Дитри COMPLETE TREATISE ΟΝ ELECTRICITY, IN THEORY AND PRACTICE; WITH ORIGINAL EXPERIMENTS. By TIBERIUS CAVALLO, F. R. S. THE THIRD EDITION, I N TWO VOLUMES, Containing the PRACTICE of MEDICAL ELECTRICITY, VOLUME II. LONDON: PRINTED FOR C. DILLY, IN THE POULTRY. M.DCC.LXXXVI. A COMPLETE TREATISE ON ELECTRICITY. PART IV. NEW EXPERIMENTS IN ELECTRICITY. HE laws of Electricity, together with TH the experiments neceffary for their demonstration, having already been describ→ ed, in as compendious a manner as could be done without obfcurity, I fhall, in the last Part of this Work, relate fuch new experiments and obfervations as I have made at different times, principally with a view to discover, if poffible, the unknown cause of feveral electrical phenomena, especially those relative to atmospherical Electricity. VOL. II. B 146368 The The first inftrument that I made use of to observe the Electricity of the atmosphere, was an electrical kite, which I had conftructed, not with a view to observe the Electricity of the air; for this, I thought, was very weak, and seldom to be obferved; but as an inftrument which could be occafionally used in time of a thunder-ftorm, in order to obferve the Electricity of the clouds. The kite, however, being just finished, together with its ftring, which contained a brass wire through its whole length, I raised it on the 31st of Auguft 1775, at feven of the clock in the afternoon, the weather being a little cloudy, and the wind juft fufficient for the purpose. The extremity of the string being infulated, I applied my fingers to it; which, contrary to my expectation, drew very vivid and pungent fparks: I charged a coated phial at the string several times, but I did not then obferve the quality of the Electricity. This fuccefsful experiment induced me to raise the kite very often, and to keep it up for feveral hours together; thinking that if any periodical Electricity, or any change of its quality, took place in the atmosphere, it might very probably be discovered discovered by this inftrument. In the following two Chapters I fhall describe the construction of the electrical kite, with its appurtenances; and fhall transcribe the moft remarkable part of my journal relative to the kite; i. e. describing such experiments only as are most remarkable, and do not happen very commonly; for although I have used my kite fometimes ten, and more times in a week, and at any hour of the day or night, yet as the greatest part of thofe experiments are only of use to confirm a few laws of atmospherical Electricity, I fhall omit their particular detail, and shall only fubjoin those laws at the end of the fecond chapter. |