C 3°9 ] 
I cannot enter into this particular fubjeCt, without 
firffc fettling a difpute amongft electricians, which fub- 
fifts at this day, concerning the two electricities ; be- 
caufe fome confequences, drawn from the feveral ex- 
periments I have to produce, greatly depend upon it. 
Polifhed glafs, upon being rubbed properly, has 
been fuppofed to give an electricity to bodies, and 
thofe bodies that receive it from the glafs, are faid to 
be eledtrified phis. Whereas wax, amber, &c. upon 
being rubbed in the fame manner, have on the con- 
trary been fuppofed to receive an electricity from 
bodies, and thofe bodies which part with it are faid 
to be electrified minus. But no experiment, that I 
know of, has yet appeared to determine which of 
thefe electricities does really eleCtrify plus, and which 
of them does really eleCtrify minus • though it hap- 
pens that the faCt turns out juft as they have all along 
fuppofed* 
In a fecond treatife upon the fubjeCt of electricity, 
that I publifhed in the year 1748, feveral experi- 
ments were produced, to fhew that all bodies are fur- 
rounded with a medium , which is of an exceedi?jg 
elajlic nature , and extends but to a very (mall dif- 
tance from the body when it is not difturbed by heat, - 
or other caules. Since that, other experiments of the 
like kind have been publifhed in a work, wherein 
my late worthy friend Dr. Hoadly was concerned 
with me. Among the proofs therein given, is a cu- 
rious one, which I obferved in the ‘Torricellian va- 
cuum. , where the appearance was remarkably fenfible. 
And what is more lingular, that fame appearance not 
only proves the exigence of a medium, at or on the fur- 
face of bodies, but at the fame time determines which 
