The reward for all this activity was that at the end of twenty years Benjamin Franklin had accumulated a handsome fortune, his average income amounting to over two thousand pounds sterling a year: then considered a very large sum, and of probably three times the purchase value it would possess at the present day. With increasing wealth, the active printer, happy in all his family relations, thought himself justified to seek a little occasional leisure, which he found chiefly in visits to Boston, his native town. It was on one of these visits, made in the summer of 1746, that he went with a friend to a lecture-hall, scarcely knowing what was to be the intellectual entertainment prepared for him. It proved a discourse, with illustrative experiments, upon electricity, by a Dr. Spence, duly armed with a three-feet glass rod and silk pocket-handkerchief. Benjamin Franklin was not merely interested: he was startled. It was to him, as he afterwards declared to one of his friends, the opening of a new world. Perhaps the subject which attracted so suddenly the attention of Benjamin Franklin might have escaped it again, in the pursuit of his many vocations, but for another accidental circumstance. It so happened that, immediately after his return to Philadelphia, there came a parcel of books from England, accompanied by a present in the shape of an electrical tube. The sender of it was the London agent of the Library Company of Philadelphia, Mr. Peter Collinson, a member of the Royal Society, and as such sharing the general interest in the electrical experiments of Dr. Watson. The tube, which was accompanied with full directions for its use, was no sooner unpacked, than Franklin seized it eagerly and began experimenting, at the same time inspiring the most sanguine of his friends to follow his example. Glass tubes, made similar to the one sent from London, were soon procured from a local manufacturer, and then began a general rubbing. ‘I never before,’ Franklin wrote, early in 1747, ‘was 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 acquaintances, 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.’ To the greater number of those friends and acquaintances who came flocking in crowds to the shop of the Philadelphia printer, the electric tube was, probably, only looked upon as a new toy; but it was vastly different as regarded himself. His keen practical eye seemed to discern at once that the manifestations of the mysterious force on which he was experimenting contained the germ of something that might be utilised by men, or brought into obedience to the human will.