DILUVIUM. DRIFT AND ERRATIC BLOCKS. 



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successive waves of translation, which invaded the existing dry land, destroyed its 

 organic life, and spread over it the various boulders and foreign debris that now appear 

 upon its surface. This hypothesis receives support from several considerations. It is 

 in harmony with the positive events of bygone ages, and of the present epoch, as in 

 the formation of new islands, and the tremendous wave that shattered the coast of 

 Portugal during the earthquake of Lisbon. It 'is mathematically demonstrable that 

 sudden vertical elevations, each not exceeding 58 feet in the case of an ocean of 300 

 or 400 feet in depth, would produce waves having the power of hurling on enormous 

 blocks, sand, and gravel to vast distances, and over considerable inequalities, while it 

 accounts for the southerly direction of the drift, and the frequent presence of sea-shells 

 in the same sepulchre with the remains of land quadrupeds. 4. Agassiz, struck with 

 the transporting force of glaciers, which advance by their own gravitation upon inclined 

 surfaces, and break off masses of rock from the sides of the valleys, bearing them away 

 to a distant locality in the course of years, has endeavoured to show that the drift 

 around the flanks of the Alps has been abstracted from the mountains, and carried thither 

 by ancient and more extensive glaciers, which once covered, in fact, the whole of 

 Switzerland. Starting from this point, he has attempted to establish a general glacial 

 theory, according to which a sudden reduction took place in the temperature of the 

 surface of the globe, at the close of the tertiary period, whereby all organic life was 

 destroyed, and the northern regions were converted into one vast mer de glace, which 

 sent out enormous glaciers in a southerly direction. These he conceives to have 

 smoothed, furrowed, and striated the rock-surfaces over which they passed, and to have 

 carried along with them masses of entangled blocks and detritus, which were distri- 

 buted far and wide, by the violent torrents occasioned through a raising of the tem- 

 perature melting the glaciers. The development alone of this theory is due to Agassiz, 

 for it was first suggested by M. Venetz, a Swiss engineer, and afterwards advocated by 

 M. Charpentier. The reader will anticipate the chief difficulty in its way, the marked 

 temporary alteration of the temperature, which could only have transpired through some 

 transient derangement in the planetary relations of our globe. These are the chief 

 theories proposed respecting the deposits under consideration, and probably a variety of 

 agencies, to which each hypothesis contributes, has operated in their production. 



Diluvial Formations seen from the Acropolis at Athens. 



