Eclipses, the cause of explained, I. 281–288. Annu-
lar, I. 286. Total of the sun, very rare, I. 287.
Account of one seen in Portugal, 287. Supposed
to be omens of calamity, I. 288.

Ecliptic, the earth's annual path round the heavens.
How described, I. 179. How to trace the I. 181.
-183.

Effluvia, fine particles that fly off from various bodies.
Eggs, discoloration of silver with eating, III. 363.
How explained, III. 364.

Elasticity, the quality in some bodies, by which
they recover their former positions after being
bent. What meant by, I. 37.

Electric, what meant by, III. 214. Light, by whom
first seen, III. 214.

Electricity, history of, III. 211. Attractrion electrical,
when first noticed, III. 213. Atmospheric, III. 210.
The two kinds, III. 243. Medical, III. 324. Ani-
mal, III. 330.

Electrometer, Lane's, III. 270. Quadrant, the use of,
III. 273. Another kind, III. 298.
Eolian Harp, structure of explained.

Ephemeris, an almanack. White's explained, I. 185.
Equator, how described, I. 180 and 213.

Equinoctial, what meant by, I. 213.

"Evenings at Home," referred to, a work of great
merit, I. 12.

Eye, the part of which composed, III. 114.

F.

Feathers, electrified, their appearance, III. 247.
Fire Engines described, and the principle of them
explained, II. 190.

Fish, how they swim, II. 201. Air-vessel of, the uses,
II. 204. Electrical, III. 256. .

Flannel, a conductor of sound, II. 276.

Flea, circulation of the blood of a, I. 25.

Flood-gates, why made very thick, II. 78.

Fluids and solids, how distinguished, II. 36-38. Par-
ticles of exceedingly small, II. 15. Incapable of
compression, II. 18, 19.

Fluids press equally in all directions, II. 26. Incom-
pressible, II. 29. Air, compression of. ib. Weight
and pressure of, experiments on, II. 32-35. La-
teral pressure of, II. 41--47. Difference between the
weight and pressure of, II. 73. Motion of, II. 74--91.
Experiments on the light and heavy, II. 138-141.
Specific gravity of, differ according to the degrees
of heat and cold, II. 145.

Force, centrifugal, what meant by, I. 88.
Fountains, the principle of, explained, II. 86.
Fountain, artificial, II. 258.

Franklin, Dr. his experiments, III. 301. discovers
that lightning and electricity are the same, III.
302.

Friction, rubbing. Must be allowed for in mechanics,
I. 136.

Frogs, experiments on, III. 212–217.

Fulcrum, the prop or centre on which a lever turns.
What meant by, I. 107.

G.

Galvani, Dr. his discoveries, III. 347, 348. Experi-
ments on frogs, ib. and 370.

Galvanic batteries, how formed, III.356--358. Shock,
III. 357-359.

Galvanism, what it is, III. 348. From what it derived
its name, ib. And electricity the same, III. 351.
Made apparent to the senses, III. 352. Positive
and negative, III. 366. Summary of, III. 377.
Garden engines, described. II. 191.

Gas, a kind of air. Hydrogen, how procured. III.000.
How collected, ib.

Gauge, a measure.

Geocentric place of a planet, what meant by, I. 322.
longitude, I. 323.

Globe, the greater part of its surface water, II. 317.
A representation of the earth, I. 211.
Glue, for what used, I. 34.

Gravity, the tendency which bodies have to the
centre of the earth. Centre of, what meant by,
1. 64. How found, I. 65. Acts upon all bodies,
I. 41. The law of, I. 42. and 50. Illustrated, III.
42-44, and 50-52.

Gravitation, attraction of, defined, I. 39. Instances
of, I. 39. By this force bodies tend to the centre
of the earth, I. 41.

Gregory, Pope, rectifies the Julian year, I. 268.
Guinea, specific gravity of, II. 107.

Gunpowder, how fired, III. 360.

Gymnotus, described, III. 333.

H.

Hammer, philosophical, II. 115.
Hampstead, the fine prospect from, III. 126.
Harvest moon, explained, I. 297-305. Cause of,
I. 299.

Heat, expands all bodies, I. 29. The cause of great,
I. 244.

Height of any place how found, I. 57, 58.

Heliocentric longitude, I. 322.

Herschel, the planet when discovered, I. 332. Its
magnitude, distance, &c. I. 333-335.

Hiero's crown, cheat respecting, how detected, m.
126-128.

Hogshead, how burst, II. 63.

Hop-waggons, dangerous to meet in an inclining road,
I. 70.

Horizon, the boundary where the sky seems to
touch the surface of the earth or sea. Sensible
and rational, I. 225. To which we refer the rising
and setting of the sun, I. 226.

Hydraulics, hydrostatic principles applied to mills,
engines, pumps, &c.

Hydrometer, an instrument to measure the strength
of spirits. Described, II. 142–145. To what ap-
plied, II. 147.

Hydrostatics, the origin of the term, II. 11. The
objects of, II. 12.

Hydrostatical paradox, explained, II. 48–57.

Hydrostatical bellows, described, and explained, II.
58-65. Press, II. 65, and 193-195.

Fluids,
pressure of in proportion to the perpendicular
heights, II. 59.

Hygrometer, an instrument by which the moisture
of the air is measured. Its construction and use,
II. 388. Different kinds of, II. 388-393.

I.

Jack-a-lanthorn, III. 317.

Immerse, to plunge in.

Impel, to drive on.

Incidence, line of, II. 298.

Incompressible, not capable of being pressed into a

smaller compass.

Inertia, of matter, its tendency to continue in the

state in which it is.
Ingenhouz, Dr. referred to, I. 35.

His character

ib.
Interstices, the hollow spaces between the particles
of matter.

Iron, oxide of, III. 353.

Jupiter, the planet, its magnitude; distance from
the sun; the velocity of its motions, I. 324. The
length of its days and nights, I. 325. Satellites,
I. 325.

Julius Cesar, the part he took in reforming the year,
I. 265, 266.

L.

Lateral, sidewise.

Latitude, of the planets, their distance from the
ecliptic. Parallels of, I. 242.

Lead, eleven times heavier than water, II. 45. Ox-
ide of. III. 352. Acetite of, III. 368.

Leaf, gold, silver, &c. how burnt, III. 360.
Leaks, in banks, how secured, II. 80.

Leap-year, what meant by, I. 265. Rule for knowing,
I. 267.

Lenses, different kinds described, III. 45.

Levels, construction of, II. 24. Use of, II. 24, 25.
Lever, a bar, crow, &c. For what used, I. 108. Why
called a mechanical power, I. 109. Of the first
kind, what instruments referred to, I. 117. How
to estimate its power, I. 118. Of the second,
kind, what instruments referred to, I. 118. Of
the third kind, what instruments referred, to, I.
120-122.