CH. XXXIX. BOUCHER BE PERTHES. 415 



And just as we see now that icebergs break off from the 

 Greenland glaciers, carrying with them stones and mud, and 

 dropping them at the bottom of the sea ; so in those times 

 icebergs floated over many of the valleys of Europe, which 

 were then submerged beneath the ocean. You may see in 

 the railway- cuttings of Wales and in the sea-cliffs in the 

 coast of Yorkshire and Norfolk huge masses of glacial drift, 

 as it is called, made of mud and stones confusedly mixed 

 together, which were dropped from icebergs travelling south- 

 wards from the ice-fields. 



This period of cold is called by geologists the * Glacial 

 Period ; ' and when you read works on geology you will see 

 that it explains in a wonderful manner many curious facts 

 in the later history of our earth, and the distribution of 

 plants and animals upon it For the present it is enough 

 for you to remember that Agassiz first pointed out the signs 

 of this cold period, and that this discovery was one of the 

 earliest rewards of a patient study of causes which are going 

 on now ; for it is from the ice-action in Switzerland and 

 Greenland in the present day, that we are able to understand 

 how these huge ice-fields carried down erratic blocks and 

 the mud of moraines during the Glacial Period. 



Geological Proofs that Man lived npon the Eartli in Ages 

 long gone by, with Animals wMch are now extinct, 1847. 

 — The second remarkable discovery which has been made 

 in geology in this century is that of the antiquity of man; or 

 the fact that man must have existed upon our earth long 

 before the very earliest times of history or tradition ; in an 

 age when an elephant and a hysena, of extinct species, 

 roamed about England and France, together with some 

 other strange animals which are not now to be found upon 

 the globe. 



