"That is because you are organized to live in air and not in water. You ask the smallest sprat or sticklebake if it does not, in the same way feel the air obstruct its progress."
"But would the stickleback answer me, Master Fritz?"
"Why not, if it is polite and well bred?"
"By the way, Willis," inquired Jack, "do you ever recollect having lived without breathing?"
"Can't say I do."
"Very well, then; had you felt the weight of the air at any given moment, it must have produced an impression you never felt before, but you have not, because circumstances have never varied. A sensation supposes a contrast, whilst, ever since you existed, you have always been subject to atmospheric pressure."
"Ah, now I begin to get at the gist of your argument. You mean, for example, that I would never have appreciated the delicate flavor of Maryland or Havanna, had I not been accustomed to smoke the cabbage-leaf manufactured in Whitechapel."
"Precisely so; and take for another example the farm of Antisana, which is situated about midway up the Cordilleras, mountains of South America. When travellers, arriving there from the summits which are covered with perpetual snow, meet others arriving from the plain where the heat is intense, those that descend are invariably bathed in perspiration, whilst those that have come up are shivering with cold and covered with furs. The reason of this is, that we cannot feel warm till we have been cold, and vice versâ."
"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."