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-Galvanometer, 48, 26.-Galvanic Circuits, 50, 510.-Grove's
Battery, 53, 336.--Galvanic Reduction of Brass, 62, 230–Galvanic

and Electro-magnetic Experiments, 68, 161, 181, 188 and 207. Joule. Electric Origin of the Heat of Combustion. Phil. Mag. J. 20,

98; 22, 204.-Electrolysis, 24, 106. Knochenhauer. Experiments on Combined Electricity. Pogg. 58, 31. Köhler. Thermo-electricity. Pogg. 17, 146. Kolbe. Electrolysis of Valerianic Acid. Phil. Mag. J. 31, 348. Lenz. Peltier’s Experiment. Pogg. 44, 342.- Conduction, 45, 105.

Development of Heat by Galvanic Action. Pogg. 61, 18. Lenz & Schwelger. Galvanic Polarization, and Electromotive Power of

Hydro-circuits. Pogg. 67, 497; also N. Ann. Chim. Phys. 20, 183. Marianini. Bibl. univ. 42, 87_(also Schw. 58, 429); 47, 253.--Ann.

Chim. Phys. 33, 113 (also Pogg. 8, 165; also Schw. 49, 22, 264 and 452); 38, 5 and 337; 42, 531 (also Schw. 51, 177); 45, 28 and 113;

51, 130. Martens. Chemical Action of Galvanic Currents. Pogg. 58, 234.

Passivity of Iron, 61, 121.
Matteucci. Schw. 57, 67; 59, 369.--Ann. Chim. Phys. 43, 256 (also

Schw. 60, 305); 58, 75; 66, 225; 71, 90; 74, 99 and 105.-Electro-
Physiology. Phil. Mag. J. 26, 175.-New Experiment on Static
Electric Induction, 26, 320.- Animal Electricity, 26, 534.-Deve-
lopment of Electricity by Chemical Action, N. Ann. Chim. Phys.

16, 257.-Electrical Fishes, 21, 160.
Mohr. Galvanism. Pogg. 39, 129; 42, 76; 51, 372 and 376.
Mullins. Galvanic Apparatus. Phil. Mag. J. 9, 283; 10, 281; 15, 37.
Münke. Electricity of Vapour of Water at Low Temperatures. Pogg.

67, 376. Munk af Rosenchöld. Galvanism. Pogg. 35, 46; 43, 193 and 440. Napier. Electrical Endosmose. Phil. Mag, J. 29, 10.-Electrolysis.

29, 92. Nobili. Rings. Pogg. 10, 392 and 405. Bibl. univ. 36, 3; 37, 177;

also Schw. 53, 441 and 456.-Motions of Mercury. Bibl. univ. 35, 261; also Schw. 54, 40.—Galvanism. Bibl. univ. 37, 10; also Pogg. 14, 157.-Nature of Electrical Currents. Bibl. univ. 37, 118; also

Schw. 53, 264, Oerstedt. Electro-magnetism. Schw. 29, 275; also Gilb. 66, 291.-Cir

cuit of two Elements. Schw. 33, 163. Ohm. Laws of the Electric Current in a Galvanic Circuit. Pogg. 6,

459; 7, 45 and 117. Schw. 58, 393.—Unipolar Conductors. Schw. 59, 385.—Galvanic Circuit. Schw. 63, 1, 158 and 385; 64, 20, 138

and 257. Parrot. Chemical Electricity. Gilb. 61, 88; Ann. Chim. Phys. 42, 45;

46, 361. Peclet. Contact-electricity. Ann. Chim. Phys. 77, 233. Peltier. Heat and Cold developed by the Electric Current. Ann. Chim.

Phys. 56, 371; also Pogg. 43, 324.—Statical and Dynamical Elec

tricity. Ann. Chim. Phys. 67, 422. Pfaff. Galvanism. N. Gehl. 5, 82; Schw. 48, 190; 53, 77 and 395; 55,

258; 64, 1. Pogg. 40, 443; 44, 512; 49, 461; 51, 110 and 210;

53, 20, 203 and 313. Poggendorff. Galvanism. Pogg. 49, 31; 50, 255 and 264; 52, 497;

53, 343 and 436.-Hydro-electric Currents of the higher Orders. Pogg. 61, 408.-Conduction of Galvanic Currents by Liquids. Pogg. 64, 54.- Electro-thermal Decomposition, and two new Eudiometrical

Methods. Pogg. 71, 226.
Pohl. Galvanism. Pogg. 14, 71; 16, 101; 46, 595; 50, 497.
Porret. Galvanic Decomposition. Ann. Phil. 8, 74; also Gilb. 66, 272.
Pouillet. Electricity by Evaporation. Bull. Philomath. 1825, 100.

