CHAP. XIV. DRIFT AND BOULDERS IN IRELAND. 273 



the general direction in which the boulders have travelled is 

 everywhere from northwest to southeast, a course directly 

 at right angles to the prevailing trend of the present moun- 

 tain-ridges. 



Maps illustrating successive Revolutions in Physical Geo- 

 graphy during the Post-pliocene Period. 



The late Mr. Trimmer, before referred to, has endeavored 

 to assist our speculations as to the successive revolutions in 

 physical geography, through which the British Islands have 

 passed since the commencement of the glacial period, by 

 four "sketch maps," as he termed them, in the first of 

 which he gave an ideal restoration of the original Conti- 

 nental period, called by him the first elephantine period, or 

 that of the forest of Cromer, before described (p. 214). He 

 was not aware that the prevailing elephant of that era 

 (^E. meridionalis') was distinct from the mammoth. At this 

 ei'a he conceived Ireland and England to have been united 

 with each other and with Fi-ance, but much of the area re- 

 presented as land in the map, fig. 41, p. 279, was supposed to 

 be under water. His second map, of the great submei-gence 

 of the glacial period, was not essentially diiferent from our map, 

 fig. 39, p. 276, His third map expressed a period of partial 

 re-elevation, when Ireland was reunited to Scotland and the 

 north of England, but England still separated from France. 

 This restoration appears to me to rest on insufiicient data, 

 being constructed to suit the supposed area over which the 

 gigantic Irish deer, or Megaceros, migrated from east to west, 

 also to explain an assumed submergence of the district called 

 the Wealden, in the southeast of England, which had re- 

 mained land during the grand glacial submergence. 



The fourth map is a return to nearly the same continental 

 conditions as the first, — Ireland, England, and the Continent 



