Table of Voltaic circles of the second order, composed of two imperfect conductors, and one perfect con

I will now show you another experiment which is to be made with the assistance of the great battery (Fig. 22.) A B (Plate VIII. Fig. 23.) exhibits a glass tube, filled with distilled water, and having a cork at each end. A and B are two pieces of brass wire, which are brought to within an inch or two of one another in the tube, and the other ends are carried to the battery, viz. A to what is called the positive end, and B to the negative end.

James. You have then positive and negative Voltaism, as well as electricity?

Tutor. Yes, and if the circuit be interrupted, the process will not go on. But if all things be as I have just described, you will see a constant stream of bubbles of gas proceed from the wire B, which will ascend to the upper part of the tube. This gas is found to be hydrogen or inflammable air. Charles. How is that ascertained?

Tutor. By bringing a candle close to the opening when I take out the cork a, the gas will immediately inflame. The bubbles which proceed from the wire A are oxygen or pure air, they accumulate and stick about the sides of the tube.

James. How is this experiment explained? Tutor. It is believed that the water is decomposed or divided into hydrogen and oxygen: the hydrogen is separated from the water by the wire connected with the negative extremity, while the oxygen unites with and oxidates the wire connected with the positive end of the battery.

If I connect the positive end of the battery with the lower wire, and the negative with the upper, then the hydrogen proceeds

from the upper wire, and the lower wire is oxidated.

If wires of gold or platina be used which are not oxidable, then a stream of gas issues from each, which may be collected, and will be found to be a mixture of hydrogen

and oxygen.

Charles. Are there no means of collecting these fluids separately:

Tutor. Yes, instead of making use of the tube, let the extremities of the wires, which proceed from the battery, be immersed in water, at the distance of an inch from each other, then suspend over each a glass vessel, inverted and full of water (Plate VIII. Fig. 24.) and different kinds of gas will be found in the two glasses.

It is known that hydrogen gas reduces the oxides of metals, that is, restores them to their metallic state. If, therefore, the tube (Fig. 23.) be filled with a solution of acetite of lead* in distilled water, and a communication is made with the battery, no gas is perceived to issue from the wire,

Acetite of lead, is a solution of lead in acetous acid.

which proceeds from the negative end of the battery, but in a few minutes, beautiful metallic needles may be seen on the extremity of this wire.

James. Is this the lead separated from the fluid?

Tutor. It is; and you perceive it is in a perfect metallic state, and very brilliant. Let the operation proceed, and these needles will assume the form of fern, or some other vegetable substance.

The spark from a Voltaic* battery acts with wonderful activity upon all inflammable bodies, and experiments made in a dark room, upon gun-powder, charcoal, metallic wire, and metallic leaves, &c. may be made very amusing.

* Mr. Davy has, by means of a very powerful battery, been enabled to decompose the alkalies, many of the earths, sulphur, phosphorus, and charcoal; also the boracic, fluoric, and muriatic acids. His first experiments were on potash and soda, which instead of being simple substances are found to consists of certain metallic substances and oxygen. See Dialogues on Chemistry.

CONVERSATION XLVII.

Miscellaneous Experiments.

TUTOR. The discoveries of Galvani were made principally with dead frogs; from his experiments, and many others that have been made since his time, it ap pears that the nerves of animals may be aflected by smaller quantities of electricity than any other substances with which we are acquainted. Hence limbs of animals, properly prepared, have been much employed for ascertaining the Voltaic electricity. Charles. What is the method of preparation.

Tutor. I have been cautious in mentioning experiments on animals, lest they