THE electric machine was used for extracting what was called the “electric fluid” out of a body by rubbing. The fluid in its passage through the air made a spark and a noise. It pricked the finger. In larger quantities it gave a severe shock, sufficient to kill small animals. In the form of lightning it killed men. Franklin called the fluid the “electric fire,” and supposed that it was a very subtle and delicate fluid distributed through all nature, and was the reason and cause of all electric happenings. When he found that two silk threads when charged with electricity repelled each other, he came to the conclusion that one portion of the electric fluid repels any other portion. When one body was rubbed against another he supposed that some of the fluid was extracted from one and absorbed by the other, but that after the exchange the two bodies attracted each other in proportion to the amount of electric fluid which had been extracted. There was, therefore, both an electric attraction and an electric repulsion. The attraction existed between the electric fluid and a body which had lost its ordinary quantity of that fluid. The repulsion took place between the portion of the fluid itself, and also between two portions of matter which had both been deprived of some of their electric fluid. Franklin believed that the whole science of electricity could be built up by studying the motion and distribution of the electric fluid. Franklin also tried to find out whether a body, after losing some of its natural quantity of electric fluid, weighs less than before, but he could not find any difference in weight. This result made him think that the electric fluid had no weight. He knew the difference between conductors of electricity and bodies which did not conduct it. He supposed that conductors could take up a great quantity of the fluid, and store it away in the interior of their substance. He knew that not more than a certain quantity of electricity could be extracted from a body however hard it was rubbed. He supposed that the amount of electricity in a body was limited, and that after some rubbing the limit was arrived at. The fact that the electric machine gave a constant supply of electricity he explained by supposing that the electricity returns to it through the air. There was, therefore, a constant circulation of electricity, a kind of electric current. But in Franklin’s time there was no way of producing a really steady current of electricity.