EFFECTS, ETC.] UNDULATORY FORCES. ELECTRICITY. 



181 



states are occasionally represented by the mathematical 

 signs of -f- and (phis and minus). 



We have confined our attention to one sheet or plate of 

 glass only ; and before proceeding further, we may ob- 

 serve, that the thickness of the glass has a decided effect 

 on the readiness with which the two sides may be polar- 

 ised. This arises from two causes namely, the distance 

 between the sides, and the partial polarisation which the 

 material itself undergoes. It is therefore essential, in 

 making a Leyden jar or battery, that the glass employed 

 should be as thin as possible, as on that depend both the 

 facility of charging and discharging the arrangement. 



We shall now examine the effect produced on a num- 

 ber of particles, with respect to the electrical arrange- 

 ment which they assume when in an excited state ; and 

 we shall represent the quiescent and active condition 

 by means of a diagram, which will assist in conveying 

 the subject in an intelligible manner to our readers. 

 For this purpose, we shall suppose the following arrange- 

 ment to represent the twofold state to which we have 

 alluded. Of course, we do not intend to assume that 

 the particles we speak of are those of electricity. We 

 presume that they are the atoms of a body, in which 

 electricity is respectively in a latent and active form. 



No. 1. NP N. 



No. 2. 



NP 



PN 



KP 



PX 



We here suppose the existence of four atoms of a 

 body, whose sides are respectively negative and posi- 

 tive ; but in No. 1, such states are those of latent or 

 combined electricity. If, however, by means of the 

 electrical machine, we induce an actict state, then the 

 previous electrical equilibrium is at once disturbed ; and, 

 ai we observe in No. 2, the electricities arrange them- 

 selves so that at each end of the series of atoms we have 

 a free electricity ; and, intermediately, the electricity of 

 one atom instantly acts on, and induces action on, that of 

 its neighbour. If a connection be made between the oppo- 

 site electrical states, at the extremities of the series of ex- 

 cited atoms, then they are at once restored to the condition 

 shown in No. 1, and the equilibrium is thereby reproduced. 



It will thus be perceived, that electrical induction 

 takes place when an excited body is brought near to one 

 in a quiescent state ; that the effect produced is that of 

 arranging the electricities of the previously unexcited 

 body in a polar state ; and these laws hold good, no mat- 

 ter how many particles may be affected, provided that 

 the exciting power is of sufficient energy. 



It will be presumed, in all future experiments, that 

 our readers will bear these facts in mind, and that when 

 we speak of induction, they will fully understand the 

 term in all its bearings. 



We shall next proceed to illustrate the various effects 

 which a powerful charge of electricity, as afforded by 

 means of the Leydon battery, produces ; and shall divi.l.- 

 these into mechanical, luminous, calorific, and physiolo- 

 gical phenomena; although, occasionally, two or more of 

 these classes are simultaneously produced by the same 

 experiment. 



THE MECHANICAL, LUMIXnrs. AND OTHER 

 EFFECTS OF ELECTRICITY. 



WE shall now suggest numerous experiments which 

 Fig. M. CMII be tried by the Leyden 



jars or battery, in which the 

 various effects of a powerful 

 charge of electricity will be ex- 

 hibited ; and shall also ex- 

 amine some natural phenomena 

 in which that force is the active 



t of the experiments we 

 shall introduce, may be tried by 

 means of a plate machine of 

 from twelve to eighteen inches 

 in diameter in the glass plate, 

 and with a battery of from two to four jars. To facili- 

 tate the construction of an arrangement of the kind, wo 



Filf. 27. 



I refer to Fig. 20, which represents a battery of four jars, 

 I of about three pints capacity each. Such is sufficient 

 for a vast variety of experiments, and each jar may be 

 of the simple kind we have already described.* 



The different parts of this Leyden battery correspond 

 in every respect, except as to size, with that illustrated 

 at a previous page, t Before commencing any experi- 

 ment with the battery, care should be taken that the 

 outside of the jars be connected with some good con- 

 ductor, such as a gas, drain, or water-pipe, as on that 

 will depend much of the success which may be desired. 

 As it is impossible to separate the mechanical, luminous, 

 and calorific effects of frictional electricity, we shall in- 

 troduce our experiments without reference to such dis- 

 tinctions ; pointing out, however, as we proceed, any 

 notable matter which may arise. 



Exj>eriment 23. Combustion of Mttal Leaves. For 

 this purpose, a narrow strip of gold or silver leaf is to 

 be pasted on paper. The width of the strip of metal, 

 as well as the length, depends on the power of the bat- 

 tery ; but a strip of an eighth of an inch wide, and eight 

 inches long, may be used. The paper should be well 

 dried ; and strips of several metals may be then pasted 

 on it. The paper so covered is to be fastened on to a 

 well-dried board, and one end of the metal strip is to be 

 attached, by means of a wire, with the outside of the 

 battery. The other end of the strip may be connected 

 with the knob of the discharger at a illustrated already. J 

 To the other knob, marked /, the inside of the battery 

 must be attached by a wire. By such means the charge 

 will spontaneously discharge itself. In the absence of 

 such an arrangement, the ordinary discharger may be 

 used, one of its ends being brought into contact with 

 the inside of the battery by means of a wire ; and its 

 other end, after the battery is cliai ^-.1. is to be brought 

 in contact with 

 the strip of metal. 

 On the charge be- 

 ing thus directed 

 over the metal 

 strip, a loud ex- 

 plosion will take 

 place, and the me- 

 tal foil will be de- 

 stroyed. The ef- 

 fect on the paper 

 is often very 

 pretty, owing to 

 the dispersion and 

 oxydation of the 

 metal in all direc- 

 tions. The mode of carrying out this experiment is illus- 



iu Fig. 27. 



I-', j- 1 "i- 1 incut 24. Gunpowder may bo ignited by means 

 of the Leyden jar, if the charge be arrested in its course 

 by means of a piece of moistened string. When the charge 

 is sent directly to the powder by a wire, it will be simply 

 dispersed. To ignite it, place the gunpowder on a plate, 

 and dip into it a wire proceeding from the outside of two 

 jars. Attach a piece of wet string to one knob of the 

 discharger, and to the end of the string fix a piece of 

 wire, which is to rest on the gunpowder, at a short 

 distance from the end of the wire proceeding from the 

 outside of the jars. When they are fully charged, bring 

 the other knob of the discharger into contact with their 

 inside coatings in the usual manner, and the powder will 

 be at once ignited, ffig. 28 shows the proper iethod 

 of conducting the experiment. 



Experiment 25. Two very singular effects may be 

 produced, by causing the Leyden discharge to pass 

 between vwo plates of glass. A narrow strip of gold 

 leaf is to be placed between two slips of common 

 window-glass, which may be an inch wide and four 

 inches long. These should be tied tightly together, 

 and the metal leaf should extend about half an inch 

 beyond each end. One end of the leaf is to be at- 

 tached to the outside of the battery, and the plates 

 should be insulated by placing them on two guides. 



See ante, p. 180. 1 Ante, p. 178. t Ante, p. ISO ; Fig. 23. 



a a t c r, represent two itrips of metal leaf pasted 

 on a shed of p.i prr ; b ti illustrate the appear- 

 ance of a strip of metal already exploded; d 

 il a wire proceeding from the disrluiKi-r, by 

 meant of which the thai ire of the buttery ha 

 paascd ; e is a wire connected with the out- 

 side of the butu-r y. 



