1869.] on the Scientific Exploration of the Deep Sea. 407 



namely at Station 87 in Lat. 59° 35' (more than 10° to the north of 

 Station 42), the same general accordance presents itself in the rate of de- 

 scent ; while the actual temperatures at the several depths below 100 fa- 

 thoms are by no means as different as might be expected from the differ- 

 ence in the geographical position of the Stations, as will be apparent from 

 the following Table : — 



Table IV. 



Comparative Rates of Reduction of Temperature with Increase of Depth, 

 at three Stations in different Latitudes, all of them on the Eastern Mar- 

 gin of the Atlantic Basin. 





Station 42. 



Station 23. 



Station 87. 



Depth. 



Lat. 49 c 



12'. 



Lat. 56 c 



13'. 



Lat. 59° 35'. 





Temperature. 



Difference. 



' Temperature. 



Difference. 



Temperature. 



Difference. 



fathoms. 



o 





0 





0 





Surface 



626 



0 



57*3 





5*'5 



0 







II- 5 





8°8 





5-2 



IOO 



$1"! 





48-5 





47'3 









o-6 





0-5 





°'5 





5°'5 





48-0 





46-8 









0-9 





0*2 





0'2 





49-6 





47-8 





46-6 









i*i 





0-3 









48-5 





47'5 





46 , i 







467 



18 





«7 





ro 



500 





458 





45 -1 









12 





-•3 





21 



600 



45-5 





44' 5 





43'o 









3-0 











75° 



42 5 











16 



767 











41-4 





Although the difference between the Surface-temperatures at Stations 

 42 and 87 amounts to 10°-1, the difference is reduced to 3°*8 at 100 

 fathoms, to 3° at 300 fathoms, to 2°-5 at GOO fathoms, and to 1°-1 at 

 750 fathoms. So, again, the reduction in the first 100 fathoms at Sta- 

 tion 87 being only 5°'2, the total reduction between 100 and 500 fathoms 

 is only 2°'2, or at the rate of 0°55 per 100 fathoms. But the rate of de- 

 pression then undergoes nearly as marked an increase as at the corre- 

 sponding depth in Station 42 ; for whilst the diminution of temperature 

 between 500 and 750 fathoms amounts at Station 42 to 4°*2, or 1 0, 7 per 

 100 fathoms, it amounts at Station 87 to 3°'7, or 1°'5 per 100 fathoms. 



111. It becomes obvious, therefore, in the first place, that there is a de- 

 cided superheating of the superficial stratum, not extending to a depth much 

 greater than 70 or 80 fathoms, and that this is more considerable (as might 

 be expected) at the Southern than at the Northern stations. Whether this 

 " superheating " is entirely due to the direct influence of solar heat, or de- 

 pends in any degree (especially in the southern portion of this area) on an 



