ANTARCTIC CRUISE. 353 



and would pursue the direction it gives them. They would therefore 

 be driven to the northeast as far as the southwest winds prevail, 

 and when these veer to the westward would receive an easterly 

 direction ; it is where these winds prevail that they are most fre- 

 quently found by the outward-bound vessels, — between the latitudes 

 of 40° and 50° S. 



Respecting the period of time required for the formation of these 

 ice-islands, much light cannot be expected to be thrown on the 

 subject; but the few facts derived from observations lead to some 

 conclusions. Many of them were measured, and their altitude found 

 to be from fifty to two hundred and fifty feet ; eighty distinct stratifi- 

 cations were counted in some of the highest, and in the smallest thirty, 

 which appeared to average a little more than two feet in thickness. 

 Supposing the average fall of snow in these high latitudes to be an 

 inch a day, or thirty feet a year, the largest icebergs would take 

 more than thirty years to form. They were seen by us in all the 

 stages of their growth, and all bore unequivocal marks of the same 

 origin. The distance from the land at which they were forming, 

 fully satisfied me that their fresh water could only be derived from 

 the snows, &c. 



The movement of the ice along the coast is entirely to the west- 

 ward, and all the large range of ice-islands and bergs were found in 

 that direction, while the eastern portion was comparatively free from 

 it. A difference was found in the position of the floe-ice by the 

 different vessels, caused rather by the wind than by the tide. When 

 the Vincennes and Porpoise passed the opening by which the Pea- 

 cock entered, it was found closed, although only twenty-four hours 

 had elapsed. It has been seen that the ice had much movement 

 during the time the Peacock was beset by it, and the bay was all but 

 closed when she effected her escape. Another instance occurred, 

 where the Porpoise, in about the longitude of 130° E., found the im- 

 practicable barrier a few miles further south than the Vincennes did 

 six or seven days after ; but this fact is not to be received as warrant- 

 ing any general conclusion, on account of the occurrence of southeast 

 gales during the intermediate time. The trials for currents have, for 

 the most part, shown none to exist. The Porpoise, it is true, expe- 

 rienced some, but these were generally after a gale. If currents do 

 exist, their tendency is westward, which I think the drift of the ice 

 would clearly prove. The difference between the astronomic positions 



vol. 11. 89 



