[ 8 92 3 
p. 86—89, Experiments in artificial electricity with lamp-black and oil, p. 89 — 91 
The thick fcum from the furfacc of Linfeed-oil, a very flrong negative electric, 
p. 97. «. 
Oi .'•colours, ele&rical experiments on fome, p. 394, 395;. 
Oil faint, over any fubftance, will defend it from a flight ele&rical fhock, p. 394^ 
393- 
Qli<ve-oil, melted with chocolate, will reflore its electricity, p. 95, 
P 
Paint . Oil paint over any fubftance will defend it from a flight ele&rical fhock 
P- 394> 395- 
Painters. The old painters never gave that brightnefs to the eyes which the moderns 
do in their portraits, p. 35. The former came nearer to nature than the latter, 
ibid. 
Paper , painted with different oil-colours, eleClrical experiments on it, p. 394, 393. A 
coated phial may be charged with electrical fparks from a piece of paper, fuffciently 
to Dierce a hole through a card with its difcharge, p. 396. 
Paris and Greenwich, concerning their difference of longitudes, refulting from the 
eclipfes of Jupiter’s fatellites, obferved during the lalt ten years ; w-ith a comparative 
table of the correfponding observations of the firfl fatellite, made in the principal ob- 
fervatories ; p. 162 — 186. 
Pear-gage , defcription of Mr. Smeaton’s, p. 614 — 616. Quantity of permanent air re- 
maining in the receiver of an air-pump when exhaufted as much as pofflble, can be 
known only by this gage, p. 630, 637. The only means alfo of difcovering what 
part of the receiver contains vapour, and what part permanent air, p. 637. 
Pendulum. Computation of the lerieS which expreftes the time of the defcent of a pen- 
dulum through the arch of a circle, p. 213 — 230. A pendulum-rod of folid glafs 
dilates much lefs than one of fleel, p. 698, 699. 
Perfins who could not diflinguifn colours; an account of three brothers, p. 260. See 
Colours . 
Peter's Rock, a volcanic hill near Invernefs ; an account of it, p. 38^5 — 387. 
Peru , no rain ever in that kingdom, p. 257, Its atmofphere during part of the year 
conftantly obfcured with vapours, and the whole country involved in thick fogs, 
p. 257, 258. Computations of Mr. Bouguers barometrical obfervations in Peru, 
p. 787. 
Phial. A coated phial may be charged with ele&vical fparks fufficiently to pierce 
a hole through a card with its difcharge, from a piece of new flannel, a hare’s fkin, 
or a piece of paper, p. 396. An elettrical experiment on a phia*, the inflde coating 
of which was ftutk with varnilh, p. 398, 399. 
Philofopbical inquiries; concerning them, p. 398, 399. 
i P ipe 
