MACINTOSH ON SUPPOSED GLACIERS IN N. WALES. 465 



Welsh slates, is also suggested as the probable explanation of 

 similar appearances elsewhere. 



3. Polished Rocks. — The surface of rocks of various kinds and 

 at very different elevations, has frequently been observed to ex- 

 hibit a polish, which has usually been attributed of late to the 

 action of ice. The author considers that some of these cases are 

 doubtful ; that the polish is not of long endurance when the surface 

 is exposed ; and that in some, at least, of the examples in North 

 Wales, the polish has been produced by the sliding of boys on 

 the smooth rock. This latter explanation he considers as suf- 

 cient in the case mentioned by Dr. Buckland at Bedd-Gelert, 

 near Pont-aber-Glasslyn, where a portion of surface, measuring 

 about 15 feet by 2 feet, is obviously polished, but where the rock is 

 weathered, and does not exhibit the appearance except at this spot. 

 Another example at Bedd-Gelert, at the north-east of the village 

 near the turnpike, also quoted by Dr. Buckland, is considered by 

 the author insufficient to support the glacial theory ; since, although 

 in this case the rock is intersected by numerous quartz veins 

 which project about two inches above the surface, but preserve 

 their polished and rounded outline, other similar appearances, 

 which could not have been produced by ice, occur also in rounded 

 rocks, as, for instance, in narrow recesses having angular edges 

 which no glacier could have touched. The author considers that, 

 as such apparent polish is not seen in the great majority of cases ; 

 it may be due to varying mineral conditions * ; but he expresses 

 his conviction that, as the surface apparently polished has, in 

 every case that he examined, been manifestly a weathered surface, 

 it cannot possibly have been produced by glacial action, since the 

 actual surface would in that case be exhibited, and not the 

 weathered coating, which is necessarily of much newer date. At 

 any rate, whether, as he believes, the polishing of rocks is in no 

 case attributable to ice, in any shape, but always to some other 

 mechanical causes, or to atmospheric exposure ; or whatever the 

 cause may be, the polish cannot have been retained unaltered 

 during so long a period ; and even if it could, since this appear- 

 ance belongs, not to a freshly exposed surface, but to a surface 

 covered by a film of decomposed rock, it certainly was not that 

 over which the ice passed. 



4. Moraines. — The instances adduced by Dr. Buckland in North 

 Wales as referable to this class of glacial phenomena are consi- 

 dered by the author as unsatisfactory ; and he refers, first, to the 

 elevated plain of. Pentre-Voelas, said to present large accumula- 

 tions of unstratified detritus having the aspect of moraines, but 

 supposed to have been afterwards modified by the action of water. 

 It is objected, that in this detritus there are no true rounded and 

 striated blocks nor rounded pebbles, neither are there mixtures of 

 different fragments of all forms and sizes, such as usually belong 



* The author here observes, as an additional argument against the probability 

 of glaciers having formerly existed where this so-called polished rock appears, 

 that the rock abounds with concretions standing in relief above its general 

 surface. 



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