1872.] 



i Shearwater y Scientific Researches. 



515 



depth, at four Stations having an extreme range of 23° of Latitude, — the 

 first of these stations being off the coast of Portugal, the second about 

 240 miles to the S.W. of Cork, the third about 100 miles south of 

 Rockall, and the fourth about 120 miles to the N.W. of Stornoway 2 — 





I. 



N. Lat. 

 361°. ' 



II. 

 N. Lat. 

 49°. ' 



III. 

 N. Lat. 

 56°. ' 



IV. 

 ]S T . Xat. 

 59£°. ' 



Ext rem © 

 difference 

 between I. 

 and IV. ' 



Air .... - 



70 



o 



63 



58 



54 



o 



16 





68 



62-6 



57*3 



52-6 



15-4 



100 fathoms 



577 



51*1 



48-5 



47-3 



104 



200 „ 



55 



50-5 



48 



46-8 



8'2 



300 „ 



53 



49-6 



47-8 



46-6 



6-4 



400 „ 



52 



48-5 



47'5 



46-1 



5-9 



500 „ 



51-5 



47-4 



45-8 



45-1 



6-4 



Difference between 1 

 100 and 500. . J 



62 



37 



27 



2-1 





Now in the first place it is to be noted how closely the Temperature of 

 the surface of the Sea corresponds with that of the Air ; the reduction of 

 both, in passing northwards, being at almost precisely the same rate, and 

 the extreme differences being nearly identical. Next it will be observed 

 that these differences diminish in amount from above downwards, showing 

 that as the influence of insolation (which is for the most part restricted to 

 100 fathoms' depth) is lost, there is an increasing tendency to uniformity 

 of temperature. This influence extends the deepest, as might be expected, 

 at the southernmost station; the range between 100 and 500 fathoms 

 being there 6°*2, whilst at the northernmost station it is only 2 0, 1. But 

 while the temperatures at Station I. from 100 to 500 fathoms so nearly 

 correspond with the uniform temperature of the Mediterranean between 

 the same depths as to justify our assuming this to be nearly the normal of 

 the Latitude, but little modified by the convection either of heat or of cold 

 from any extraneous source (§ 8), the temperature at Station IV. of the 

 whole stratum of water between 100 and 500 fathoms is so much above 

 the normal of its Latitude as clearly to depend upon a translation of 

 warm water from a Southern area. And when we compare these extremes 

 with the intermediate temperatures of corresponding strata at Stations II. 

 and III., we see how regularly gradational is the transition ; the rate of 

 diminution being about half & degree (Fahr.) for every degree of Latitude 

 at 100 fathoms, and coming down to little more than a quarter of a degree 

 between 300 and 500 fathoms. The inference seems unavoidable, that the 

 entire stratum of water down to at least 500 fathoms has flowed northwards 

 to the parallel of 59^° from some lower parallel, losing heat in its way by 

 imparting it to the air above ; that loss of heat being chiefly shown in 



