r 503 ] 
other part intituled <c Opinions and conjectures con- 
C£ cerning the properties and effects of the electrical 
<c matter arifing from experiments and obfervations.” 
The four letters, the lad of which contains a new 
hypothecs for explaining the feveral phenomena 
of thunder^ guffs, have either in the whole or in part 
been before communicated to the Royal Society. It 
remains therefore, that I now only lay before the 
Society an account of the latter part of this treatife, 
as well as that of a letter intended to be added 
thereto by the author, but which arrived too late 
for publication with it, and was therefore communi- 
cated to the Society by our worthy brother Mr. Peter 
Collinfon. 
This ingenious author, from a great variety of 
curious and well-adapted experiments, is of opinion, 
that the electrical matter confiffs of particles ex- 
tremely fubtil ; fince it can permeate common mat- 
ter, even the denfeff metals, with fuch eafe and free- 
dom, as not to receive any perceptible ref dance : and 
that if any one fhould doubt, whether the eleCtrical 
matter paffes through the fubftance of bodies, or only 
over and along their furfaces, a Ihock from an electri- 
fied large glafs jar, taken through his own body, will 
probably convince him. 
EleCtrical matter, according to our author, differs 
from common matter in this, that the parts of the 
latter mutually attraCt, and thofe of the former mu- 
tually repel, each other ; hence the divergency in 
a ftream of electrified effluvia § : but that, tho’ the 
C c 2 particles 
§ As the electric ftream is obferved to diverge very little, when 
the experiment is made in vacuo , this appearance is more owing 
to 
