i 9 4 PREHISTORIC EUROPE. 



have long been known, but one of the most noted by reason of 

 its great size is that which is exposed in the clay-pit, called 

 Eoslyn Hole, near Ely. This erratic is composed of a mass of 

 Chalk, Gault, and Upper Greensand, and measures over 480 

 yards in length by 44 yards in width. The Eev. 0. Fisher 

 was the first to recognise its true character, Mr. Seeley having 

 previously accounted for its presence by a fault or dislocation. 2 

 But Professor Bonney has shown that Mr. Fisher's interpreta- 

 tion of the phenomena is correct 3 — a conclusion which is like- 

 wise supported by the testimony of Mr. Skertchly, who states 

 that he has seen boulder-clay underlying all the various rocks 

 of which this enormous erratic is composed. 4 Similar large 

 detached masses of marlstone are described by Mr. Judd as 

 appearing in the boulder-clay of Lincolnshire, 5 and Professor 

 Morris mentions the occurrence in the drift of the same county 

 of a large erratic of Oolitic rock measuring 430 feet long by 30 

 feet thick at its deepest part, which he saw exposed in the rail- 

 way cutting at the south end of the tunnel (Great Northern 

 Kail way). 6 



The lower part of the boulder-clay in Cretaceous districts is 

 frequently crammed with masses of chalk and chalk-e^&?"is, and 

 these are so often crushed and kneaded together that it is diffi- 

 cult sometimes to distinguish between the broken upper surface 

 of the undisturbed chalk and the highly chalky till that overlies 

 it. And not only so, but occasionally we find the till and the 

 chalk appearing to alternate in successive irregular layers, some 

 instructive examples of which were pointed out to me by Mr. 

 Skertchly in the neighbourhood of Brandon and Thetford in 

 Sussex. 



Nowhere in Europe are the old glacial phenomena developed 

 on so imposing a scale as in Scandinavia. If we except the 

 higher mountain -tops, the whole of the great peninsula has 

 been wrapped in ice, the erosive effects of which are seen in the 



i Geol. Mag., vol. v. p. 407. 2 Ibid. vol. ii. p. 529. 3 Ibid. vol. ix. p. 403. 



4 Geology of the Fenland (Mem. Geol. Surv. Engl, and Wales), p. 236. 



5 Explanatory Memoir of Geol. Survey's Map (England), Sheet 64. 



6 Quart. Journ. Geol. Soc. , vol. ix. p. 320. 