Ann. Chim. Phys. 36, 4; also Pogg. 11, 442.—Electricity by Com-
bustion. Ann. Chim. Phys. 35, 401; also Pogg. 11, 417.-Law of
Force of the Current in the Voltaic Pile. Compt. rend. 4, 267; also
Pogg. 42, 281.-Thermo-electricity. Compt. rend. 4, 785; also

Pogg. 42, 297.
Riess. Electrical Properties of Burning Bodies. Pogg. 61, 545.—Elec-

trical Condition of certain Bodies, 64, 49. P. Riess & G. Rose. Pyro-electricity of Minerals. Pogg. 59, 353. H. Rose. Metallic Reduction. In Grotthuss' Physico-chemical Re

searches, 139. Schafhäutl. Electricity by Evaporation. Phil. Mag. J. 18, 95. Schönbein. Passive Condition of Iron, Tin, and Bismuth. Phil. Mag. J.

9, 73; Pogg. 37, 392; 38, 404 and 492; 39, 137, 342 and 352; 40, 193; 41, 41; 43, 1 and 17; 51, 390.–Nobili's Rings, 40, 621.Peroxide of Lead, 43, 89.- Chemical Tendencies, 43, 229.-Against the Theory of Contact, 44, 59.--Secondary Currents, 46, 109; 47, 101.- Nitric Acid and Alcohol, 47, 563.—Electrical Odour, 50, 616.-Theory of the Gas Voltaic Battery. Phil. Mag. J. 22, 165.

Ozone, 27, 197. Seebeck. Thermo-electricity. Gilb. 63, 115 and 430. Pogg. 61, 133

and 253. Schweigger. Electricity by Evaporation. Schw. 44, 172; 51, 77.

Galvanism, 52, 33. Simon. Galvanic Decomposition of Salts. N. Tr. 22, 1, 1. Singer. Elements of Electricity and Electro-chemistry. Translated into

German by Müller. Bresl. 1819. Smee. Galvanism and Electro-type. Phil. Mag. J. 16, 315, 422 and

530; 25, 434. Volta. Electricity by Evaporation. Gilb. 5, 39.-Voltaic Pile, 6, 340

and 468.-Fundamental Experiment, 9, 239, 25, 379 and 389; 10, 389 and 409.-Galvanism, 10, 421; 12, 497; 13, 257; 19, 491; 21

133; 51, 341. Wach. Metallic Arborescence. Schw. 58, 20. Walcker. Galvanism. Pogg. 4, 301 and 443; 47, 123. Wartmann. Connection of Light, Heat, and Electricity. Phil. Vag. J.

23, 254. Wetzler. Metallic Reductions. Schw. 49, 470; 50, 88 and 129; 56,

206.-—Iron and Lead. Schw. 54, 333.-One Metal and one Liquid.

Schw. 58, 302. Wheatstone. Description of various new Instruments and Processes for

determining the Constants of a Voltaic Battery. Phil. Trans. 1843,

II, 303; also Pogg. 62, 499. Williams. Electricity by Evaporation. Phil. Mag. J. 18, 93. Wollaston. Chemical Electricity. Phil. Trans. 1801, 427; also Ann.

Chim. Phys. 16, 45. Yelin. Thermo-electricity. Gilb. 73, 661 and 415.- Neue elektromag

netische Versuche. München, 1823. Zamboni. Dry Piles. Gilb. 60, 151.- Pile with two Elements. Gilb.

60, 162.

The term Electricity is applied, according to the dualistic theory of Dufay and Symmer, to two imponderable fluids, very similar in their properties, but diametrically opposed in their mutual relations;—or, according to the theory of Franklin, to a single imponderable fluid, the relative excess or deficiency of which is supposed to produce the phenomena of Positive and Negative Electricity*.

Properties. 1. The two Electricities are imponderable.

2. They diffuse themselves uniformly and with the greatest rapidity through those spaces which they are able to penetrate.

* The dualistic theory is not only better adapted to the chemical view of electrical phenomena, but likewise affords a much more satisfactory explanation of the distribution of electricity. For how is it possible, on the Franklinian hypothesis, to form a clear conception of the manner in which a body deficient in electricity, and placed in the neighbourhood of another containing electricity in excess, exhibits a still greater deficiency on the side nearest to the latter, and an excess on the opposite side (a)? The approximation of a hot and a cold body does not appear to be accompanied by any phenomena, resembling the distribution of electricity. The experiment of Moll (p. 315) is also favourable to the dualistic theory.

