of their motions, i. 145. How to find their dis-
tances, i. 226, 227.

Pneumatics, what, treated of under, ii. 137.
Points, cardinal, i. 124.

Pole-star, its use, i. 124.

Poles, apparently stationary, i. 165. At the, only
one day and one night in the year, i. 182.
Press, hydrostatical, ii. 45, 46.

Priestley, Dr. his history of electricity referred to,
iii. 150.

Price, Dr. referred to, i. 40.

Prism, the effect of, iii. 95.

Puddling, what meant by the term, ii. 57.
Pulley, how explained, i. 96. The single gives no
advantage, ib. The moveable, i. 98.

Pump, principle of, ii. 123-128.

Pump, forcing, described, ii. 128.

Pyrometer, its construction and use, ii. 260.

R

Radiant-points, from whence rays of light flow in

all directions.

Rainbow, the cause explained, iii. 94.

Artificial,

iii. 99. Curious ones described, iii. 99, &c.
Rain-gauge, its construction, ii. 266. How it is
used, ii. 267.

Rain, an electrical phenomenon, iii. 222.

Rays, pencil of, what meant by, iii. 32. Parallel,
definition of, ib.

Reflection, rebounding back. Its powers in appa-
rently multiplying objects, i. 121. Line of, ex-
plained, ii. 202.

Refraction, inclining or bending out of its course.
Its power in apparently multiplying objects, i.

122.

Repulsion, driving away. What meant by, i. 27.
Instances of, i. 27, 28.

Residuum, electrical, what meant by, iii. 188.
Retrograde motion, by which the heavenly bodies
appear to go backwards.

Reverberate, to beat back.

River, New, how it supplies London with water,
ii. 63. Reservoirs belonging to, ii. 64.
Rivers, banks of, must be very thick, ii. 57.
Round-abouts, the principle of, i. 75.

S

Saliva, decomposed by Galvanism, iii. 244.
Salt, whatever has a sharp taste, and is soluble in

water.

Salt water, heavier than fresh, consequence of, to
a loaded vessel, ii. 104.

Satellites, moons.

Saturn, the planet, how known, i 234. Its magni-
tude, distance from the sun; the velocity of its
motions, i. 234, 235. Its satellites and rings, i.
235. The length of its day and night, i. 236.
Screw, an inclined plane wrapt round a cylinder.
Its principle explained, i. 107. Of what com-
posed, i. 108. Examples of, i. 109. Used by
paper-makers, i. 112. Its power estimated, ib.
Season, the hottest, i. 178.

Seasons, variety of, on what depends, i. 171, 176.
Different, how accounted for, i. 171, and 183.
How produced, i. 178.

Ship, damaged by lightning, iii. 216.
Silurus electricus, described, iii. 231.
Silver, experiment with, iii. 243.

Siphon, the structure of, explained, ii. 108. Its
principle, ii. 110.

Slaves, how they get at their master's rum, ii. 99.
Smoke, the reason of its ascent, ii. 181.
Smoke-Jack, its principle, ii. 213.

Solar System, described, i. 142, 148.
Solder, for what used, i. 26.

Sound, conductors of, ii. 187, 188. How far may
be heard, ii. 191. How fast it travels, ii. 193.
Velocity of, applied to practical purposes, ii. 194,

195.

Spark, electrical, its nature, iii. 199. Galvanic, its
power, iii. 256.

Specific gravity, what meant by, ii. 26. Of bodies
explained and illustrated, ii. 65, 96. How to find,
ii. 67.

Spectacles, their construction, uses, and different
kinds, iii. 90, 94.

Spirit, rectified, what meant by, ii. 101, &c.
Springs, intermitting, explained, ii. 113.

St. Paul's, whispering gallery of, principle explain-
ed, ii. 208.

Stars, how to find the names of, i. 126, 129. Why
marked on the globe with Greek characters, i.
129. Fixed, their apparent motion, i. 165. Why
not seen in the day, i. 166. Fixed, their number,
i. 117, 118. May be distinguished, i. 123. Fixed,

1

their immense distance, i. 185. Fixed, descrip-
tion of, i. 145, 247. Their uses, i. 248. Falling,
what they are, iii. 310.

Steam engine, its use, ii. 221. When invented, ii.
222. Its structure, ii. 224. The application, ii.
231, 232. That of Messrs. Whitbread described,
ii. 233. Its power calculated, ib. Accidents oc-
casioned by, ii. 235.

Steelyard, a sort of lever, i. 82. Its advantages over
a pair of scales, i. 82.

Storms, by what occasioned, ii. 218.

Suction, no such principle in nature, ii. 153–157.
Sulphuret, akaline, what, iii. 253.

Summers, two in a year, in some places, i. 181.
Sun and Clocks, seldom together, i. 140.
Sun, declination of, i. 137. Longitude of, i. 141.
Has not latitude, ib. Its magnitude, i. 143. Why
it appears so small, ib. Its distance from the
earth, i. 144. Annual motion of, how observed,
i. 168. Reasons for, i. 130. Nearer to the earth
in winter than in summer, i. 177. A description
of, i. 243, 244.

Swimming, theory of, ii. 105. How to be attained,
ib. Less natural to man than to other land ani-
mals, ii. 106.

Syringe, its structure explained, ii. 150. Condens-
ing one described, ii. 177.

T

Tables, Galvanic, iii. 253, 254.

Tangent, a straight line, touching the circumference
of a circle in one point.

Tangible, capable of being felt or handled.
Tantalus's cup, ii. 111.

Taste, a disagreeable one, excited by the union of
metals placed on and under the tongue, iii. 243.
How accounted for, iii. 244.

Telescope, refracting, explained, iii. 100. Night,
iii. 151. Reflecting, explained, iii. 107. Dr. Her-
schel's, iii. 110.

Terms, technical, derived from the Greek language,
ii. 9.

Thermometer, its construction and uses, ii. 250-
254. Its scale, ii. 254. Wedgewood's, ii. 256.
Reaumur's scale compared with Fahrenheit's,
ii. 259. Heat, scale of, ii. 258.
Thunder, how produced, ii. 189.

Tides, the causes of, explained, i. 207-212. Two
every 25 hours, i. 210. Different in different
places, i. 211. When the highest happen, i. 212.
Time, equal and apparent, how distinguished, i.
183, 184.
On what the difference dépends, i.
184. Equation of, i. 140 and 183-189. Divi-
sion of, i. 194.

Time and space, clear ideas of, necessary to be
formed i. 75.

Torpedo, described, iii. 228.

Torricellian, experiment, ii. 148.

Transferrer, an instrument used in pneumatics.
Transit of Venus, her passage over the sun's face.
Trembling eel, noticed, iii. 232.

Triangle, what meant by, i. 13. Any two sides of,
greater than the third, i. 68.

Tropics, circles parallel to the equator.