Laying down the paper, and shaking him kindly by the hand, he said, “Tell me, Lewis, what do you imagine water to be?” “I suppose,” said Lewis, “it is a simple fluid. I mean, papa, that it is not composed of several ingredients; unless it be the water of the ocean, which you know is very salt; and sometimes part of the soil through which water runs, mixes with it and changes its colour.” “Many substances,” said his father, “were once thought to be simple, which the knowledge of chemistry has since taught us are formed by the union of other bodies, very opposite in their natures—water is one of these: you will understand more of its properties, I hope, when we have time to study chemistry together. But now I will only tell you, that water is composed of two airs or gases; one of them is lighter than any substance we are acquainted with; it is very inflammable, and burns when flame is applied to it; the other is that part of the atmosphere which is absolutely necessary to the existence of living creatures, whether in air or water. These two gases form water, by combustion.” “How wonderful!” exclaimed Lewis, “for water, you know, papa, extinguishes fire.” “It is, indeed, astonishing, Lewis: there is no end to the wonders which the knowledge of chemistry reveals, and no doubt will continue to reveal to us. But, now tell me, Lewis, have you ever seen water in any other than a fluid state?” “Oh! yes, papa, frozen water is quite solid; it then becomes ice.” “And,” interrupted Helen, “heated water becomes steam or vapour; though I recollect mamma’s telling me, that it was a fluid still; and that even the air which surrounds us is a fluid, like water, only much less dense; for when I moved her fan backwards and forwards, I could feel the resistance of the air very plainly.” “Well done, my little philosopher!” exclaimed Mr. Ashton. “Lewis, I dare say you have not forgotten all this.” “Oh! no papa,” said Lewis, “I often wish those days would come again, when Edward and I were always at home with you, and when we used to try experiments together.” “Well, Lewis, such days may come again,” said his father; “but, now let us attend to the present subject. To make it clearer to you, I must ask you one more question about our experiments:—do you recollect what took place when I held a cold plate, for some time, over the boiling water in the tea-urn?” “Yes, papa,” answered Lewis, “the steam which rose from the urn was condensed; for, as you said, the particles, which had separated, again united as soon as they came in contact with the cold plate, and ran off in little streams of water.” “And what caused the separation of the particles of water?” inquired his father. “Heat,” said Lewis, “and cold, which you told us means only the absence of heat, caused them to unite again.”