396 ' NATURAL HISTORY. 



Desert of Sahara, and in Europe, the Mark of Branden- 

 burg, are found immense masses of sand, supposed to 

 be the disintegrated portions of rocks carried there by 

 the transporting power o'f -water; and so great is its 

 power of moving heavy substances, that even at the pres- 

 ent time, in the low-lying plains of Brandenburg, East 

 Prussia, and Russia, very large blocks of granite, em- 

 bedded in ice, are found deposited there, transported in 

 this way far from the places of their origin or point of 

 departure. It is impossible that these masses of rock 

 could have been carried there or kept afloat in any other 

 way than on ice cakes, which, as the velocity of the cur- 

 rent lessened, on reaching the level ground, were depos- 

 ited there. Animals and plants, embedded in similar 

 icebergs, have been carried by the same transporting 

 power to portions of the earth most remote from their 

 original homes ; for instance, trees or branches of the 

 palm family, natives of the far East, have been met with 

 in the iceblocks of the German Alps, and animals of the 

 antediluvian genus of elephants have been found in the 

 ice-fields of Siberia; their fossil remains uninjured by 

 the friction or obstacles met with in removal. 



The Glaciers, those beds of ice occupying the high 

 valleys of lofty mountain chains, as well as the ice-fields 

 of Siberia, and the so-called polar ice, are but the remains 

 of the great ice period, which has had much agency in 

 producing the present form of the earth. Granite and 

 some other unstratified rocks which were considered to 

 have formed the foundation stone of the great geological 

 edifice, it is now admitted, do not all date from an anti- 

 quity so remote, but are in reality younger than the 

 stratified or primary rock formations. Of still more 

 recent date are the unstratified or igneous rock forma- 



