“Why, what happens, uncle, when we take violent exercise? We break out into a perspiration; as you complain you always do, if you only run a few yards. Perspiration is mostly water, and the extra heat of the body goes into the water, and flies away with it in steam. Just for the same reason, you can’t boil water so as to make it hotter than two hundred and twelve degrees; because all the heat that passes into it beyond that, unites with some of it and becomes steam, and so escapes. Hot weather causes you to perspire even when you sit still; and so your heat is cooled in summer. If you were to heat a man in an oven, the heat of his body generally wouldn’t increase very much till he became exhausted and died. Stories are told of mountebanks sitting in ovens, and meat being cooked by the side of them. Philosophers have done much the same thing—Dr. Fordyce and others, who found they could bear a heat of two hundred and sixty degrees. Perspiration is our animal fire-escape. Heat goes out from the lungs, as well as the skin, in water; so the lungs are concerned in cooling us as well as heating us, like a sort of regulating furnace. Ah, uncle, the body is a wonderful factory, and I wish I were man enough to take you over it. I have only tried to show you something of the contrivances for warming it, and I hope you understand a little about that!” “Well,” said Mr. Bagges, “breathing, I understand you to say, is the chief source of animal heat, by occasioning the combination of carbon and hydrogen with oxygen, in a sort of gentle combustion, throughout our frame. The lungs and heart are an apparatus for generating heat, and distributing it over the body by means of a kind of warming pipes, called blood-vessels. Eh?—and the carbon and hydrogen we have in our systems we get from our food. Now, you see, here is a slice of cake, and there is a glass of wine—Eh?—now see whether you can get any carbon and oxygen out of that.” The young philosopher, having finished his lecture, applied himself immediately to the performance of the proposed experiment, which he performed with cleverness and dispatch. THE STEEL PEN. AN ILLUSTRATION OF CHEAPNESS. (FROM DICKENS’S HOUSEHOLD WORDS.) We remember (early remembrances are more durable than recent) an epithet employed by Mary Wolstonecroft, which then seemed as happy as it was original—“The _iron_ pen of Time.” Had the vindicatress of the “Rights of Women” lived in these days (fifty years later), when the iron pen is the almost universal instrument of writing, she would have bestowed upon Time a less common material for recording his doings.