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CHEMICAL AFFINITY.

collected in the other tube (O). Something is coming out of the water there (at H) which burns [setting fire to the gas], but what comes out of the water here (at O), although it will not burn, will support combustion very vigorously. [The Lecturer here placed a match with a glowing tip in the gas, when it immediately rekindled.]

Here, then, we have two things, neither of them being water alone, but which we get out of the water. Water is therefore composed of two substances different to itself, which appear at separate places when it is made to submit to the force which I have in these wires, and if I take an inverted tube of water and collect this gas (H), you will see that it is by no means the same as the one we collected in the former apparatus (fig. 24). That exploded with a loud noise when it was lighted, but this will burn quite noiselessly—it is called hydrogen; and the other we call oxygen—that gas which so beautifully brightens up all combustion, but does not burn of itself. So now we see that water consists of two kinds of particles attracting each other in a very different manner to the attraction of gravitation or cohesion, and this