352 ANTARCTIC CRUISE. 



would be the last to dissolve, and these boulders would therefore in 

 all probability be carried to the farthest extent of their range before 

 they were let loose or deposited. 



The ice-islands, on being detached from their original place of 

 formation by some violent storm, are conveyed to the westward by 

 the southeast winds which are prevalent here, and are found, the first 

 season after their separation, about seventy miles north of the barrier. 

 This was inferred from the observations of both the Vincennes and 

 Porpoise, the greatest number having been found about that distance 

 from the barrier. That these were recently detached is proven by 

 their stratified appearance ; while those at a greater distance had 

 lost 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 westward, vast collections of these islands were en- 

 countered. 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 lati- 

 tude, 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 ascer- 

 taining the velocity of their progress to lower latitudes ; our observa- 

 tions 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 observation 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 Novem- 

 ber; 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, 



