Page:The Depths of the Sea - Wyville - 1873.djvu/374

 CHAP. VII.] DEEP-SEA TEMPERATURES, 323 350 fatboms 9^ •5 a less than 300 fathoms. 0° -.3 0. 400 „ . I) ►17 350 „

•3 450 „ . 8 1 „ 400 „

•5 500 „ . 8- 55 450 „

• 15 550 „ . 8"

500 „

'55 GOO „ 7 • 4 „ 550 „

•5 650 „ G • '83 „ GOO „

•G 700 „ G • 44 „ G50 „ • 4 750 „ 5 • 83 700 „ • G 800 „ 5 • 55 750 „ • 3 8G2 (Bottom) 4 • 3 800 „ 1 • 25 The general result of these two series of soundings is very important. The high temperature reduced hy T'^ C. in the first series at 250 fathoms is undouhtedly due to superheating by direct solar radiation. This is shown still more clearlv in the second series, where nearly 4° C. are seen to be lost between the surface and 30 fathoms, and somewhat above 2° C. more between 30 and 100 fathoms. From 100 to 500 fathoms the temperature is still high and tolerably uniform, and it falls rapidly between 500 and 1,000 fathoms. A reference to the second series shows that this rapid fall is between (550 and 850 fathoms, in which inter- val there is a loss of more than 3° C. This second stage of elevated temperature from 250 to 700 fathoms, which is represented graphically by the singular *hump* on the temperature curves in Fig. 61 and Plate VI. would seem to be caused by the north-easterly reflux under peculiar conditions, which will be referred to in next chapter, of the great equatorial current. From 1,000 fathoms down- wards, the loss of temperature goes on uniformly at the rate of about 0°'3 C. for every 250 fathoms. The most singular feature in this decrease of tem- y2