= 
3 
Bibliography. 163 
that distance from the barrier. That these were recently detached is proved by 
their stratified appearance ; while those at a greater distance had lost their prim- 
itive 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 
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 northeasterly 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 ascertaining the velocity of their pro- 
gress 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 519 S. The Porpoise, 
about the same time, in 53° S. The observation in the Vincennes gives a dis- 
tance 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 ob- 
servations, 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—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 de- 
rived from observations Jead to some conclusions. Many of them were measured, 
and their altitude found to be from fifty to two hundred and fifty feet ; eighty dis- 
tinct 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. 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 be derived only from the snows, &c. 
«“ The movement of the ice along the coast is entirely to the westward, and all 
the large ranges 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 po- 
sition 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., 
