CHAP, vn.] DEEP-SEA TEMPERATURES. 323 



350 fathoms 9 3< 5 C. less than 300 fathoms . 0- 3 C. 



400 . 9 17 350 .0-3 



450 . 8 7 400 .0-5 



500 . 8 55 450 .0-15 



550 . 8-0 500 .0-55 



600 . 7-4 550 .0-5 



650 . 6 83 600 .0-6 



700 6 44 650 .0-4 



750 5 83 700 .0-6 



800 5 55 750 .0-3 



862 (Bottom) 4 3 800 .1-25 



The general result of these two series of soundings 

 is very important. The high temperature reduced by 

 7*5 C. in the first series at 250 fathoms is undoubtedly 

 due to superheating by direct solar radiation. This 

 is shown still more clearly 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 650 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 YI. 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 tern- 





