[ 419 ] 
other experiments, made with the fame intent. 
I then procured a circular piece of coloured box, 
which was glued to the top of the it and to my 
prime-conduCtor ; when, drawing ftrong fparks 
through this •wood (of whatever colour it was), I 
became clearly of opinion, thit the colour of the 
/park varied according to its depth in the weed ; viz. 
if it pafled upon the furface, it was white ; a 
dittle below it, yellow, or orange; jftill lower, 
fcarlet ; and, deeper in the w^ooo, crimfon. 
It having been mentioned, by fome gentlemen, 
as their opinion, that the matter of light, and the 
eleCtric matter, were the fame things ; I made . 
the following experiment, in order to determine 
whether there was any foundation for fuch an 
opinion or not. 
EXPERIMENT XI. 
I infulated the rubber of my machine, and placed 
it in fuch a fituation, that the rays of the fun, 
paffing through the open window of my room, 
might fall immediately upon it ; but this I obferevd 
produced no electricity. I then collected the rays 
into a focus , by means of a good convex glafs, and 
threw them upon the back of the rubber, till it 
was burned quite black ; but this method was at- 
tended with no better fuccefs. I then mounted 
one of Mr. canton’s electrometers, furnilhed 
with very light balls, upon a Hand of fealing- 
wax ; and, having eleCtrified them negatively, by 
excited amber, fo as to diverge a full inch, I again 
(«) Qpery, If this were really the cafe, fhould not ele&rical 
experiments fucceed, in the moft perfect manner, in the clearejl 
light of the fun ? and would not the evening, or night, be an 
exceedingly improper time to attempt making them ? 
H h h 2 collected 
