8i 



that in all glacial districts, porous rocks beneath boulder clay or over 

 which ice has passed are contorted, torn and trailed, and but seldom 

 striated or polished. — 44. 



Striae can be seen on chalk pebbles in Lincolnshire, partly 

 because the chalk there is very hard, and chiefly because they have 

 been preserved in boulder clay. A good specimen from a brickfield 

 near Kingthorpe is shown. 



Mr. Jerome Harrison considers that the Yorkshire chalk wolds 

 were devoid of native glaciers, because the hill tops are covered 

 with loose weather-worn blocks which are neither smoothed nor 

 striated • and he attributes the absence of glaciers to a deficiency in 

 the snowfall. — 45- 



This appears to be a circular argument. There were no glaciers 

 because there was no snowfall ; there was no snowfall because there 

 were no glaciers. 



Moreover, it has been observed by Mr. Wright that in Southern 

 Greenland and in Labrador, the amount of glacial drift still re- 

 maining on land now free from ice is remarkably small. There is 

 scarcely any " till " in either region. The explanation doubtless is, 

 he thinks, that the loose material was nearly all removed and 

 deposited in the sea. — 46. 



And Mr. Mortimer has recently pointed out that though the 

 un-water-worn chalk gravel on the Yorkshire chalk hills was formerly 

 considered to be only rain-wash or rubbish disengaged by frost and 

 by ordinary atmospheric action, yet this gravel is not accumulated at 

 the base of slopes ; it is collected at elevated points and often marks 

 the scarps of eminences. It is the result of glacial agency. — 47. 



Coombes are not forming now. In fact many of them are filling 

 up. On this subject Mr. Clement Reid observes that at Fisherton, 

 near Salisbury, in beds which correspond with the coombe rock, 

 the remains of many species of high-northern mammals are found ; 

 and at Bovey Tracey, Devon (about 15 miles from the sea) in 

 similar beds, occur the Arctic birch, bearberry and Northern 

 willow. This, he adds, would indicate a mean temperature in the 

 South of England very considerably below the freezing point, so 

 that all rocks not protected by snow would be permanently frozen to 

 a depth of several hundred feet. He concludes that there was probably 

 little snow in the winter, and that there fell in summer torrential 

 rains which formed the coombes as the water ran off, unable to 

 penetrate the surface. — 48. 



On the other hand, Canon Gover, who had long studied this 

 question in the field, thought that the coombes had been excavated 

 by glacial ice. — 49. 



44— Glac. Mag., v., 137. 



45— Glac. Mag., iii., 74-5. 

 46 — Glac. Mag., ii., 142. 



47 — P.G.A., viii., 287. 

 48— Q.J.G.S., xliii., 369, 370-1. 

 49 — Ibid. 



F 



