[ 773 3 
of which I gave an account in my treatife de aver - 
terufi fulminis artijicio , page 10 and n. Having 
drawn thefe feeds together on a heap upon the plate, 
I brought over them the fphere of metal, the fize 
of which is arbitrary, impregnated with this elec- 
tricity. Upon bringing this fphere near the plate, 
the electricity exploded, by which the feeds were fet 
all on fire. Thefe feeds were dry, and had no in- 
flammable fpirit mixed with them. The flame 
which arofe from thefe feeds is true fire, as it lighted 
fome flax, which lay upon the feeds, and ex- 
tended itfelf beyond the metal. 
On the 13th of January I put fome aurum fill - 
minam upon a circular piece of parchment : this 
parchment I cemented to a plate of metal, and caufed 
the bottle replete with eledricity to be difcharged 
thereupon. Immediately the aurum fulminam ex- 
ploded with a very loud report, and the circle of 
parchment was torn all to pieces. 
XCI. An Account of a Fire-Ball , feen at 
Hornfey, by William Hirft, F. R. S. com- 
municated in a Letter to Samuel Mead, 
Efq\ F. R. S. 
S I R, Hornfey, April 6, 1754. 
Read May 30, T ~T A D not illnefs prevented, I fhould 
1 754- £ I have troubled you fooner with an 
account of a phenomenon, which I happened to fee 
on the 26th of February lafl, about five minutes be- 
fore eleven at night. 
I -was 
