The reason of this is, that we cannot feel warm till we have been cold, and _vice versa_." "Our bodies," resumed Fritz, "however much the thermometer descends, never mark less than thirty-five degrees above zero.

In winter the skin shrinks, and becomes a bad conductor of heat from without; but, at the same time, does not allow so much gas and vapor to escape from within.

In summer, on the contrary, the skin dilates and allows perspiration to form, a process that consumes a considerable amount of latent heat.

Starting from this principle, it has been calculated that a man, breathing twenty times in a minute, generates as much heat in twenty-four hours as would boil a bucket of water taken at zero." "If means could be found," remarked Jack, "to furnish him with a boiler, by fixing a piston here and a pipe there man might be converted into one of the machines we were talking about the other day." "Were I disposed to philosophize," added Fritz, "I might prove to you that for a long time men have been little else than mere machines." Before night they had run about thirty miles further to the north-east, without seeing any thing beyond a formidable bluff, guarded by a fringe of breakers, that would soon have swallowed up the _Mary_ had she ventured to reach the land.

It was necessary however to obtain fresh water at any price before they resumed their voyage.
It was to be feared that all the islanders of the Pacific were not in expectation of a great Rono, consequently Willis suggested that it would be as well to search for an uninhabited spot.