448 DR. DAVY ON THE TEMPERATURE OF MAN WITHIN THE TROPICS. 
11. That the tendency of a sea voyage, apart from sea-sickness, is to equalize the 
temperature without elevating it, an equalization that is best witnessed in voyaging 
in a tropical sea, where the atmospheric temperature is so little variable. 
12. That even at sea, with a change of atmospheric temperature, there is a ten- 
dency to change of temperature of the body, the average increasing in proceeding 
towards the tropics, and diminishing in receding from them. 
These conclusions obviously admit of application, and that variously in relation to 
health and disease. It would be unsuitable to the occasion to dwell on this part of 
the subject; I shall merely remark, that it is a happy circumstance for man, and 
seems wisely ordered, that fluctuation of temperature should be connected with a 
healthy state of the system, and probably conducive to it, in whatever manner pro- 
duced, whether by change of climate, or atmospheric variation, or by exercise, whe- 
ther of body or mind. The excellent health which the crews of the West Indian 
steam-packets have, that are in constant transition from heat to cold, is a striking 
proof of this, and other instances of a like kind, were it necessary, might be adduced 
in confirmation. 
Lesheth How, Amhleside, 
February 14 , 1850 . 
