378 PHILOSOPHICAL TRANSACTIONS. [anNO 1753. 



experiment on thunder. " In the night, says the author of those memoirs, 

 on a sudden it became exceedingly dark, and thundered and lightned most dread- 

 fully. As we were threatened with the ship's being torn to pieces, I ordered the 

 sails to be taken in : we saw, on different parts of the ship, above 30 St. Helmo's 

 fires ; among the rest, there was one on the top of the vane of the main-mast, 

 which was more than a foot and half in height. I ordered one of the sailors to 

 take it down ; when this man was on the top, he heard this fire ; its noise re- 

 sembled that of fired wet gunpowder. I ordered him to lower the vane, and 

 come down ; but scarcely had he taken it from its place, but the fire left it, and 

 fixed itself on the top of the mainmast, from which it was impossible to remove 

 it ; and it continued there a considerable time, till it gradually went out, &c." 



If all the authors, who have taken notice of St. Helmo's fire, had spoken of 

 it as this just quoted, philosophers might have reproached themselves for its 

 having been so long before they had a just idea of it, and for their not having 

 shown the principle on which it depended. But how few historians are there, 

 who could have related this fact with circumstances so proper to put us in a right 

 train, as those just mentioned .'' 



" And here I cannot but observe, as I am convinced, that the matter of thun- 

 der and that of electricity are one and the same, how vast an idea must the 

 attending to the before-mentioned passage excite in the mind of persons, accus- 

 tomed to the phenomena of electricity ? How immense a quantity of it must they 

 conceive to have been at that time in the atmosphere surrounding the ship, and 

 within the verge of its action, to furnish more than 30 St. Helmo's fires ; the 

 same in fact which we see at the ends of our conductors in electrizing, one of 

 which was more than a foot and half in height ? At this time, and under these 

 circumstances, the mast, yards, and every part of the ship, I consider as con- 

 ductors of electricity, between the then electrized atmosphere, and the sea ; and 

 though, being of a vegetable nature, and, if dry, even of the worst kind for this 

 purpose, they conducted electricity much less perfectly than metal under the like 

 circumstances would have done, I doubt not but that they were greatly instru- 

 mental in averting the danger, with which the ship was threatened. 



" On these considerations, I do not scruple to recommend, as Mr. Franklin 

 has done, communications of metal between the spindles and iron-work at the 

 tops of the masts of ships, and the sea ; or, which will answer the same purpose, 

 the bilge water in the well. This can be liable to little objection, as the doing it 

 is neither difficult nor expensive ; an iron wire, of the thickness of a goose- 

 quill, conducting electricity more readily than any piece of timber, however 

 large ; and these masts do it so much the worse, as they are of a resinous nature. 



•' From attending to these phenomena, we every day see more and more the 



