298 On the Temperature of the Sea, 



immersion lasted seventy five minutes, the air was at -{-25°; the 

 surface of the water indicated -1-24° 8'. The thermometer drawn 

 up, and promptly taken out of its case indicated but +6°, that is to 

 say, nearly 19° less than the surface, an enormous difference, and 

 which truly had been more considerable still, if the extraction, which 

 took up three quarters of an hour, had not varied the temperature of 

 the apparatus ; that variance would however have been greater, if the 

 pressure of the water, always too strong for my securities against it, 

 had not introduced itself into its interior. In spite of those serious 

 inconveniences the result was uniform, the temperature of the sea 

 always decreased in exact proportion as the thermometer descended 

 in its bosom. What may be the ultimate limit of such decrease ? A 

 problem not less curious than important, the solution of which, in the 

 actual state of knowledge, does not appear as difficult as might at 

 first have been supposed. But as the strictness required in all new 

 experiments looks to the general concurrence of their results for evi- 

 dence of their value, let us examine what are those results obtained 

 by the men of science who have been occupied in the same object, 

 and in the same circumstances, that is to say, in the mid-ocean, far 

 from continents and islands. 



• If we except the celebrated traveller* whose return has rejoiced 

 all the friends of science, but whose discoveries are as yet unknown 

 to me, three persons only, have until this time, made experiments in 

 the main ocean in a similar manner to ascertain its temperature at 

 various depths, Forster, L'ving, and myself. By a singular and for- 

 tunate chance, our experiments have been repeated at three of the 

 most opposite points on the globe. Irving in Phipps' voyage towards 

 the north pole, made his at 80° of north latitude. Forster in Cooke's 

 expedition to the south pole, continued them to the 64° south, beyond 

 which no voyager has as yet been able to penetrate, and myself, placed 

 between those extremes, have made my experiments in the vicinity 

 of the equator. Certainly it would be difficult to find any other fact 

 in physics which would include terms of comparison taken at such 

 distances from each other ; and yet we shall see that all those ex- 

 periments give results analagous to those which I have described. 



* A. Humboldt. 



