222 On the Alpine Glacier, Iceberg, [No. 159. 



Mr. Darwin's researches in the opposite hemisphere show, that 

 the boulder formation, with all its European features, exists over ex- 

 tensive regions of South America ; in the plains traversed by the Rio 

 Santa Cruz (Lat. 50° S.) ; Tierra del Fuego,— -including the Straits 

 of Magellan and the Island of Chiloe (Lat. 43° S., Long. 73° W.) 

 Mr. Darwin, in order to account for the interstratification of regular 

 beds, the occasional appearance of stratification in the mass itself, 

 the juxta-position of rounded and angular fragments of various sizes and 

 kinds of rock derived from distant mountains, and the frequent 

 capping of gravel, follows Mr. Lyell in believing that floating ice 

 charged with foreign matter has been the chief agent in its formation ; 

 but, he adds, it is difficult to understand how the first sediment was 

 arranged in horizontal laminae; and coarse shingle in beds; while 

 stratification is totally, and often suddenly, wanting in the closely 

 neighbouring till, if it be supposed that the materials were mere- 

 ly dropped from melting drift ice ; and he is disposed to think that 

 the absence of stratification, as well as the curious contortions de- 

 scribed in some of the stratified masses, are mainly due to the dis- 

 turbing action of the icebergs when grounded. 



He believes also, that the total absence of organic remains in 

 these deposits may be accounted for by the ploughing up of the 

 bottom by stranded icebergs, and the impossibility of any animal 

 existing on a soft bed of mud or stones under such circumstances. In 

 conformation of the disturbing action of icebergs, Mr. Darwin refers 

 to Wrangel's remarks on their effects off the coast of Siberia 



Professor Hitchcock, and more recently Mr. Lyell, have made us 

 acquainted with the great extent of the boulder formation in North 

 America accompanied by parallel stria?, and rounded and polished sur- 

 faces of the harder rocks in situ ; also vast longitudinal mounds 

 and detached tumuli of detritus. The prevailing direction of the 

 strise observed by the former, as before observed, assimilated to that of 

 the furrows on the Scandinavian rocks, viz., from N. W. to S. E. 



The advocates of the iceberg theory consider these ridges and 

 mounds of unstratified gravel (the moraines of the glacialist) to have been 

 the wreck of icebergs freighted with the detritus of circumpolar rocks, 

 and stranded on the shores of seas, estuaries, or lakes ; or as having 

 been deposited in deep water by floating icebergs melting as they 

 approached warmer seas. The interstratified deposit, and occasional 



