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ELECTRICS what bodies fo called, 12. fixed in inflammable bodies, alfo in amber, glafs, &c. and efpecially in common air, 204. changed to nonelectrics, 209. per fe, when excited, the æther efcapes to the rubbed electric, proved by Mr. Rackstrow's fulphur globe, 249. per fe, the æther firmly fixed in, 264. non, what, 202, 205. EXPERIMENTS, Dr. Franklin's, 64. The Rev. Mr. Jones', 68. to prove the electrical æther paffes through the pores of denfe bodies, 76, 77, 106. with a glafs tube filled with water, 108. to prove the expanfive property of elaftic fluids, by means of which they mutually repel, 116, & feq. to prove that the primary and fecondary air repel each other, 120. with Mr. Martin's curvated tube, 168. Mr. Haukefbee's, to prove that æther pervades glafs when the air is removed, 127. with a double receiver, 129. a remarkable one, 131. by the common pump to prove the elasticity and fubtilty of the common air, 135. prove a pneuma or a more fubtile active medium than the electrical, made with a downy feather, 148. to fhew how the rarity and elasticity of the electric effluvia are increased in a bladder by heat, or in an exhaufted receiver, 152. to prove the existence and conftant defcent of the pneuma from the upper regions, 158, 159, 161. electrical, to prove the pneuma and magnetic virtue to be one and the fame principle, 164. to prove the visible appearance of the pneuma, 165. of Mr. Haukesbee, to prove it, 170. with thiftle-down to prove the extreme rarity and elasticity of the pneuma, 176. vibrating, 177. to prove æther to be furnifhed from the pores of the inftrument of friction at the glafs, and fupplied from the earth, and its propen

to

propenfity to return to it again, 195. with a pair of fcales, 291. with a pasteboard tube and fcales a representation of electrified clouds, 292. with Mr. Franklin's kite, 296. with M. de Romas" kite, 297. the Leyden one, to fhew the neceffity of forming a circuit, 306. electrical, fhewing the ufe of pointed bodies for the preservation of high buildings, fhips &c. from the effects of lightning, 290, & feq. FIRE, electrical, the fame with lightning, 221, 296. , obtained chiefly from the earth, 226. elementary, invifible in its natural ftate, .233. heat and light not effential properties of, ibid. electrical, retained for 36 hours by the condensing phial, 246. Dr. Franklin's method of drawing it from the clouds by means of an artificial kite, 295. FRANKLIN, (Dr.) his experiments with his magical picture, 65. ,with his electrical jack, ib. --which in

with his felf moving wheel, ib. verted the poles of the needle, ib. his accident, 66. his experiment with his pasteboard tube, with his artificial kite,

295.

9.

II.

1

291. GLASS, one of the strongest electrics per fe, GRAY, (Mr. Stephen) made great improvements in electricity, HALES, (Dr.) his method of producing artificial air, 90. imagined the elements to be of a very mutable nature, 91. HAUKESBEE, (Mr.) the first modern improver of Electricity, 10. his experiments to prove that æther pervades glafs when the air is removed, 126, & feq. with a double receiver, 129. , a remarkable one, 131. his opinion that the electric matter was emitted from the internal subftance of the glafs,

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193.

Ноок,

Hook, (Dr.) his opinion of air.

29.

IMPULSE, begins where attraction ends: Qu. why?

INTUMESCENCE, what,

JONES, (Rev. Mr.) experiments by,
LIGHT, communicated by æther, 142.
in the velocity of, and found,

0.181.

112.
68.

difference
143, & feq.
221, 292.
the ufe of

LIGHTNING, the fame as electrical fire,
obtained chiefly from the earth, 227.
pointed bodies to preferve high buildings, fhips,
&c. from the direful effects of,

290, 292.

MARTIN, (Mr.) his experiments with the curva-
ted tube,

MOPSTICK: diftich on a dried one,"

168.

210.

268.

139.

