215 
remarkable Effects of a Shipwreck. 
of the surrounding medium unchanged, is, I think, fatal to 
those theories of animation which consider the living body as 
a mere machine, acted on by external powers, but not itself 
originating action, and differing from other machines only in 
the peculiarity of the powers which are fitted to set it in mo- 
tion. I have said that the temperature of the medium conti- 
nued unchanged, but it may be supposed that the bath was 
heated a little during the experiments ; it was so ; but being 
exposed, with a large surface, to the open air, the wind blow- 
ing briskly over it, its heat was little altered; in twelve mi- 
nutes immersion it had gained nearly one degree, and in forty- 
five minutes, the longest duration of any of the experiments, 
it had gained three degrees. As this accession was regular, if 
it had been greater it would not have invalidated the fore- 
going observations. 
Many other trials were made on the effects of immersion in 
water on the human heat, which I shall speak of generally, 
under the general conclusions which they suggested. 
The experiments already recited, suggested to me the no- 
tion that in all changes from one medium to another of different 
density, though of the same temperature, there is a loss of 
animal heat. I found, however, that this conclusion requires 
many restrictions. 
1. My experiments being made on bodies of such very 
different density as air and water, do not admit an universal 
inference of this sort. 
2 . Being all made in a temperature fifty degrees under the 
human heat, no certain conclusion can be drawn as to what 
might happen in degrees of heat much higher, where it is pro- 
bable, the effects of the change, if it appeared at all, might be 
Ff 2 
