases, could we watch it, we should find it 

 proceeded with increased rapidity. A cube of stone in a cliff will at 

 most only offer three or four faces to the corroding action of air and 

 water, to the destructive influences of heat and cold ; the same, when 

 detached, will offer five or even six. As every mason knows, there 

 are not a few building stones that must not be used for corners. I 

 do not of course question Mr. Fisher's remark, " If the talus grows, 

 the inevitable result must be that the vertical face vsdll become in 

 time a slope ; " but I am not sure that the talus does grow ; at any 

 rate, I do not think that we can readily lay down a general rule ; 

 each case will have to be judged separately ; the growth will depend 

 upon the nature of the rock, the magnitude of the streams, the climate 

 of the locality, and many other causes which will greatly complicate 

 the question. Taluses may jncrease in one age, diminish in another ; 

 or at the same time be growing in one country, while dwindling in 

 another. With regard to that particular cirque in Skye of which 

 I spoke, I believe that a few able-bodied men could clear out in a 

 short day's work all the debris that has accumulated since the 

 Glacial epoch. It must not be forgotten, in the case of many rocks, 

 the destruction of the talus will not be confined to the surface ; the 

 streams often more or less sink into it, and wherever the water 

 makes its way, there disintegration will proceed, I believe therefore, 

 as I have said, that a talus does not necessarily mark more than a 

 stage in Nature's quarrying operation, and that she may be, and 

 sometimes is, quite competent to remove all her ' spoil ' without the 

 intervention of a glacier. With regard to the mode of formation of 

 cirqiTCs, I can only say that I have never seen one where 'there have 

 not been many small convergent streams, and that I believe the two 

 will be found as inseparable as cause and effect usually are. A qua- 

 quaversal dip would, no doubt, be favourable to the production of a 

 cirque, but I have no reason to suspect its existence in most of those 

 cases which I described in my communication to the Geological 

 Society. T. G. Bonnet. 



ON THE LIMESTONE AT CANNINGTON PARK.i NEAR BRIDGWATER. 



Sir, — As some doubts have been entertained as to the date of the 

 Limestone occurring at Cannington Park, it may be worth mention- 

 ing that I have lately had an opportunity of examining the corals 

 that have been collected from that locality by the Earl of Cavan, by 

 Mr. J. D. Pring, of 22, Hampton Park, near Bristol, and by the late 

 Mr. William Baker, F.G.S., of Bridgwater ; the specimens collected 

 by the latter being now in the Taunton Museum, 



They consist of the following Carboniferous genera and species : — 



1, Lithostrotion Martini. 4. Clisiophyllum turhinatwm. 



2, Lithostrotion irregulare. 5. Clisiophyllum, sp. f 



3, Lithostrotion aranea. 6. Syringopora ramuiosa. 



^ See Proceedings of Somersetshire Arcbjeological and Nat, History Society. Vol. 

 for 1860, p. 129; 1852, p. 125; 1854, p. 1U5. 