MUSCHENBROEK, (Mr.) his accidental discovery of
the existence of æther, 154, 245. his method of
charging glass bodies,
NATURE, the most exact proportion obferved in the
operations of, fpecified in the regular motions of
the planets,
283, & feq.
NEWTON, (Sir Isaac) his rules of reafoning in phi-
lofophy, 49. his opinion of a fubtile fpirit or
medium in the pores of grofs bodies, 60, 70, 75.
his opinion of the natural or effential properties
of æther,
PHILOSOPHY, the beft fyftem of, erroneous, why?
285. proceeded on falfe principles, ibid.
PNEUMA, more fubtile and active than the electri-
cal fluid itself, 157, & feq. and 164. in grols
bodies, Lord Bacon's opinion of, 154. constant-
ly defcending from the upper regions, 161. not
the fame as is obtained in common electrical ex-
periments, 163. and magnetic virtue, the fpirit
of æther, 164. the cause of magnetism.ibid.
the visible appearance of, 165. proved by Mr.
Haukefbee,

Haukefbee, 170. the Author's attempt to folve
the phænomena of, 175. extreme rarity and
elafticity of, proved by experiment with thistle-
down,
RICHMANN, (Professor) account of the death of, 319.
ROMAS, (M. de) his experiment with an artificial kite,

176.

297. violent explosions from his tin tube, and
the fire feen 8 or 9 inches long and 5 lines dia-
meter, 313, and 315. the ground perforated
under the tin tube an inch deep and half an inch
wide,
316.
SOUND, conveyed thro' the pores of denfe bodies, 94.
propagated (according to Mr Clare,) thro' bodies
by the vibrations of their folid parts, 95, perfon
born deaf, made fenfible of, 96. feamen's method
of difcovering a leak in a fhip by, 98. propa-
gated thro' folid timber, 99. communicated by
the earth, ib. convey'd by pipes, ib. propaga-
ted (according to the Author) by vibrations of the
elaftic fluid contained in their pores, 101. fmooth
furfaces neceffary to convey, 104. the voice of a
man heard 10 or 12 miles, inftanced by the
watch-word at old Gibraltar, 105.
air the pro-
per vehicle of, 122, and 142. difference in the
velocity of, and light,
143,
SUBTILE SPIRIT, Sir Ifaac Newton's opinion of the,
ર
or MEDIUM, in the pores of gross bodies, 75-
electrical experiments to prove it,
76.
WAREHAM, great bodies of fire feen at, in the great
hurricane,
336.
WATER, in a common dense state, fully faturated
with the electrical fluid, 228. when rarified into
vapour, has lefs than its natural quantity of the
electrical fluid,
230,
WORCESTER, unhappy accident at, by gunpowder,

236. the report heard at 8 or 9-miles distance
from, 237. the glafs of the windows forced in-
wards at the back part of the house, and why?
239.

SECOND PAR T

Æ

THER, confider'd as elementary fire, 1.
the profound abyfs or immenfe void, replete
with the denfeft, 139. the gradual increase
of the denfity of, from the fun, the mechanical
cause why the planets placed at the greateft dif-
tance move flowest,
143.
ATTRITION, of the parts of fire produce and in-
crease heat, 85, and 88. proved by blowing cold
air upon a red-hot iron, 89, 90. of the cold air,
fufes a red-hot iron,

91.

33, 34.

61.

104.

BACON, (Lord) his opinion of fire,
BERKELEY, (Bishop) his account of fire,
BOERHAAVE, (Dr.) his opinion of fire, 45. his
distinction between elementary and culinary fire,
76. his mistake of the caufe of the intense heat
at the focus,
COLD, a privation of heat, 158. and heat, relative
with refpect to our fenfations, ib. the greatest
degree of, in water, 160. the greatest degree of,
neceffary to convert quickfilver into a folid, 161.
COR MUNDI, fimilar in its office to the heart in the
body,

133.

DATA, proper, as neceffary in Philofophy, as in
Mathematics,

EARTH, diameter of the,

128.

124.

ELECTRICAL FLUID, denied by fome to be fire,

with their reafons,

11, 12.