302 PHILOSOPHICAL TRANSACTIONS. [aNNO 1752. 



XCFI. A Letter from Mr. W. Watson, F. R. S. to the Royal Society, con- 

 cerning the Electrical Experiments in England on Thunder Clouds. Dattd 

 Dec. 20, J 752. p. 567. 



After the communications received from several correspondents in different 

 parts of the continent, acquainting us with the success of their experiments last 

 summer, in endeavouring to extract the electricity from the atmosphere during a 

 thunder storm, in consequence of Mr. Franklin's hypothesis, it may be thought 

 extraordinary that no accounts have been yet laid before the Society of our suc- 

 cess here from the same experiments. That no want of attention therefore may 

 be attributed to those here; who have been hitherto conversant in these inquiries, 

 he states, that though several members of the Royal Society, as well as himself, 

 did, on the first advices from France, prepare and set up the necessary apparatus 

 for this purpose, they were defeated in their expectations, by the uncommon 

 coolness and dampness of the air here, during the whole summer. They had 

 at London only one thunder storm; viz. on July 20; and then the thunder was 

 accompanied with rain; so that, by wetting the apparatus, the electricity was 

 dissipated too soon to be perceived on touching those parts of the apparatus 

 which served to conduct it. This in general prevented verifying Mr. Franklin's 

 hypothesis; but Mr. Canton was more fortunate, as appears by the following 

 letter from him to Mr. Watson, dated from Spital-square, July 21, 1752. 



" I had yesterday, about 5 in the afternoon, an opportunity of trying Mr. 

 Franklin's experiment of extracting the electrical fire from the clouds; and suc- 

 ceeded by means of a tin tube, between 3 and 4 feet in length, fixed to the top 

 of a glass one, of about 18 inches. To the upper end of the tin tube, which 

 was not so high as a stack of chimnies on the same house, I fastened 3 needles 

 with some wire; and to the lower end was soldered a tin cover to keep the rain 

 from the glass tube, which was set upright in a block of wood. I attended this 

 apparatus as soon after the thunder began as possible, but did not find it in the 

 least electrified, till between the 3d and 4th clap; when applying my knuckle to 

 the edge of the cover, I felt and heard an electrical spark; and approaching it a 

 2d time, I received the spark at the distance of about half an inch, and saw it 

 distinctly. This I repeated 4 or 5 times in the space of a minute; but the sparks 

 grew weaker and weaker ; and in less than 2 minutes the tin tube did not a[)pear 

 to be electrified at all. The rain continued during the thunder, but was consi- 

 derably abated at the time of making the experiment." 



Mr. Wilson likewise of the Society, to whom we are much obliged for the 

 trouble he has taken in these pursuits, had an opportunity of verifying Mr. 

 Franklin's hypothesis. He informed Mr. W, by a letter from near Chelmsford 

 in, Essex, dated Aug. 12, 1752, that on tluit day about noon, he perceival se- 



