WATSON'S ELECTRICAL THEORY.

535

Watson's "sequel" is dated October 20th, 1746, and was read before the Royal Society ten days later. Reduced to a few words, his theory is simply that the exciting of an electric causes the advent thereto of fire from the nearest adjacent conductor, and that the latter regains an amount equal to that lost. "By asserting," he adds, "that that we have hitherto called the effluvia does not proceed from the glass or other electrics per se, I differ from Cabæus, Digby, Gassendus, Brown, Descartes and the very great names of the last as well as the present age."

It may be conceded that Watson supposed that what he calls the elastic electric ether became more dense in one body and less dense in another; but it will be observed that there is no principle of equilibrium here involved. He imagined that the man touching the charged Leyden jar parted, immediately with his fire, and immediately regained it from the floor. But no matter how highly charged the jar, if, according to Watson's notion, he stood on a pitch cake, or even had dry soles to his shoes, the flux to him from the floor would thereby be prevented, and the jar would give him no shock-which is of course erroneous; for the man's body, no matter on what it is supported, obviously closes the circuit between the inside and outside of the jar.

Enough has now been stated to show what Watson's theory actually was in the fall of 1746. I shall recur to it hereafter.

The physical advance accomplished may now be noted. Van Musschenbroeck had found, and Watson had likewise recently re-verified the fact, that the thinner the glass of the jar the stronger the shock. Watson alone had found that the greater the area of the conductors in contact with the glass, again the stronger the shock. Two of the three conditions upon which depend the capacity of a condenser had thus been discovered: namely, the thinness of the dielectric stratum between the coatings, and the size of the coatings themselves. The third (specific inductive capacity of the dielectric) was still far in the future.

So much for the jar. Now as to the circuit. By midsummer of 1747, Watson had gained a comprehensive idea of the law of resistance, and states it thus:

"This circuit, where the non-electrics (conducting substances), which happen to be between the outside of the vial and its hook, conduct electricity equally well, is always described in the shortest route possible; but if they conduct differently, this circuit is always formed through the best conductor, how great soever its length is, rather than through one which conducts not so well, though of much less extent," in other words, he had established and now announced that the resistance of a conductor to the passage of electricity is proportional to its length, and, other things being equal, depends upon the material of which it is composed.

CHAPTER XVI.

THE printer's boy, who had landed hungry, footsore and all but penniless at the Market Street wharf in Philadelphia, after a hard journey by both sea and land from Boston, was now, twenty-three years later, the chief citizen of the growing town. To no one did that community then owe so much as it did to Benjamin Franklin.' The once runaway apprentice had organized its police, founded its school (destined afterwards to become one of the great universities of the world) devised for it a system of fire protection, established its Philosophical Society and its public library (the first in the colonies), printed its books and its newspapers, supplied it with concentrated worldly wisdom in the maxims of Poor Richard, served it in various official capacities, and invented for it the stoves to which it still clings. Of the magnificent services which he was later to render, not to his town, but to his country, Franklin, at forty years of age, had doubtless no anticipation. The time seemed to him near at hand when he might relinquish some of the many tasks imposed upon him-when the grind of money-getting might cease, and when with the modest fortune which tireless endeavor and patient frugality had brought to him, he might turn, not to idleness, but to work which, through the pleasure it afforded, bore no resemblance to toil. As his inclinations were to philosophic study, this it was now his ambition uninterruptedly to pursue.

'I have followed the autobiography of Franklin as edited by the Hon. John Bigelow, in his fine edition of Franklin's Works, N Y., 1889. Parton's Life and Times of Franklin, New York, 1864, has a chapter (vol. I, c. ix.) devoted to “Franklin and Electricity," but the errors in it are many. Weems' biography is chiefly a work of pure imagination.