298 On the Temperature of the Sea, 
immersion lasted seventy five minutes, the air was at +2595 the 
surface of the water indicated +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 m 
‘the main ocean in.a similar manner to ascertain its temperature at 
various depths, Forster, Irving, 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 viemity 
of the equator. Certainly it would be difficult to find any other fact 
in physics whicli 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. 
