ANTARCTIC CRUISE. 333 



their primitive form, were much worn, and showed many more signs 

 of decay. Near the extreme point of the barrier visited, in longitude 

 97° E., latitude 62° 30' S., and where it begins to trend to the west- 

 ward, vast collections of these islands were encountered. From this 

 point they must pass to the northward during the next season, partly 

 influenced by the current, and partly scattered by the prevailing winds, 

 until they reach the sixtieth degree of latitude, when they encounter 

 the easterly and north-easterly streams that are known to prevail, 

 which carry them rapidly to the north. 



Our data for their actual drift, though not altogether positive, are 

 probably the best that can be had, and will go far towards ascertain- 

 ing the velocity of their progress to lower latitudes; our observations 

 also furnish some estimate of the time in which they are formed. On 

 our way south, we did not fall in with ice-islands until we reached 

 latitude 61° S. The Peacock was the first to return, and nearly upon 

 the track by which we had gone south ; the last seen by her was in 

 55° S. The Vincennes, on her return fifty days later, saw them in 

 51° S. The Porpoise, about the same time, in 53° S. The observa- 

 tion in the Vincennes gives a distance of ten degrees of latitude, or 

 six hundred miles to be passed over in fifty days, which would give 

 about half a mile an hour; or, taking the Peacock's observations, a 

 more rapid rate would be given, nearly three-fourths of a mile. Many 

 icebergs were met in the latitude of 42° S., by outward-bound ships to 

 Sydney, in the month of November ; these, I learned, were much worn, 

 and showed lofty pinnacles, exhibiting no appearance of having ever 

 been of a tabular form. These no doubt are such as were detached 

 during a former season, and being disengaged from the barrier, would 

 be naturally, early the next season, drifted by the easterly current as 

 well as the westerly wind, and would pursue the direction they give 

 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 frequently found by the outward-bound vessels, — be- 

 tween 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 stratifications 

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

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



