69 



perature it had under the tropics. Tbe great- 

 ness of the mass, and the small conductibility of 

 water for heat, prevent a more speedy refrigera- 

 tion. If therefore the Gulf-stream has dug a 

 channel at the bottom of the Atlantic ocean, and 

 if it's waters are in motion to considerable depths, 

 they must also in their inferior strata keep up a 

 lower temperature than that which is observed 

 in the same parallel, in a part of the sea which 

 has neither currents nor deep shoals. These 

 questions can be cleared up only by direct expe- 

 riments, made by thermometrical soundings. 



Sir Erasmus Gower remarks, that, in the pas- 

 sage from England to the Canary Islands, the 

 current, which draws the vessels towards the 

 south-east, begins at the 39th degree of latitude. 

 During our navigation from Corunna to the 

 coasts of South America, the effect of this motion 

 of the waters was perceived farther to the north. 

 From the 37th to the 30th degree, the deviation 

 was very unequal ; the daily average effect was 

 12 miles, that is, our sloop drove towards the 

 east 75 miles in six days. In cutting the parallel 

 of the Strait of Gibraltar, at a distance of 140 

 leagues, we had occasion to observe, that in 

 those latitudes, the maximum of the rapidity 

 does not correspond with the mouth of the Strait, 

 but with a more northerly point, which lies in 

 the prolongation of a line passing through the 

 Strait and Cape St. Vincent. This line is parallel 



