CHAP. VII. J 



DEEP-SEA TEMPERATURES. 



323 



The ffeneral 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 050 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 ~¥\g. 

 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- 



v 2 



