149 



familiar with in stratified rocks. Sir Wyvil Thompson 

 describes the bergs seen by him as being of a beautiful blue 

 colour, gradually deepening in tint towards the base, and 

 states that all were of the tabular form, and that they did 

 not see one single berg whose appearance indicated that it 

 had been formed by passing down a valley or over uneven 

 ground, nor were any seen carrying rocks, stones, or gravel. 

 As Antarctic bergs are often met with upwards of 150 feet 

 high above the water line, and. as from their specific gravity 

 they must have at least eight times as much depth below 

 water, it follows that they have a total thickness of at least 

 1,400 feet. The bergs are met with as low as 42deg. S., and 

 the Hon. Audley Coote informs me that he has encountered 

 several in about that latitude within a few hundred miles of 

 the Tasmanian coast. Wilkes says that in the year 1832 

 bergs were so numerous about Capo Horn that vessels were 

 compelled to return to Valparaiso. The largest berg measured 

 was 210 feet above the water line. 



The pack ice of the Antarctic seems to be much more 

 broken than that of the Arctic. Ross says that they rarely 

 saw a piece more than a quarter of a mile in circumference, 

 whereas in the Arctic seas pieces four miles in diameter were 

 met with, and at times the pack consolidated into " fields," 

 covering the sea as far as could be seen from the ship. This 

 difference is ascribed to the fact that the Antarctic seas are 

 rougher than the Arctic. 



In the Arctic regions the large extent of the land masses, 

 a,nd the influence of warm currents produced by the dispersion 

 of the Gulf Stream exert an ameliorating influence upon the 

 climate teuding to break up the ice. In the south no such 

 influences exist, and therefore the summer climate is colder 

 than the northern climate in corresponding parallels. As to 

 the winter climate we can only form conjectures, as no one 

 has yet wintered within the Arctic circle. Maury, who had 

 ample opportunities of forming opinions as to the climates of 

 both regions, thinks that the mean temperature is higher in 

 the south than in the north, and there is some evidence to 

 support his theory. A self-registering thermometer was left 

 on the South Shetland in latitude 63deg., and after remaining 

 there for several years it was examined and found to register 

 a minimum of 37deg. E. below r freezing point ; the mean 

 winter temperature of several localities in the same latitude 

 north is 68deg. P. below freezing. It would appear that 

 various points in the outline of the ice are influenced by 

 warm currents, for although so much of the great equatorial 

 current as is deflected south is, to a great extent, swallowed 

 up in the vast expanse of ocean, yet some portions escape, 

 and their influence can be traced. 



