138 PROFESSOR EDWARD HULL^ M.A., LL.T)., F.U.S., F.G.S., ON 



though ou a small scale as compared Avith those of Noi-way. 

 In both cases they are true rock-basins ; that is to say, 

 they are deeper near the centre than at tlie outlet formed of 

 ■solid rock, due to the erosive action of some agent which is 

 neither the original river, nor the sea, and which can, 

 therefore only have been that of glacial ice, aided by sand, 

 stones, and boulders imbedded in its mass, and imder enormous 

 pressure, wearing doAvn the floor of the valley during a 

 long period of geological time. The arguments of the 

 late Professor Sir A. C. Ramsay,* supported and illustrated 

 as they have been by Professor James Geikie, can alone 

 account for the numerous examples of rock-basins, both in 

 Norway and Scotland. The latter author takes all the 

 suggested "explanations" seriatim, and discusses them in 

 detail, showing that neither the action of the sea which 

 planes the siu'face down to a level, or of rivers Avhicli *' cannot 

 run upwards," nor the local foldings or faulthigs of the 

 strata^ nor local subsidences which he truly pronounces 

 "incredible" in the cases of such basins as those of the innu- 

 merable lakes of Scotland, Cumberland, Wales, Scandinavia, 

 Finland, and Switzerland can account for the phenomena.! 

 On the other hand it is easy to show that both in 

 Scandinavia and Scotland glacial erosion has been most 

 effective in the central or upper portion of each rock basin 

 or inland fjord, Avhere the mass of the ice descending from 

 the interior valleys may be assumed to have reached its 

 greatest thickness and weight ; while farther out towards 

 the sea, owing to gradual melting, the thickness of the ice 

 had diminished, and with this the erosive eh'ects. Thus were 

 a glacier to continue to flow for a sufficient length of time, 

 this unequal pressure upon the underlying rock would 

 produce some effect ; there would be a great deal more 

 wear and tear where the ice had been thick than Avhere it 

 had been thin, and thus a rock-basin Avould eventually 

 be formed. 



* " On the Glacial origin of lakes," Quart. Journ. Geol. Soc, xviii, 

 p. 185. 



t The Great Ice Age, p. 294. I have been tempted thus to dwell upon 

 Eamsay's views and Geikie's dtsfence of them longer than I had intended, 

 as they have been subject to c-ontention on the part of some less com- 

 petent to form an opinion. 



