Page:Various Forces of Matter.djvu/22

10 water]. What a wonderful thing it is to see that it requires so much water as that [a half-pint vessel full] to fall towards the earth, compared with the little mass of substance I have here! And again, if I take this metal [a bar of aluminium about eight times the bulk of the platinum] we find the water will balance that as well as it did the platinum; so that we get even in the very outset, an example of what we want to understand by the words forces or powers.

I have spoken of water, and first of all of its property of falling downwards:—you know very well how the oceans surround the globe—how they fall round the surface, giving roundness to it, clothing it like a garment; but, besides that, there are other properties of water. Here, for instance, is some quicklime, 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