446 Probable injiuence of 



time of the freezing and formation of the berg. The com- 

 paratively small number of icebergs seen in lower latitudes, 

 favor the conjecture that this must be a common mode of 

 destruction. Without some such agency, our oceans would 

 be completely obstructed with floating ice. 



The fixed limits which appear to be thus assigned to the 

 transport of icebergs is an interesting fact, and peculiarly so 

 in connection with the aqueo-glacial theories of drift, if the 

 statement made by Humboldt, and repeated by Darwin, is 

 correct, that no angular fragments are found in the vast inter- 

 tropical plains of South America, and that, within the south- 

 ern and northern hemispheres, no fragments coming from 

 polar regions or mountain groups arrive within any consider- 

 able distance of the limit of the tropics. 



IV. The most important view in which icebergs are to be 

 regarded is with respect to their influence in the transportation 

 of bowlders and angular fragments of rock and earth. Most 

 geologists unite in supposing that icebergs were important 

 agents in lifting and distributing the enormous bowlders and 

 erratic blocks which are found in the drift, at a distance from 

 their parent rocks. I shall give all the positive and negative 

 evidence which I have been able to collect upon this point. 



Captain William Rowland, who was in the constant habit 

 of landing upon the icebergs in the northern seas, observes 

 that he has often seen bowlders and fragments of rock from 

 four to six feet in diameter, although not more than one in a 

 hundred would have any foreign matters on it. Captain 

 Sampson, of New Bedford, informed me that he once saw, 

 on the sloping side of a large iceberg, upon the Banks of 

 Newfoundland, a large quantity of earth. It appeared to be 

 about a foot in thickness ; near the water it had been washed 

 away by the waves. The space thus covered seemed to him 

 to be about fifty feet in width, and an eighth of a mile in 

 length. 



Captain Barnum, of Stonington, informed me that he saw, in 

 latitude 55° south five large islands, whose surface was black 



