431 



ELECTRICITY. 



CCXLI1I. 

 Fig. Z. 



: ing the electricity generated during the excitation of 

 the cylinder. This apparatus is called an Electrical 

 Machine, aiul the metallic tube is named thr Prime Con- 

 ductor. Several of these machines, fitted up in various 

 ways, are represented in one of our Plates, of which we 

 shall afterwards (five a very particular description ; but 

 it is enough for our present purpose to know, that a 

 very high degree of electricity can be excited by the 

 simple apparatus which has been mentioned. 



Exp. 1. If, UJHMI a tube of glass highly excited by a 

 piece of silk, or by the human hand, we let fall any 

 light substance, such as a piece of gold leaf or thin pa- 

 per, the substance will be attracted to the tube, mid 

 then quickly repelled from it If the tube is made to fol- 

 low the body, it will still escape from it, till it meets 

 with some other substance which is a conductor, and is 

 not electrified. To this conductor it will impart all its 

 electricity, and being again attracted by the tube, will 

 experience another repulsion as before. This experiment 

 was first made by Otto Guericke. 



Exp. 2. Having electrified the prime conductor of 

 the electrical machine by exciting the glass cylinder, 

 bring near to the conductor a pith ball, or a small fea- 

 ther suspended by a slender wire, the ball will be at- 

 tracted by the conductor, and will continue to adhere 

 lo it till tile electricity of the conductor is dissipated. 



Exp. 3. If the ball or feather used in the preceding 

 experiment is suspended by a silk thread instead of the 

 metallic wire, it will at first be attracted by the conduc- 

 tor, and then immediately repelled, and will not return 

 to it again till it has imparted its electricity to some 

 conducting body. 



Eip. 4. Take a number of threads, from 10 to 18, 

 and about a foot long, and, having tied them together 

 at both ends, suspend them by the upper knot to the 

 conductor of the machine. As soon as the threads are 

 electrified, the lower knot will rise, and they will swell 

 out in the middle, and assume a spherical form. Tills 

 experiment was first made by Mr Wheeler. 



Eip. 5. Suspend a metallic plate, or a wooden plate 

 covered with tinfoil, either from the conductor of the ma- 

 chine, or from a separate stand connected by a chain with 

 the conductor; and at the distance of three or four inch- 

 es below it place a similar plate on a stand connected 

 with the ground. Put some pieces of gold leaf or thin 

 paper between these plates, and when the conductor is 

 electrified, they will be attracted and repelled alternate- 

 ly by the two plates, and will continue their motion as 

 long as the electricity remains in the conductor. 



This experiment is rendered doubly interesting, by 

 using small painted figures cut out of paper. These 

 figures will dance upon the lower plate as if they were 

 really animated, and will exhibit a number of attitudes 

 of the most singular kind. 



This experiment is excellently represented in Plate 

 CCXLIII. Fig. 2. where every part of the apparatus 

 is 'so distinctly seen as to require no description. 



Exp. 6. Place two small bells on separate glass pil- 

 lars, three-fourths of an inch distant, so that the bells 

 are insulated. Suspend by a silk thread a clapper, or 

 small brass ball, so as to hang in the middle between 

 the bells. One of the bells being made to communicate 

 by a conducting substance with the conductor of the 

 machine, and the other with the ground, the small bull 

 of brass will oscillate between the two bells, striking 

 them alternately, and producing an electrical chime. 



This experiment is still more interesting, if we hang 

 three bells upon a horizontal rod of brass commu- 

 nicating with the prime conductor. The two outer- 



most bells must be suspended by metallic wires or Diipdt# 

 chains, and the middle one by a silk thread, so as not 

 to communicate with the rod, but to have a communi- 

 cation with the ground or table, by means of a chain 

 going from the inside of the bell. A clapper or brass 

 ball is suspended by silk strings upon the same hori- 

 zontal rod, and between each of the two bells. As soon 

 as the conductor is electrified, the brass balls will he al- 

 ternately attracted and repelled by the adjacent bells, 

 and by striking against them, they will produce a chime 

 by no means disagreeable. 



This experiment is distinctly represented in Fig. 3. p LATe 

 Plate CCXLIII. A still more interesting variation of rrxi.UI. 

 the experiment is represented in Fig. 4. where n b is a F'B- * 

 rod of solid glass, supported upon a wooden stand, and F '8' * 

 passing through a perforated ball, No. 5. The other 

 end of the glass rod supports two metallic arms crossing 

 each other at right angles, having suspended at their 

 extremities, by means of wires, four bells, 1, 2, 3, 4. 

 From a point of each of these arms, equidi.-tant from 

 the extremity and the point of intersection, is suspend- 

 ed a brass ball by silk threads. Upon electrifying the 

 conductor, all the five bells will be set a ringing at the 

 same time. 



Exp. 7. Place upon the prime conductor a pointed 

 wire, and by means of it electrify the inside of a very 

 dry glass tumbler or jar. Place several pith balls on the 

 table, and cover them by the glass thus electrified. 

 They will immediately begin to leap up and down 

 against the sides of the vessel, and will thus be alter- 

 nately attracted by it and the table for a considerable 

 time. 



Exp. 8. Suspend from the prime conductor 'a cir- 

 cular ring of brass or any other metal, about a foot in 

 diameter, so that the ring is in a horizontal position. 

 Place below the ring a circular plate of metal of a 

 larger diameter than the ring, upon a stand like that 

 represented in Fig. 2, so that it can be placed at dif- 

 ferent distances from the ring. Take a very small hoi- 

 low ball of glass, blown extremely thin, and about two 

 inches in diameter, and having brought the surface of the 

 metallic plate to a distance from the ring less than its 

 diameter, place the ball within the ring, and upon the 

 plate, and as soon as the ring is electrified it will at- 

 tract the ball, which will be animated at the same time 

 with a rotatory motion, and a circular motion of trans- 

 lation. If the experiment be made in the dark, the 

 ball will appear luminous at all the points where it suc- 

 cessively touches the ring. 



Exp. 9. If the circular ring, in the preceding experi- 

 ment, is insulated, and stands about an inch and a half 

 from the flat surface of a table, and if a ball of glass, 

 about two inches in diameter, is placed upon the table, 

 and within the ring, it will first be attracted towards 

 the ring, and after touching the ring and becoming elec- 

 trified at the point of contact, this point will recede 

 and be attracted by the table, while the ring attracts 

 another part of the ball. Hence the ball will revolve 

 about its axis, and move round the circumference of 

 the ring. 



Exp. 10. Fix a piece of sealing-wax at the end of a 

 wire, and insert it into one of the holes of the prime con- 

 ductor. When the sealing wax is softened by heat, 

 turn the cylinder, and fine waxen fibres will be sepa- 

 rated from the wax, and if received on a sheet of paper, 

 will cover it with threads like red wool. By recei- 

 ving it upon paper, and afterwards gently heating it, 

 the result of the experiment will be rendered perma- 

 nent. 



