C 84 ] 
very fail on that day. But mod: undoubtedly the 
drong rapid tide of the Severn mud have been af- 
fected in a very remarkable manner, had there been 
any curious perfons to take notice of it. 
XIII. A Letter containing fome Experiments 
in Electricity, to Mr . Benjamin Wilfon, 
F. R. S. from Mr, Torbern Bergman, of 
Upfal, in Sweden. 
Amplidime atque celeberrime domine. 
Read Feb. z 3, I y Xperimentorum circa corporum ad- 
1 j fridtum jam ea funt commemoran- 
da, quae cum ferico inditui 5 cujus vis ele&rica, etfi a 
domino Gray dudum inventa, tamen hucufque parum 
fuit explorata. Pulchra funt quae adtulit dominus 
Symmer ; fed non fufficientia. Ne vero longa narra- 
tione variorum tentaminum charta impleatur ; palma- 
ria tantum, et e quibus reliqua intelligi podunt, adfe- 
ram. Nova ligamenta fericea, unum- circiter polli- 
cem geometricum Suecanum lata, adhibui. Alterum 
extremitatibus fixum et bene tenfum, quod in pof- 
terum fricatum voco, alterum vero feu fricans mani- 
bus, quantum fatis, expando, fuper eodem fpatio 
fricati pluries duco reducoque perpendiculariter ad 
ejus longitudinem. Hanc operationem tranjverjant 
adpello : earn vero qua idem fpatium fricantis ducitur 
antrorfum retrorfumque, fuper tota longitudine fricati, 
Jecimdum longitudinem fieri dico. 
5 
Si 
