Mr Mnrchison on the Glacial Theon/. 129 



pointed out by Sir James Hall, and which the great chemical geologist 

 attributed to a powerful rush of waters. When I visited the low ridge in 

 question with Dr Buckland and other friends,* my conviction was tliat 

 these grooves, though then attributed by Dr Buckland to glacial action, 

 are due neither to tliat agency, nor to any rush of water.^, but are simply 

 the result of the changes which the mass of tht; rock underwent, when it 

 passed from its former molten or pasty condition into a solid state. These 

 appearances diflPer essentially from ordinary glacial scratches or scorings.t 

 They are, in fact, broad undulations or furrows, and instead of trending 

 from the higher grounds to the Firth of Forth, as would naturally be the 

 case if they were due to the expansion and descent of glaciers, they rise 

 up to the very summit of the low ridge in a direction transverse to its 

 bearing, and with no neighbouring point of ground higher than that on 

 which they occur. On clearing away the thin turf which barely covered 

 the rock, some of these undulations in the surface appeared wide enough 

 to contain the body of a man, and though observing a rude sort of paral- 

 lelism, their forms were often devious. As their surface was smooth, not 

 much unlike the usual aspect of the so-called " moutonnes" rocks, the 

 glacialists of our part}' at first seemed to be proving their case, when sud- 

 denly a discovery destroyed, at least in my opinion, their theory ; for in 

 the adjacent quarries of the same hill, at a much lower level, and upou 

 beds just uncovered hy the workmen from beneath much solid stone, other 

 sets of undulations or grooves were detected, so like to those upon the 

 summit of the hill, that a little atmospheric influence alone was required 

 to complete theit identity. My belief therefore is, that the undulations 

 were caused by the action which took place when the stone was solidified. 

 Phenomena of a similar nature to the Scottish have been since ob- 

 served in Wales by our late Fellow, Mr Bowman. Captivated by the 

 glacial theory, and having himself endeavoured to shew that it could 

 even be as successfully applied to the south as to the north of Scotland, 

 he examined the highest region of Wales, with the geological structure 

 of which he was previously familiar, half convinced, a priori, that he 

 would naturally find in those mountainous tracts some proof in support 

 of the new views which he had adopted. He, however, quitted that 

 country without having been able to observe any evidence whatever in 

 favour of the Alpine theory, though his journey enabled him to detect 

 several exami^les of striated rocks, which in unskilful hands might have 

 been mistaken for the effects of glacial action ; and these he holds up as 

 warning beacons. After stating that there are, in his opinion, no ter- 

 races which any follower of Agassiz can construe into "moraines," whe- 

 ther terminal, medial, or lateral, on the flanks of the mountains of Snow- 

 don, the Arenigs, or the Berwyns, he describes three distinct and diffe- 



* Dr Graham and Mr Maclaren were of the party, in October 1 840. 

 t Plaster casts of these exist in the Geolojflrftl S«xriety. 



VOL. XXXIir. NO. LXV. JULY 1842. I 



