130 PHILOSOPHICAL TRANSACTIONS. [anNO 1764. 



the clouds, within the sphere of action of the apparatus, have by its operation 

 their electricity brought to the same standard with that of the earth in its neigh- 

 bourhood, and vice versS ; and consequently that the mischiefs which might arise 

 from the difference of the densities of the electricity in the earth and clouds are 

 prevented, by the equilibrium between them being maintained. This subject, 

 in regard to the electricity's being plus or minus, I many years ago considered, 

 and laid my thoughts on it before the public, as may be seen in the Phil. Trans., 

 vol. xlv. (Abridgement, vol. ix.) 



That the atmosphere at times is very strongly electrified is evident, to say no- 

 thing of lightning, not only from our apparatus, but from the masts of ships, 

 being beset with St. Elmo's fires, which I believe would scarcely, if ever happen, 

 were the masts provided with an apparatus of this sort; unless the cause might 

 be so great, and come on so fast, that the metal employed between the tops of 

 the masts and the water might not, on account of the vastness of the cause, be 

 large enough for the purpose. If it should so happen, St. Elmo's fires might 

 still appear at the tops of the masts, and thunder clouds might burst near them, 

 and exert their dreadful effects.* That even artificial electricity, when in too 

 great a quantity, and hurried on too fast through a fine iron wire, has a re- 

 markable effect on the wire, appears from a very curious experiment of Mr. 

 Kinnersley of Pennsylvania. This gentleman, in the presence of Dr. Franklin, 

 by his case of bottles being electrified fully, and made to explode at once, after 

 the manner of the experiment of Leyden, through a fine iron wire, the wire ap- 

 peared at first red-hot, and then fell into drops, which burned themselves into 

 the surface of his table or floor. These drops cooled in a spherical figure, like 

 very small shot, of which Dr. Franklin transmitted some hither to Mr. Can- 

 ton, 4- who had repeated this experiment. This proves the fusion to have been 

 very complete, as nothing less than the most perfect fluidity could give this 

 figure to melted iron. These effects from artificial lightning, are exactly similar 

 to those of the natural; as we have several times known iron wires, nails, and 

 other metallic substances to have been melted, and parts of them, while hot, 

 bedding themselves in wood by a thunder storm. Of this we had some instances 

 here in a thunder storm, which happened in July 1759, of which the effects 



* See more upon this subject, Phil. Trans-, Abridgment, vol. x. p. 372. 



f The diameter of a piece of Mr. Kinnersley's wire, which I received from Dr. Fraukhn, was one 

 ' part in 182 of an inch. Artificial lightning from a case of 35 bottles, I find will entirely destroy 

 brass wire of one part in 330 of an inch. At the time of the stroke, a great number of sparks, like 

 those from a flint and steel, fly upwards, and laterally from the place where the wire was laid, and 

 lose their light in the day-time at the distance of about 2 or 3 inches. After the explosion, a mark 

 appears on the table the whole length of the wire; and some very small round particles of brass may 

 be discovered, by a magnifier, near the mark} but no part of the wire itself can be found. J. Can- 

 ton.— Orig. 



