Fig. 3. Apparatus for preparing & collecting hydrogen gas.
Fig. 4. Receiver full of hydrogen gas inverted over water.
Fig. 5. Slow combustion of hydrogen gas.
Fig. 6. Apparatus for illustrating the formation of water by the combustion of hydrogen gas.
Fig. 7. Apparatus for producing harmonic sounds by the combustion of hydrogen gas.

[Larger view] (complete Plate)

EMILY.

How very rapidly the gas escapes! it is perfectly transparent, and without any colour whatever.—Now the receiver is full——

MRS. B.

We shall, therefore, remove it, and substitute another in its place. But you must observe, that when the receiver is full, it is necessary to keep it inverted with the mouth under water, otherwise the gas would escape. And in order that it may not be in the way, I introduce within the bath, under the water, a saucer, into which I slide the receiver, so that it can be taken out of the bath and conveyed any where, the water in the saucer being equally effectual in preventing its escape as that in the bath. ([Plate VIII.] fig. 4.)

EMILY.

I am quite surprised to see what a large quantity of hydrogen gas can be produced by such a small quantity of water, especially as oxygen is the principal constituent of water.

MRS. B.

In weight it is; but not in volume. For though the proportion, by weight, is nearly six parts of oxygen to one of hydrogen, yet the proportion of the volume of the gases, is about one part of oxygen to two of hydrogen; so much heavier is the former than the latter.