544 



Dr. W. B. Carpenter on the 



[June 13, 





oiuu oea. 



China oea. 



Surface 







83 



o 



84 



30 fathoms 





77 



40 „ 





74 



50 to 80 fathoms 





71 





64-5 





120 „ 





G2 



150 , . 





56 



200 „ 



56-2 



51 







A 



308 „ 



51-5 





416 „ 





41 



500 to 1778 fathoms 



50 









37 



Thus it appears that with surface-temperatures almost exactly identical, 

 and with a rate of descent through the first 100 fathoms which seems 

 nearly the same, there is a most marked difference beneath. For whilst 

 in the Sulu Sea the thermometer only falls to 56°*2 at 200 fathoms, to 

 51 j° at 308 fathoms, and to 50° at 500 fathoms, and the temperature is 

 uniform from that point down to the bottom at 1778 fathoms, it descends 

 rapidly in the China Sea to 5 1° at 200 fathoms, thence to 4 1° at 4 1 6 fathoms, 

 and thence to 37° at 550 fathoms, at which point it remains stationary down 

 to the bottom at 1546 fathoms. This difference is attributed by Capt. 

 Chimmo — in my opinion with adequate reason — to the exclusion from the 

 Sulu Sea of the deep Polar flow which lowers the temperature of the 

 China Sea. That the uniform temperature of its deep water from 500 

 fathoms downwards is lower by 4° or 5° than that of the Mediterranean, 

 notwithstanding that the temperature of its superficial stratum is consider- 

 ably higher, can be easily accounted for on the very probable supposition, 

 that there are passages between the reefs and islands which admit 

 water of a temperature below 50° from the outside Sea ; in fact we might 

 almost certainly fix the minimum depth of such passages as about 250 

 fathoms. (See also the Addenda in pp. 589, 590). These contrasts — 

 graphically represented in Plate III. (in which the dotted lines show the 

 temperatures of the inland Seas, and the continuous lines the temperatures 

 of the adjacent Oceans) — are readily explicable on the doctrine of an under- 

 flow of Polar water towards the Equator ; and how they are otherwise to be 

 accounted for, I am myself at a loss to conceive. 



13. This underflow involves, as its necessary complement, a movement 

 of the upper stratum, bearing with it the warmth of Temperate seas, to- 

 wards the Pole ; and of such a movement very cogent evidence is afforded 

 by the following comparison of the Temperatures obtained in the ' Porcu- 

 pine 5 Expeditions of 1869 and 1870, between 100 and 500 fathoms 



