GLACIAL EPOCH. 1G5 



preceded by palapteryx and dinornis ; and' the still more 

 gigantic aepyornis of Madagascar foreshadows the advent of 

 the ostrich of Africa. 



In the elimination of these successive fauna long ages 

 must have passed away ; and during these ages vast physi- 

 cal changes were necessarily effected on the terraqueous 

 relations of the globe. In the northern hemisphere, some 

 of the principal mountain-chains the Alps, Apennines, 

 Carpathians, and Himalayas had been gradually assuming 

 their ultimate configuration ; and the large inland seas that 

 had occupied the central latitudes of Europe, of Northern 

 Africa, Middle India, and Eastern Siberia and China, had 

 been elevated successively into shoals, lake, and island, 

 swamp and dry land. Simultaneously with these terra- 

 queous changes, the genial temperature that ushered in the 

 eocene period of Europe and America began, stage by stage, 

 to decline ; the miocene was marked by more temperate 

 manifestations ; and ultimately the pliocene sank into a 

 condition incompatible with the existence of the former 

 flora and fauna. A cold, glacial, and barren period ensued, 

 and under its rigours pliocene life in the northern hemi- 

 sphere succumbed, and was succeeded by genera and species 

 akin to those that now people the boreal regions. 



This ungenial period, generally known in geology as the 

 "Glacial," "Northern Drift," or "Boulder Clay" epoch, is 

 lithologically characterised by its superficial mounds and 

 masses of drift-sand and gravel, by thick tenacious clays, 

 interspersed indiscriminately with water- worn blocks of all 

 sizes, from mere .pebbles to boulders many tons in weight, 

 and by the polished, rounded, and striated surfaces of the 

 subjacent rocks, as if they had been subjected to the long- 

 continued friction of water or ice-borne material, and 

 scratched and furrowed by the passage of the harder and 



