C 390 ] 
A Letter to the Reverend Dr . Birch, Secre- 
tary to the Royal Society , concerning the 
Force of eleElrical Cohefion . 
S I R, 
Read Dec. 20.^ Happened to be at Mr. Symmer’s on 
JL Saturday the 15-th inftant, when he 
defired me to be witnefs to fome electrical experi- 
ments, he was about to make, with filk (lockings, 
of a particular kind, which he had received for that 
purpofe. 
The weather was then remarkably favourable for 
electricity, being clear- and dry, with a (harp froft, 
which had continued five or fix days. The wind 
was eafterly, and had been in that quarter for ten 
days. It was about noon when we made our expe- 
riments ; the barometer at 30, and Fahrenheit’s ther- 
mometer at 32. 
The (lockings above-mentioned were wove of 
carded and fpun filk, and were more fubftantial and 
weighty, than thofe with which he had made the ex- 
periments mentioned in his third paper. One pair 
was of a deep black, having been twice dyed, in 
order to improve the colour. Another pair was of 
the natural colour of the filk, of a du(ky white j and 
both new. The pair of black weighed four ounces, 
eight pennyweight, and four grains ; and the white 
three ounces, eighteen pennyweight, and fifteen 
grains. 
We began with making a few experiments with 
the thin (lockings formerly made ufe of ; and found 
the refult to be much the fame with what is related 
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