"Besides these great principles Franklin's letters on electricity contain a number of facts and hints which have contributed greatly toward reducing this branch of knowledge to a science. His friend, Mr. Kinnersley, communicated to him a discovery of the different kinds of electricity excited by rubbing glass and sulphur. This was first observed by M. du Faye, but it was for many years neglected. The philosophers were disposed to account for the phenomena rather from a difference in the quantity of electricity collected, and even Du Faye himself seems to have at last adopted this doctrine. Franklin at first entertained the same idea, but upon repeating the experiments he perceived that Mr. Kinnersley was right, and that the _vitreous_ and _resinous_ electricity of Du Faye were nothing more than the _positive_ and _negative_ states, which he had before observed, and that the glass globe charged positively, or increased, the quantity of electricity on the prime conductor, while the globe of sulphur diminished its natural quantity, or charged negatively. These experiments and observations opened a new field for investigation, upon which electricians entered with avidity; and their labors have added much to the stock of our knowledge. "Franklin's letters have been translated into most of the European languages, and into Latin. In proportion as they have become known, his principles have been adopted." In speaking of the first publication of his papers on electricity, Franklin himself says: "Obliged as we were to Mr. Collinson for the present of the tube, etc., I thought it right he should be informed of our success in using it, and wrote him several letters containing accounts of our experiments. He got them read in the Royal Society, where they were at first not thought worth so much notice as to be printed in their _Transactions_. One paper, which I wrote to Mr. Kinnersley, on the sameness of lightning with electricity, I sent to Mr. Mitchel, an acquaintance of mine, and one of the members also of that society, who wrote me word that it had been read, but was laughed at by the connoisseurs. The papers, however, being shown to Dr. Fothergill, he thought them of too much value to be stifled, and advised the printing of them. Mr. Collinson then gave them to Cave for publication in his _Gentleman's Magazine_, but he chose to print them separately in a pamphlet, and Dr. Fothergill wrote the preface. Cave, it seemed, judged rightly for his profession, for by the additions that arrived afterward they swelled to a quarto volume, which has had five editions and cost him nothing for copy-money." The following is an extract from the preface to the first edition of the pamphlet published by Cave, as above mentioned: