A piece of zinc may be kept in water a long time, without scarcely oxidating at all; but the oxidation takes place very soon if a piece of silver touch the zinc, while standing in the water.

If a cup made of zinc or tin be filled with water, and placed upon a silver waiter, and the tip of the tongue be applied to the water, it is found to be insipid; but if the waiter be held in the hand, which is well moistened with water, and the tongue applied as before, an acid taste will be perceived.

Charles. Is that owing to the circuit being made complete by the wet hand?

:

Tutor. It is another experiment of a similar kind as the following: If a tin bason be filled with soap-suds, lime-water, or a strong ley, and then the bason be held in both hands, moistened with pure water, while the tongue is applied to the fluid in the basan, an acid taste will be sensibly perceived, though the liquor is alkaline.

From this short account of Voltaism, it may be inferred :—

(1.) That it appears to be only another mode of exciting electricity.

(2.) Voltaic electricity is produced by the chemical action of bodies upon each other.

(3.) The oxidation of metals appears to produce it in great quantities.

(4.) Voltaic electricity can be made to set inflammable substances on fire, to oxidate and even inflamne metals.

(5.) The nerves of animals appear to be most easily affected by it of any known substances.

(6.) Voltaic electricity is conducted by the same substances as common electricity. (7.) When it is made to pass through an animal, it produces a sensation resembling the electrical shock.

(8.) The electricity produced by the torpedo and electrical eel, is very similar to Voltaism.

INDEX AND GLOSSARY.

TO THE

THREE VOLUMES.

ABSORB, to drink in.

A.

Accelleration, a body moving faster and faster.
Action and re-action, equal and contrary, vol. I. p. 96.
Curious instance of, I. 98.

Adhesion, a sticking together.

Air, a fluid, the pressure of which is very great II.
199, 200. Its pressure, experiments on, II. 222-
235. Its weight, how proved, II. 236. Its elasti-
city, II. 244-249. Its compression, II. 255–262.
Necessary to sound. II. 273.

Air-gun, structure of, explained, II. 269, 270.
Air-pump described, II. 206. Its structure explained,
II. 207-210. Experiments on, II 212 and 263.
Alcohol, ardent spirit: equal parts of alcohol and wa-
ter make spirits of wine.
Alkaline, a saline taste.

Anamorphoses, distorted images of bodies.

Ancients, their mode of describing the constellations,
II. 170.

Angle, what it is, I. 14. How explained, ib. Right,
obtuse, acute, ib. How called, 15.

Animals, all kinds of, affected by Galvanism, III.

218.

Aperture, a small hole.

Aphelion, the greatest distance of a planet from the

sun.

Apogee, the sun's or moon's greatest distance from
the earth.

Aquafortis, of what composed, I. 20.

Archimedes proposed to move the earth, I. 104. Some
account of II. 123. His inventions, II. 124.

Arrow, to find the height to which ascends, I. 61,62.
Atmosphere, the effect of, III. 42, 43.

Attraction, the tendency which some parts of matter
have to unite with others.

Attraction capillary, what meant by, I. 32. Illustra-
ted, 1. 33.

Attraction and Repulsion, electrical, III. 217 and 242.
-,magnetic, III. 189, &c.
Aurora Borealis, vulgarly called the Northern lights.
Its use in the Northern parts of the globe, I. 304.
Imitated, III. 313. A curious one described, III.
315.

B.

Balance, hydrostatical, described, II. 106.
Balances, false, how detected, I. 115.

Ball, why easily rolled, I. 67. Scioptric, its effect,

III. 61.

Barometer explained, II. 238 and 361-368. Its con-
struction, II. 351. Its use, 352. Standard altitude
of, II. 355. Variation of, ib. To measure altitudes
with, II. 361.