DEEP-SEA TEMPERATURES. 



37 



brightest gems. A large number of tabular icebergs, with quantities of snow on their 

 level tops, were met. They amused themselves by firing a 9-pounder Armstrong at one, 

 which brought the ice down with a rattling crash, the face of the berg cracking, splitting, 

 and splashing down with a roar, making the water below white with foam and powdered 

 ice. These icebergs were all stratified, at more or less regular distances, with blue lines, 

 which before they capsized or canted from displacement of their centres of gravity, were 

 always horizontal. During a gale, the Challenger came into collision with a berg, and lost 

 her jibboom, "dolphin-striker," and other head-gear. An iceberg in a fog or gale of wind 

 is not a desirable obstruction to meet at sea. 



The observations made for deep-sea temperatures gave some remarkable results. Here, 

 among the icebergs, a band or stratum of water was found, at a depth of eighty to 200 



THE NATURALIST'S ROOM ON BOARD THE " CHALLENGER." 



fathoms, colder than the water either above or below it. Take one day as an example : on 

 the 19th of February the surface temperature of the sea-water was 32 ; at 100 fathoms 

 it was 29-2 ; while at 300 fathoms it had risen to 33. In the Atlantic, on the eastern 

 side about the tropics, the bottom temperature was found to be very uniform at 35 - 2 p , while 

 it might be broiling hot on the surface. Further south, on the west side of the Atlantic 

 below the equator, the bottom was found to be very nearly three degrees cooler. It is 

 believed that the cold current enters the Atlantic from the Antarctic, and does not rise to 

 within 1,700 fathoms of the surface. These, and many kindred points, belong more properly 

 to another section of this work, to be hereafter discussed. 



The Challenger had crossed, and sounded, and dredged the broad Atlantic from 

 Madeira to the West Indies finding their deepest water off the Virgin Islands; thence 

 to Halifax, Nova Scotia; recrossed it to the Azores, Canary, and Cape de Verde Islands; 

 recrossed it once more in a great zig-zag from the African coast, through the equatorial 

 regions to Bahia, Brazil; and thence, if the expression may be used, by a great angular 



