A man named Nicholson had attached a wire to the bottom plate of one of the piles, and brought the other end into contact with the top plate. In order to improve the contact, he put a drop of water on the plate just where the wire touched it. He then observed that very small bubbles appeared in the drop of water, and although the quantity of the gas produced was very small, he thought it smelt of hydrogen. He at once tried the experiment of attaching two brass wires to the upper and lower end of the pile, and bringing them side by side into water, without touching each other. He then found that small bubbles were given off at one wire, and that the other was eaten away. He collected the bubbles of gas, and found that when it was mixed with air it exploded on bringing a lighted match to it. This proved that the water had indeed been broken up into two gases called oxygen and hydrogen. It was the first service to which the newly discovered electric current was put. CHAPTER XI THE ELECTRIC TELEGRAPH WHEN two persons engage in ordinary conversation, they really use two methods of communication. Both methods are extremely complicated. By means of mouth, tongue, and throat, the speaker changes the current of air issuing from his lungs, and throws it into a great variety of vibrations. These vibrations are communicated to the outside air and find their way into the ears of the other person. Such is speech. At the same time, people when speaking employ signals which appeal to the eye. They move their lips, eyelids, eyebrows, and sometimes their hands, and each motion gives a slightly different quality, or stress, to what they are saying. These motions produce an effect upon the waves of light which are constantly passing to and fro between the two people. In this way speech is assisted by sight. When two persons are far apart and still wish to communicate they have to shout. When the distance becomes greater, their voices become less and less able to cover it, and, finally, they are driven to communicate by sight only. So, we find them waving their hands, or handkerchiefs, or hags at the end of sticks. When the distance is many miles, this method fails again, and communication becomes very difficult. In ancient times people used to get out of the difficulty by lighting big fires which could be seen for ten or fifteen miles in the dark. The smoke from the fire could be seen for about the same distance in the day-time. Some savage tribes use the same method even now, and manage to convey a great deal of information by it. But nowadays we use the electric telegraph for all such purposes, and the story of its invention is one of great interest.