432 



CATALOGUE. — ELECTRICAL APPARATUS. 



was moistened ; next the amalgani was applied, and lastly 

 Nooth invented the silk flap. The surface of a plate imme- 

 diately opposite to the cushion attracts the electric fluid ; 

 nothing therefore is gained by applying a cushion to it. A 

 piece of metal projecting forwards over the edge of the 

 cushion of a cylinder, considerably increased the intensity 

 ofaction, probably by increasing the capacity of the glass 

 in.its neighbourhood. If a piece of silk be applied closely 

 to the cylinder, it will attract the electricity on one side, 

 and emit it on the other, according to the direction in which 

 the cylinder is turned : but such an arrangement is not prac- 

 tically advantageous. If a cylinder be well greased, so as 

 to become opaque, and the silk flap be made semitranspa- 

 rent with the grease, the amalgam be then applied with 

 leather to the cylinder, and pressed against it as long as the 

 friction continues to increase, the action of the machine 

 will be very powerful. When a nine inch cylinder had been 

 tl-.us treated, the conductor gave flashes to the table on 

 which it stood, at the distance of 1 4 inches. A square foot 

 of a jar was fully charged by the friction of 1 8 or 1 9 feet of 

 the cylinder : the machine at Haarlem required at first the 

 friction of 00.6 feet, and with a single cushion would have 

 required half as much. This cylinder was equal in effect to 

 the great Teylerian machine, whifh was thirty times as ex- 

 pensive -, but afterwards Van Marum tripled the effect of the 

 Tevlcriao raachiae. 



Ctithbertson iiber die veisuche von Dei- 

 man n und Troostwyck. 

 Pearson's portable electrical machine. Nich, 



I. 50G. 

 An electrical macbine of silk. Nich. II. 4eO. 

 Fell's pocket ribbon machine. Nich. HI. 4. 

 Cirinini on a large electrical machine. Gilb. 



IV. 3.39. 

 Wolff's electrical machine. Nich. VII. 124. 



With improved rubbers. 



Galvanic batteries. See Chemical Electricity, 



Gcuan applied liquid mercury as a rubber. 



Ingenhousz's portable machine is a varnished ribband, 

 hung on a fixed pin or nail, and rubbed with a cat's skin : 

 the little jar which is charged is held near the rubber, and 

 collects negative electricity from the ribband 



Lichtenbcrg's drum machine is of wood, covered with 

 black woollen cloth. Gutle's electrical machine o f woollen 

 is said to be cheap and powerful. 



The best cement for a cylinder consists of 5 parts of resin, 

 4 of bees wax, and a of powdered red ochre. The silken 

 flap is made of black mode. Cavallo. 



Amalgams. 



Woulfe on the aurum mosaicum. Ph. tr- 



1771. 114. 

 It was made of mercury, tin, sulfur, and muriate of am- 

 monia. 

 Higgins's amalgam. Ph. tr. 1778. 861. 



Four parts of mercury with one of zinc. 



Kieniueyer's amalgam. Rozier XXXHI. 96- 



Two parts of mercury, one of zinc, and o.ie of tin. 



Neret's amalgam consists of equal parts of tin and mer-. 

 cury : Cuthbertson uses mercury with tin filings and a little 

 oil. 



The amalgam of tin is made with two parts of mercury 

 and one of tinfoil, adding a little powdered chalk. Cavallo. 



For the amalgam of zinc, melt one part of zinc, and 

 shake it in a wooden box with 4 or 5 parts of mercury, 

 heated above the temperature of boiling water : then triturate 

 it with a little tallow and a very little powdered wniting; 

 and add one fourth of the amalgam of tin. Cavallo. 



Elect rophorus. 



-Wilke. Schw. Abh. 1762. XXXIX, 54, II6, 



200. 

 Beccaria Electricitas vindex. Gr'az. 

 Volta. Scelta di opusc. Milan. X. 37. Roz. 



Vlll. 21.Sept. 1776. Ph. tr. 1782. llozier, 



1783. Brugnatelli bibl. fis. 

 Volta on the passage of electricity through 



imperfect conductors. Soc. Ital. V. 551. 

 Henley. Ph. tr. 1776. 513. 

 Achard A. Berl. 1776. 122- 

 Achard. Schr. 226. 

 Cavallo. Ph. tr. 1777. II6, 388. 

 On the electrophorus. A. Petr. I. i. H. 70. 

 Kiafft's theory of the electrophorus. A. Petr> 



1. i. 154. 

 Ingenhousz Elements of electricity, 

 liigonhousz. l"h. tr. 1778. 1027. 

 Socin Anfangsgrlinde. iian. 1778. 1792- 

 Picket Expenmenta physicomedica. 8. 

 Wuiizb. 1778. 



