পাতা:পদার্থবিদ্যাসার.djvu/৭১

60 fied, that it may become ten times as large as it was beforé; which you may have seen yourself, without, perhaps, having observed it in this light. The bubbles which children form with a pipe iuniuediately ascend, having then become lighter than air. Pup, But w hat is time principai «ause of the ascension of these vapo/irs from , i::- sea? Tut. The warmth and heat of the sun, by which the water is rarefied. Pup. if vapour is, thus raise«l from the sea, and formed into clouds, how is it that the rain is not sait when it descenais ? Tut. Because the saline particles of the water are heavier than time other parts, and the sum has not power sufficient to draw theim up with the vapour. Pup. ttow is it that heavy bodies sink, and light bodies swim, in water * Tus. A body. that is heavier than an equal boilk of a fluid, will sink in that fluid : a body that is lighter wiłł swim ; and a body of the same weight waii neither sink nor swim, but remain suspended. Pup. What is y our opinion of fire ? Tut. It is as necessary and useful as air and water. Pup. Where do you acquire it Tui. It lies hidden almost in every thing, because we have continual need of it. There it remains in a state of rest, called by philosophers latent heat; but when it is brought out of its latent state, it diffuses itself among all surrounding objects. It is lighter than air, as you may see from the velocity with which all flames ascend into the air. It inelts and softens the hardest metals, evaporates moisture, boils and roasts our