1(a). The Franklinian theory is perfectly competent to the explanation of this and every other phenomenon of statical electricity. The fundamental principles of that theory may be stated as follows: I. The particles of the electric fluid repel each other and attract those of ponderable matter. II. The particles of ponderable matter repel each other, and attract those of the electric fluid. III. In the ordinary state of a body, the quantity of electric fluid contained in it is such, that the attractive force exerted by the ponderable matter of the body on a particle of electric fluid situated without, is exactly balanced by the repulsive force exerted by the electric fluid of the body on the same particle. IV. A body containing more than this natural quantity of electric fluid is said to be positively electrified, and a body containing less than its natural quantity is said to be negatively electrified.-Now suppose a body A, negatively electrified, to be brought into the neighbourhood of a body B, positively electrified. The excess of electric fluid in B repels the fluid still remaining in A towards the end farthest from B, thus leaving the nearer end of A more negative than before,--and at the same time the redundant ponderable matter in A attracts the electric fluid in B towards itself, thus rendering the nearer end of B, more positive, and the farther end less positive than before. A similar explanation will apply to every case of statical induction. Indeed it is only necessary to state the two theories in precise terms, in order to see that any phenomenon of statical electricity which is explicable by the one, must of necessity be explicable by the other also, -the redundant matter of the one theory producing, in fact, the same effects as the negative electric fluid of the other. The difference between the two theories is that the one supposes a single and the other a double transfer of electric fluid to take place, in all cases of charge and discharge: but this makes no difference in the ultimate distribution of the positive and negative charge, which is all that we are concerned with in phe. nomena like that just noticed. The author's remarks in the preceding note seem to be based upon the notion that a body negatively electrified is supposed, according to the Franklinian theory, to be absolutely deprived of electric fluid. Such however is not the case, any more than we suppose a cold body to be absolutely deprived of heat. As to the experiment of Moll alluded to in the same place, I will only observe that the perforation of a card or a piece of tinfoil by the electric discharge, by no means obliges us to suppose that the electric fluid or fluids are bodily carried through the perforations. In making these remarks, I would not be understood to advocate the theory of a single electric fluid in preference to the other, -or indeed the existence of an electric fluid at all: my object is merely to point out the perfect similarity of explanation, afforded by the two theories, of all the phenomena of ordinary electricity. [For a full development of the theory of Franklin (or rather of Æpinus) I must refer to Robison's Mechanical Philosophy, Brewster's Edition, vol. IV.; also to the admirable treatise of Dr. Roget in the Library of Useful Knowledge, Natural Philosophy, vol. II. The latter work, pp. 60....64, contains a concise and able comparison of the two theories.] [

To the class of good conductors of Electricity belong the metals, certain metallic sulphurets, both natural and artificial, scale oxide of iron, peroxide of manganese, peroxide of lead, graphite, and charcoal.

Electricity travels along a copper wire faster than light moves in the celestial spaces, and with the same velocity from the positive to the negative end as in the contrary direction. If a copper wire of the length of į an English mile be cut through in the middle, and its extreme ends brought near to the inner and outer coatings of Leyden jar, the spark will appear at the two coatings at the same instant, but somewhat later in the middle. (Wheatstone, Ph. Tr. 1835, ii. 583; also Pogg. 34, 464.) The conducting power of metals deminishes as their temperature rises. (De la Rive.) Solid mercury conducts electricity better than the same metal in the liquid state. (De la Rive.)

Conducting Power of Metals.
Lenz.

H. Davy. Becquerel. Christie. at 0° at 10° at 200° Silver 136.25 94:45 68.72 109

73.6 100 Copper 100.00 73.00 54.82 100

100

66 Gold. 79.79 65.20 54:49

73
93.6

73 Tin 30.84 20:44 14.78

155

17 Brass..

29.33 24.78 21:45 Iron 17.74 10.87 7.00

14.5 15.8

15 Lead 14.62 9.61 6.76

6.9
8.3

8 Platinum 14.16 10.93 9.02

18
16.4

16 Zinc,

28.5

37 Mercury

3.4 Potassium..

1.3 If the conducting power of copper at 19° = 100, that of antimony = 8.87, of mercury 4.66, and of bismuth 2:58. (Lenz.)- According to Pouillet, the conducting powers of platinum, copper, and palladium are as 2.5 : 16 : 30.

