He explained the laws of hot air and its movements; the Holland stove, which afforded but little ventilation; the German stove, which was simply an iron box fed from outside, with no ventilating properties; and the great open fireplace fed with huge logs, which required such a draft to prevent the smoke from coming back into the room that the outer door had to be left open,—and if the door was shut the draft would draw the outer air whistling and howling through the crevices of the windows. His “Pennsylvania Fireplace” was what we would now call an open-fireplace stove. It was intended to be less wasteful of fuel than the ordinary fireplace and to give ventilation, while combining the heating power of the German and Holland stoves. It continued in common use for nearly a century, and modified forms of it are still called the Franklin stoves.
One of its greatest advantages was that it saved wood, which, for some time prior to the introduction of coal, had to be brought such a long distance that it was becoming very expensive. Franklin refused to take out a patent for his invention; for he was on principle opposed to patents, and said that as we enjoyed great advantages from the inventions of others, we should be willing to serve them by inventions of our own. He afterwards learned that a London ironmonger made a few changes in the “Pennsylvania Fireplace” and sold it as his own, gaining a small fortune.
Franklin’s invention was undoubtedly an improvement on the old methods of heating and ventilation; but he was not, as has been absurdly claimed, the founder of the “American stove system,” for that system very soon departed from his lines and went back to the air-tight stoves of Germany and Holland.
It was not until 1746 or 1747, after he had been making original researches in science for about five years, that he took up the subject of electricity, and he was then forty-one years old. It appears that Mr. Peter Collinson, of London, who was interested in botany and other sciences, and corresponded largely on such subjects, had presented to the Philadelphia Library one of the glass tubes which were used at that time for producing electricity by rubbing them with silk or skin. Franklin began experimenting with this tube, and seems to have been fascinated by the new subject. On March 28, 1747, he wrote to Mr. Collinson thanking him for the tube, and saying that they had observed with its aid some phenomena which they thought to be new.
“For my own part, I never was before engaged in any study that so totally engrossed my attention and my time as this has lately done; for what with making experiments when I can be alone, and repeating them to my friends and acquaintance, who from the novelty of the thing, come continually in crowds to see them, I have, during some months past, had little leisure for anything else.”
It will be observed that he speaks of crowds coming to see the experiments, and this confirms what I have already shown of the strong interest in science which prevailed at that time in Pennsylvania, and which had evidently first aroused Franklin. In fact, a renewed interest in science had been recently stirred up all over the world, and people who had never before thought much of such things became investigators. Voltaire, who resembled Franklin in many ways, had turned aside from literature, and at forty-one, the same age at which Franklin began the study of electricity, had become a man of science, and for four years devoted himself to experiments.
Franklin was by no means alone in his studies. Besides the crowds who were interested from mere curiosity, there were three men—Ebenezer Kinnersley, Thomas Hopkinson, and Philip Syng—who experimented with him, and it was no mere amateurish work in which these men were engaged. Franklin was their spokesman and reported the results of his and their labor by means of letters to Mr. Peter Collinson. Within six months Hopkinson had observed the power of points to throw off electricity, or electrical fire, as he called it, and Franklin had discovered and described what is now known as positive and negative electricity. Within the same time Syng had invented an electrical machine, consisting of a sphere revolved on an axis with a handle, which was better adapted for producing the electrical spark than the tube-rubbing practised in Europe.
The experiments and the letters to Collinson describing them continued, and about this time we find Franklin writing a long and apparently the first intelligent explanation of the action of the Leyden jar. Then followed attempts to explain thunder and lightning as phenomena of electricity, and on July 29, 1750, Franklin sent to Collinson a paper announcing the invention of the lightning-rod, together with an explanation of its action.
In these papers he also suggested an experiment which would prove positively that lightning was a form of electricity. The two phenomena were alike as regarded light, color, crooked direction, noise, swift motion, being conducted by metals, subsisting in water or ice, rending bodies, killing animals, melting metals, and setting fire to various substances. It remained to demonstrate with absolute certainty that lightning resembled electricity in being attracted by points; and for this purpose Franklin proposed that a man stand in a sort of sentry-box on the top of some high tower or steeple and with a pointed rod draw electricity from passing thunder-clouds.
This suggestion was successfully carried out in France, in the presence of the king, at the county-seat of the Duke D’Ayen; and afterwards Buffon, D’Alibard, and Du Lor confirmed it by experiments of their own. But they did not use steeples; they erected lofty iron rods, in one instance ninety-nine feet high. Nevertheless, it was in effect the same method that Franklin had suggested. The experiment was repeated in various forms in England, and the Philadelphia philosopher, postmaster, and author of “Poor Richard” became instantly famous as the discoverer of the identity of lightning with electricity.