408 OBSEEVATIONS ON THE CUERENT3. 



could not then be explained. Again, by what power, or source of action, 

 are the lower strata made to move in an opposite direction to those super- 

 Incumbent upon them, and which, it might be supposed, would be acted 

 on by the same laws and move in the same manner ? 



The accuracy with which deep-sea sounding is now carried on haa 

 afforded a clue to this mystery. There seems to be a slow movement of 

 the cold waters on the bed of the Ocean from the Arctic and Antarctic 

 regions towards the Equator, forming one of the most remarkable evidences 

 of that grand compensating system by which the Great Creator has ordained 

 that all the harmonies of the universe shall be maintained — which keeps 

 the atmosphere and ocean in a perpetual condition of interchange, and thu3 

 makes them fit for the sustenance of his creatures. 



We have alluded to this universal intermingling of the ocean waters 

 before (246). Of the presence of Polar water in these Tropical regions there 

 can be no doubt. The following extracts from one of the earlier Eeports 

 of the United States Coast Survey* will place it beyond question : — 



" The Southern sections present, on a small scale, the same phenomena 

 which we formerly traced over a large expanse in the more Northern ones. 

 Examining the Canaveral section, which is the farthest South, we see the 

 Cold Wall almost as plainly as on that from Sandy Hook ; the curve, 

 showing the mean results between 70 and 100 fathoms, rises some 17° from 

 57^" to 74^° F., in the distance of 23 nautical miles. The warm water, 

 overlying the cold, is deeper in its overflow towards the shore — that is all. 

 Passing the warmest water, there is a fall of temperature of several degrees, 

 followed by a rise. On the St. Simon's section, the Cold Wall is again 

 well shown, and is the first of those distinct bands of minimum temperature 

 dividing four maxima, of which the greatest body of warm water of the 

 <3rulf Stream is the second from the shore. Near the surface the first ^nd 

 /ourth maxima are the highest ; at 15 fathoms, the first and second ; at 

 150 fathoms, the successive maxima rise as they recede from the shore. 

 The Charleston section presents, as a general feature, between 25 fathoms 

 and 250 fathoms, four minima and three maxima. Within the Cold Wall 

 minimum is a decided warm belt, and probably farther on inshore is a cold 

 one. The rise in the mean of the temperature, at 20 and 30 fathoms, is 

 11° F., namely from 64° to 75°. The advantage of not relying on surface 

 temperatures, or those near the surface, where the distribution is so much 

 less regular and marked than below, will be recognized in all these results, 

 and was early provided for in my instructions. 



" The underlying cold water from the Northern regions is as plain in the 

 Southern section as it was in the more Northern. At 400 fathoms ver- 

 tically below the warmest water of the Gulf Stream, on the Cape Henlopen 

 section, in August, 1846, the temperature was 49° F., and in the same 

 position off Cape Caiiaveral, in June, 1853, it was 48^°.t The latitude 



^ - ^ .. ■ ■ I ■ ■—■ - ■ ■ - — — .—-I- ■ ^ 



• Professor A. D. Bache, United States Coast Survey Report, 1853, pp. 48 — 49. 



t Reference may be again made to the note on the previous page relating to thesa 

 deep sea temperatures. The comparisons with more recent observations show that 

 these temperatures are too high by 2° or 3° at 500 fathoms, and perhaps as much aa 

 6' or 10° at 2,000 fathoms. This is owing to the great pressure of the water on th« 

 unprotected bulb of the thermometer forcing up the mercury. 



