any Evidences of former Glaciers in North Wales? 471 



There are, however, various appearances scattered here and 

 there through the districts I have named, which, if they have 

 not originated in glaciers, bear a sufficient resemblance to re- 

 quire a close examination. It is more important to make this 

 examination than may at first sight appear, in order to guard 

 those who have not witnessed the actual effects of glacial ac- 

 tion from attributing every accumulation of gravel or streaked 

 rock to such an origin. Though satisfied myself, from per- 

 sonal observation, that existing glaciers form moraines on their 

 sides and at their feet, and abrade the rocks over which they 

 move, so as to scratch and polish their surfaces, it has con- 

 stantly been my practice to see, in the first place, if the ana- 

 logous appearances I have met with in North Wales were not 

 capable, on taking into account all the local circumstances, of 

 satisfactory explanation by some obvious existing cause ; con- 

 ceiving it to be improper hastily to refer to the operation of ice, 

 effects which would admit of an equally easy explanation from 

 the transporting or erosive power of water. 



Of true lateral moraines ranging along the slopes of the 

 valleys more or less horizontally, and formed either of stones 

 or gravel, no instance has fallen under my observation. I 

 passed through many valleys, where, from the gradual rise of 

 the sides and the laminar or schistose structure of the rock, 

 the detritus from above had lodged and accumulated into a 

 talus, or formed continuous inclined planes of great uniform- 

 ity, which were often covered with herbage. This was stri- 

 kingly seen in the valley above Penmachno, but I could not 

 discover any trace of lateral moraines, nor of terminal ones, 

 about the outlet of the valley into the great trough of the Con- 

 way. In the neighbouring valley of the infant Conway, be- 

 tween Yspytty and Pentre Voelas, where the river first runs 

 parallel with the great Holyhead road, the slopes are covered 

 on both sides by a succession of rounded wavy knolls or swell- 

 ings, which are very striking in such a barren and rugged dis- 

 trict, from their smoothness and rich verdure, a character by 

 which they may be recognised at a considerable distance. 

 Near the lower end of the valley, on the east side, several of 

 them are detached, and are about fifty yards diameter and 

 twenty or thirty yards high ; but they usually run into one 

 another and are of no regular shape, except that they all slope 

 towards the stream, so that they look like great undulating and 

 projecting breastworks and bastions thrown up for military 

 defence. Some of these mounds cover an area of 100 acres, 

 and are two or three hundred feet high, looking like little 

 hills, but without any regularity or uniformity in the group- 

 ing,their bases running into one another and sloping towards 