If it be assumed that metallic wires of equal thickness will be more strongly heated by the passage of an electric current in proportion as their conducting power is less, the following conducting powers may be deduced from the degrees of heat actually produced: Copper, silver, and alloys of 1 part copper with }, 1 or 3 parts silver, 100;--gold, 66:6—zinc, brass, and alloy of 1 part tin with 8 parts copper, 33:3;—an alloy of 1 part gold and 1 silver, 30;-—an alloy of 1 part gold with 1 silver or } copper, 24;—an alloy of 1 part tin and 1 zinc, 22-2;-platinum and iron, 20;-an alloy of 3 parts tin and 1 zinc, 18.8;—tin, 16:6;—an alloy of 3 parts tin and i lead, 13:3;—an alloy of 1 part tin and i lead, 11•1;-an alloy of 1 part tin and 3 lead, 9:5;-lead, 8-3. (Harris, Phil. Transact. 1827; abstr. Pogg. 12, 279.)

Ignited copper wire condncts better than the same wire unignited; and soft steel better than that which has been hardened. (Peltier.) — The conducting power of a wire of any given metal varies directly as its transverse section and inversely as the square of its length. (Christie.)

Among ores, copper-nickel is the best conductor; then follow purple copper, copper pyrites, and copper-glance, all three of which conduct well; then, -regularly diminishing in power,-iron pyrites, arseuical pyrites, galena, arsenical cobalt, peroxide of manganese, Tennantite and Fahlerz. (R. W. Fox, N. Edinb. J. of Sc. 4, 266.)

The feeble thermo-electric current of a single pair of bismuth and antimony is very well conducted by sulphuret of bismuth, galena, scale oxide of iron, protosulphuret of iron, iron pyrites, arsenical pyrites, copperglance, artificial disulphuret of copper, and purple copper;-moderately well by peroxide of manganese and peroxide of lead;—not sensibly, when the surface of contact is small, by blende, tinstone, protosulphuret of tin, magnetic iron ore, specular iron, wolfram, suboxide of copper solidified after fusion, red oxide of mercury, and cinnabar. It is remarkable that Mn 02 and Pb 02 should conduct electricity so well, seeing that Mn 0 and Pb O do not transmit the current even of a powerful battery. (Faraday.)

Imperfect Conductors or Semi-conductors.

Chalk and other minerals, earthenware, sulphuret of molybdenum, and tin pyrites.

Marekanite conducts electricity well under 19°; less freely at a higher temperature, and not at all at 37.5°: moisture is not the cause of the difference. Similar properties are exhibited by common obsidian, iolite, and many lavas. (P. Erman, Pogg. 25, 657.

Sulphuret of silver, both natural and artificial, and likewise red silver, conduct the electricity of a battery of 20 pairs, feebly when cold, but more and more readily as they become hotter, and at a certain temperature almost as well as a metal: on cooling, their conducting power again decreases. Fluoride of lead solidified and cooled after fusion, does not conduct the current; but when heated to redness it conducts very well, and fuses by the heat which the current excites. (Faraday.)

b. Liquids. Water when pure is a very bad conductor of electricity, but acquires considerable conducting power by dissolving a variety of substances, even such as do not conduct of themselves, e. g., bromine, iodine, chlorine, and sulphurous acid; it likewise converts solid insulators (snch as silk) into semi-conductors by moistening them. (De la Rive.) The conducting power and decomposibility) of water are most highly augmented by phosphoric, sulphuric, nitric, and oxalic acid, potash and soda, carbonate and nitrate of potash, carbonate of soda, many other salts, metallic chlorides and iodides; then follows carbonate of ammonia; then tartaric and citric acid. The following have no influence on the conducting power of water: boracic and acetic acid, ammonia, cyanide of mercury, sugar, and gum. (Faraday.) Under a pressure of 30 atmospheres

, the conducting power of water does not diminish; that of aqueous nitric acid diminishes a little. (Colladon & Sturm.)

Oil of vitriol conducts less easily than dilute sulphuric acid; the maximum of conducting power is possessed by a mixture containing 30 per cent. of anhydrous sulphuric acid; an acid containing 20 per cent., and likewise one of 43 per cent, conduct less freely; and one containing 64 per cent, much less. (De la Rive.)- The conducting power of watery liquids is increased by heat, probably because their decomposition is thereby facilitated. (De la Rive.)

The following substances, which are non-conductors in the solid state, become conductors when fused: Iodine (Inglis), ice, hydrate of potash, oxide of antimony, oxide of bismuth, protoxide of lead; the iodides of potassium, zinc and lead; protiodide of tin, protiodide of mercury; the chlorides of potassium, sodium, barium, strontium, magnesium, manganese, lead, zinc, and silver; terchloride of antimony, protochloride of tin, dichloride of copper; fluoride of potassium, fluoride of lead (sce the

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