All About Inventions and Discoveries
The Romance of modern scientific and mechanical Achievements

2i8 All About Inventions change. That of the negative rod assumes a point, while the extremity of the positive corrodes to form a crater-like hollow. Now, as these points burn, the length of the gap across which the current has to leap increases until at last it becomes so wide as to be beyond the capacity of the current. Accordingly, owing to the break in the circuit, illumination dies down. But the light can be re-established merely by bringing the two extremities into contact once more and then separating them by a short distance as before. The act of bringing the charcoal rods together to form electrical contact is known as “ striking ” the arc, and the flame continues all the while the gap between the two is kept fairly constant. To fulfil this latter necessity, however, a means had to be devised to feed the arcs together, thus preserving the length of the gap. While Humphry Davy’s fascinating experiment induced his contemporaries to carry out further in- vestigations along the line of research he had indicated, progress was conspicuously slow. Indeed, there were periods which seem to have been totally unproductive. It remained for another eminent British scientist to impart a new boost to thought and experiment in this channel. This was Michael Faraday, who twenty- years later, while he was director of the Royal Insti- tution, discovered and set forth the principle of electro-magnetic induction. Faraday not only talked but did things, in which he differed from many pioneers. He built a machine wherein his principles were ocularly demonstrated, and thus produced the first primitive dynamo, or, as it was then termed, magneto-electric machine.