"Why, the word heat has two meanings, uncle. In the first place, it means hotness. Hotness can not be latent, as the clown finds when he pockets the poker. In the second place, heat means a something the nature of which we don't know, which is the cause of hotness, and also the cause of another effect. While it is causing that other effect, it does not cause hotness. That other effect which heat causes in the instance of steam, is keeping water in the form of steam. The heat that there is in steam, over and above two hundred and twelve degrees, is employed in this way. It is wholly occupied in preserving the water in an expanded state, and can't cause the mercury in the thermometer to expand and rise as well. For the same reason, it could give you no feeling of hotness above what boiling water would--if you had the nerve to test it. While it is making steam continue to be steam, it is latent. When the steam becomes water again, it has no longer that work to do, and is set free. Free heat is what is commonly understood by heat. This is the heat which cooks our victuals, the heat we feel, the heat that singes Mr. Merriman. Latent heat is heat that doesn't warm, singe, or cook, because it is otherwise engaged. If you press gas suddenly into a fluid, the latent heat of the gas is set free. You seem to squeeze it out. Indeed, the same thing happens, if you violently force any substance into a closer form all at once. Every thing appears to have more or less latent heat in it, between its little particles, keeping them at certain distances from each other. Compress the particles within a smaller compass, and a part of the latent heat escapes, as if it were no longer wanted. When a substance in a compressed state expands on a sudden, it draws in heat, on the other hand. When a lady bathes her forehead with eau-de-Cologne to cure a headache, the heat of the head enters the eau-de-Cologne, and becomes latent in it while it evaporates. If you make steam under high pressure, you can heat it much above two hundred and twelve degrees. Suppose you let off steam, so compressed and heated, by a wide hole, from the boiler, and put your hand into it as it rushes out--" "What? Why, you'd scald your hand off!" cried Mr. Bagges. "No, you wouldn't. The steam rushes out tremendously hot, but it expands instantly so very much, that the heat in it directly becomes latent in a great measure; which cools it down sufficiently to allow you to hold your hand in it without its hurting you. But then you would have to mind where you held your hand; because where the steam began to condense again, it would be boiling hot." "I had rather take your word for the experiment than try it, young gentleman," Mr. Bagges observed.