MACHINE, ELECTRIC. 



point repelling the air must itself also be 

 equally repelled in the contrary direc- 

 tion ; whence the horizontal wire above 

 described is turned, and that always 

 one way, namely, contrary to that in 

 which the air is moved, or to the direc- 

 tion of its bent points. 



If an insulated conductor, free from 

 points, be brought within a certain dis- 

 tance of the prime conductor or cylin- 

 der in an electric state, it will also ex- 

 hibit signs of electricity of the same 

 kind; but if those signs be removed, 

 by taking the spark, and the conductor 

 taken from the prime conductor, it will 

 exhibit signs of the contrary electricity- 

 This is a very remarkable appearance, 

 but may be accounted for, if two suppo- 

 sitions be admitted, viz. first, that the 

 electric matter is attracted by conducting 

 bodies ; and secondly, that "the parts of 

 the electric matter mutually repel each 

 other, the forces of each power being 

 in a certain inverted ratio of the dis- 

 tance. 



For the electric matter, in an insulated 

 and uniform conductor, will then be equal- 

 ly diffused through its whole mass, and 

 the attraction which that conductor will 

 exert on any mass of electric matter pre- 

 sented from without, must be the excess 

 of the attractive force of the body over 

 the repulsive force of the electricity it 

 contains. Whence a given conductor will 

 attract the electric matter the most pow- 

 erfully, when the quantity it already pos- 

 sesses is the least possible, and its attrac- 

 tive force will decrease as it becomes 

 more saturated with electricity. Let two 

 equal conductors, composed of like mat- 

 ter, be brought within a small distance of 

 each other, then if the quantities of elec- 

 tricity they contain be equal, the attrac- 

 tions they mutually exert on those quan- 

 tities will be equal, and it will remain un- 

 disturbed in each body. But if one con- 

 ductor, A, contain more electricity than 

 the other, B, the attractive power of B 

 will be greatest, and will draw the elec- 

 tric matter from A, till an equilibrium is 

 obtained. It follows, also, that in a num- 

 ber of conducting bodies, communicating 

 with each other, the electric matter will 

 be every where of the same density, if the 

 greatest attractive force of the bodies be 

 supposed equal; but if different bodies 

 be supposed to attract the electric matter 

 with different forces, as is most probable, 

 the densities must vary with the forces. 

 This may be called the natural state. 



To apply this to the particular instance 

 above recited, suppose the end of an in- 



sulated conductor to be brought near the 

 prime conductor in a positive state, the 

 attractive power of the first mentioned 

 conductor is greater than that of the 

 prime conductor, yet, not being sufficient 

 to draw sparks, at the given distance, the 

 only effect it can produce is to make the 

 electric matter accumulate, and become 

 more dense in that part of the prime con- 

 ductor, near which it is presented ; by 

 which accumulation the rest of the prime 

 conductor becomes less electrified, as ex- 

 perience testifies. This accumulated bo- 

 dy of electricity repels, and consequently 

 rarifies the electric matter naturally con- 

 tained in that end of the conductor, which 

 is presented to the prime conductor ; the 

 rest of the fluid becomes more dense, and 

 the other parts of the conductor which is 

 presented, exhibit signs of electricity ; 

 yet, as this conductor in the whole con- 

 tains no more than its natural quantity, if 

 the electric state be taken off" by drawing 

 the spark, and it be afterwards removed 

 from the vicinity of the prime conductor, 

 it becomes negative throughout, by rea- 

 son of the loss of the spark. If a con- 

 ductor be presented to the prime con- 

 ductor in a negative state, the effects are 

 reversed, the attraction being strongest 

 at the prime conductor, and the accumu- 

 lation being in the conductor which is 

 presented, it exhibits a negative state, 

 which, being destroyed, upon removal it 

 becomes positive, by reason of the spark 

 which was given to it when apparently 

 negative. 



These effects are more considerable 

 the less the distance is between the two 

 conductors ; and the intercedent electric 

 body is peculiarly affected : the manner of 

 which may be better understood by ob- 

 serving the phenomena of non-electrics, 

 separa ed by electrics which are less lia- 

 ble to allow the passing of the spark than 

 the air is. 



Upon an insulated horizontal plate of 

 metal, lay a plate of glass, considerably 

 larger, so that there may be a rim of three 

 or four inches projecting beyond the me- 

 tal on every side. Upon the glass lay 

 another plate of metal, of the same size 

 as the former, so as precisely to cover it. 

 Electrify the upper plate, and the lower 

 will exhibit signs of electricity. Conti- 

 nue the electrization, and the lower plate 

 will emit sparks to an uninsulated body 

 for a time, and afterwards cease Sepa- 

 rate the plates from the glass without un- 

 insulating them, and the glass will appear 

 to be possessed of the contrary electrici- 

 ties on the opposite sides. That side 



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