ELECTRICITY. 



4G9 



Bagen 



e>.ptri- 



Posi/ree elfdricily was produced by the following 

 w hen sifted on the cap of the electrometer. 



Charcoal of wood, 

 Sulphate of potash, 

 Nitrate of potash, 

 Acetate of lead, 

 Oxide of tin. 



Wheat flour, 



Oatmcnl, 



Lycopodium, 



Quassia, 



Powdered cardamom, 



Electricity 

 produwd in 

 the electric 

 column 

 discovered 

 by DLuc. 



Pi ATE 



o xi.v. 

 Fig. 8. 



When the bodies in the two preceding Tables were 

 sifted either through a sieve of hair, flannel, or muslin, 

 the same kind of electricity was always produced. 



In applying the second method, Mr Singers broke 

 the pure alkalies into small pieces, and exposed them 

 in an open phial, for a quarter of an hour, to a mode- 

 rate heat, which was not great enough to fuse the al- 

 kali. It was then quickly reduced to powder in a 

 warm and dry mortar, and instantly distributed over a 

 dry sheet of card paper, which, during a certain time, 

 he found to attract the moisture from the alkali, as fast 

 as the alkali attracted it from the air. In this way lie 

 obtained the following results, the copper plate being 

 always electrified in an opposite manner to that of the 

 powders. 



Positive Electricity. 



Lime, Pure potash, 



Barytes, Common pearl ashes, 



Strontites, Carbonate of pota>li, 



Magnesia, Carbonate of soda, 



Pure soda, Tartaric acid. 



Negative Electricity. 



Benzoic aid, Alumine, 



Boracic .-: Carbonate of ammonia, 



Oxalic acid, Sulphur, 



Citric acid, Rosin. 



SOex, 



From the circumstance of sulphur and rosin giving 

 the same kind of electricity when touched with a cop- 

 JHT plate, as that which is produced by friction, Mr 

 Singfi-i supposes, that the contact of dissimilar bodies 

 is in general the primary source of electrical excitation. 

 ' 'avallo's Electricity. Ben net, /'A/7. Trans. 1787, 

 vol. Ixxvii. p. 26. Singers' Elements of Electricity and 

 Electro- Chemistry, App. 9, p. 473 470'. 



SECT. VI. On tlif Electricity produced in the Electric Co- 

 lumn discovered by De Luc. 



As the electricity generated in the electric column 

 has no appearance of being produced by chemical ac- 

 tion, the consideration of it belongs more properly to 

 electricity than to galvanism. 



The electric column invented by that ingenious phi- 

 losopher, .1. A. De Luc, consists of several hundred small 

 discs of zinc and gilt paper placed upon each other alter- 

 nately, and inclosed in a glass tube. Whm thr number 

 of discs amounts to 800 or 1(XK), the apparatus will, at 

 any time, produce a perceptible effect upon the electro- 

 meter without any preparation. The electric column 

 is represented in Plate CCXLV. Fig. 8. The column is 

 represented at ATS, supported horizontally on two rods 

 1,1, made of solid glass, coated with sealing wax or any 

 other insulating varnish, and fixed by female screws on 

 the wooden bar 2, 2. It consists of 600 groups form- 

 ed of plates of zinc, seven tenths of an inch in dia- 

 meter, and equal pieces of plain gilt Dutch paper (which 



is paper covered with copper,) the upper side of which 

 being turned towards A, thus becomes the positive ex- 

 tremity of the column ; and since the paper seems on- 

 ly to separate the binary groups of zinc and copper, 

 tlie latter being in each of them on the side of B, this 

 becomes the negative extremity of the column. The 

 groups of zinc and Dutch gilt paper are contained be- 

 tween three glass rods, coated with sealing wax, and 

 fixed in holes of the brass plates A, B, where they must 

 be inserted while the plates are hot, and the holes fill- 

 ed with sealing wax. In the lower part of these brass 

 plates is a pin, which enters freely into the brass cap at 

 the top of the pillars 1,1. Two screws 3, S, formed on 

 the outside in the shape of loops, pass through the brasi 

 plates A, B, and serve both to press the groups against 

 the glass rods, and to form a communication between 

 the extremities of the column and the electrometers M, 

 N, as represented in the Figure. In order to deter- 

 mine the electric state of different parts of the column, 

 a third electrometer P is used. It is shewn in the Fi- 

 gure as connected with the centre of the column by a 

 loop upon a thick brass plate, but when it is required to 

 examine die state of other parts of the column, it may 

 be made to communicate with any point of it by the in- 

 U'vpiiiition of a soft wire held in the middle by an in- 

 sulating handle. For some experiments, brass hooks 

 5 and 6 are fixed to the brass plates A, B, and project 

 about an inch ; and in experiments on the conducting 

 faculty (/!' ^1 -iss tubes filled with water, the tube TU 

 may be hung at the point of a hook upon the wire 

 sii-pemlcd by silk threads 7, 10, 11 passing over the 

 pulley 10, and descending to a thin brass plate 11 fixed 

 at the base of the instrument. The other wire 9 of the 

 tube is hooked to the projecting wire 6. 



In order to accommodate the instrument for exhibi- 

 ting the electrical state of the atmosphere, De Luc fix- 



ed at the top of one of the pillars of the column at its 



,.,1111 e i 



positive extremity, a brass piece 13 held by a tern lie 



screw, and projecting forwards about l.J inch. On 

 this projection is fixed, by means of a screw, another 

 brass piece, having on one side a vertical groove 1 K 

 A brass rod is held in this by a pin, and at the lower 

 end of the rod is a IMM-S ball \F>, which can be brought 

 backwards and forwards. From the top of the rod 

 projects a bra-s loop 16', to which is suspended by the 

 finest silver wire a gold ball 17. The ball is fixed 

 at one extremity of a piece of brass 28, lying on two in- 

 sulating pillars 27, 27, upon the lead bars 19, 19. A 

 brass spring 23, moveablc backwards and forwards up- 

 on pins 20, 20, about half an inch in breac i at the base 

 24-, is fixed into the piece 24-, where it passes under the 

 bent part of an upright brass piece '25. The breadth 

 of the spring 23 diminishes towards its end, where it is 

 terminated by a brass wire bow 22, across which is 

 stretched the fine silver wire 21. At the top of the 

 upright brass piece 25, is a screw 26, which presses the 

 spring 23 for the purpose of giving a small motion of 

 adjustment to the wire 2 1 . 



Whi'ii the instrument is thus constructed, the leaves 

 or fibres of the electrometer M will diverge with posi- 

 live, and those in N with negative electricity ; but 

 when the finger is laid on either of them, in order to 

 produce a communication with the ground, the diver- 

 gency will cease in that electrometer, and become nearly 

 double in the other. When the finger is removed, and 

 the column left . to its own operation, the divergencies 

 are not restored to their former state, half an hour or an 

 hour being necessary to reproduce them. If an insulated 

 body, however, electrified cithcrpositively or negatively, 



Descriptive 



P ' ATE 



Method of 



construct- 



j"B tll ':' co - 

 lunin lor an 

 acr ; a i e ] cc . 



troscopc. 



Electrical 

 properties 



