. £ 568 ) 
dampnefs of the air here, during the whole fummer. 
We had only at London one thunder-dorm - t viz. 
on July 20 ; and then the thunder was accompanied 
with rain fo that, by wetting the apparatus, the 
electricity was diffipated too foon to be perceived 
upon touching thofe parts of the apparatus, which 
ferved to conduCt it. This, I fay, in general pre • 
vented our verifying Mr. Franklin’s hypothecs : but 
our worthy brother Mr. Canton was more fortunate. 
I take the liberty, therefore, of laying before you an 
extract of a letter, which I received from that gen- 
tleman, dated from Spital-fquare, July 21, 175*2. 
ct I had yefterday, about five in the afternoon, an 
“ opportunity of trying Mr. Franklin’s experiment 
u of extracting the electrical fire from the clouds j 
u and fucceeded, by means of a tin tube, between 
“ three and four feet in length, fixed to the top of 
“ a glafs one, of about eighteen inches. To the up- 
<c per end of the tin tube, which was not fo high 
u as a flack of chimnies on the fame houfe, I fattened 
“ three needles with fome wire ; and to the lower 
“ end was folder’d a tin cover to keep the rain from 
“ the glafs tube, which was fet upright in a block 
“ of wood. I attended this apparatus as foon after 
u the thunder began as poffible, but did not find it 
“ in the lead electrified, till between the third and 
“ fourth clap ; when applying my knuckle to the 
“ edge of the cover, I felt and heard an electrical 
<£ fpark ; and approaching it a fecond time, I re- 
u ceived the lpark at the diflance of about half an 
u inch, and faw it didinctly. This I repeated four 
u or five times in the fpace of a minute ; but the 
" fparks 
