Erratic Phenomenon in Valleys. 225 



say, is the principal argument that has caused me to attri- 

 bute to the existence of glaciers which no longer remain, the 

 phenomena similar to those produced by the glaciers of the 

 present day, and which we meet with in so many localities 

 far distant from glaciers. The granitic and porphyritic rocks 

 of many valleys in Scotland exhibit polishings equally bril- 

 liant with those at present observed on the slaty serpen- 

 tines of the flanks of the glaciers of Monte Rosa. The 

 most remarkable of these polishings that I have seen in 

 Scotland are those of the banks of Loch Leven near Bal- 

 Jahulish, those of Glen Spean opposite Loch Treig, those 

 of Bunaw Ferry, those of Schiliallien, pointed out by Dr Buck- 

 land, and those of the neighbourhood of Edinburgh, where the 

 late Sir James Hall was the first to observe them. In Eng- 

 land, I have seen very fine instances between Shap and Ken- 

 dal, and near Ambleside ; and in Ireland, near Donaghadee 

 and near Virginia. I shall not here enumerate the numerous 

 localities where the polishing of the rock has disappeared en- 

 tirely or in part, but where the form of the surface still attests 

 its former existence, but will limit myself to the notice of a 

 very curious fact of this kind which occurs on the left bank 

 of Loch Treig. We have there a small hill of gneiss, of a 

 rounded form, whose surface is no longer fiat, but is traversed 

 by veins of quartz, having perfectly smooth and striated sur- 

 faces. The contours of these veins are exactly conformable 

 to those of the eminence ; they are cut according to the same 

 forms, but they are raised two or three inches above the sur- 

 rounding rock. Precisely the same phenomenon is to be seen 

 near the Hospice of the Grimsel, where veins of quartz, hav- 

 ing a polished surface, traverse roches moutonnees of gneiss, 

 whose surface has been rendered rough by the action of the 

 atmosphere. The projection of two or three inches of the 

 veins of quartz on the hill on the banks of Loch Treig, evi- 

 dently indicates the amount by which the neighbouring sur 

 face has been lowered by the decomposition of the gneiss, since 

 the time when the quartz was polished, and the whole emi- 

 nence rounded. 



Limestone rocks are equally polished in a multitude of lo- 

 calities ; but the most remarkable instances are in Lancashire, 



