Page:On the various forces of nature and their relations to each other.djvu/27

Rh for instance, is some quick-lime, and if I add some water to it, you will find another power or property in the water. It is now very hot, it is steaming up, and I could perhaps light phosphorus or a lucifer match with it. Now, that could not happen without a force in the water to produce the result; but that force is entirely distinct from its power of falling to the earth. Again, here is another substance [some anhydrous sulphate of copper ] which will illustrate another kind of power. [The Lecturer here poured some water over the white sulphate of copper, which immediately became blue, evolving considerable heat at the same time.] Here is the same water, with a substance which heats nearly as much as the lime does; but see how differently. So great indeed is this heat in the case of lime, that it is sufficient sometimes (as you see here) to set wood on fire; and this explains what we have sometimes heard, of barges laden with quick-lime taking fire in the middle of the river, in consequence of this power of heat brought into play by a leakage of the water into the barge. You see how strangely different subjects for our