384 SEC. 10. ELECTRICITY. 



A bell-glass stands upon a plattcn, which, itself must be placed upon the 

 pole of an electro-magnet. This glass being filled with rarefied gas, the 

 electric discharge is completely effected between the central brass ball, and a 

 ring of the same metal constituting the other electrode. A sail-wheel is 

 adjusted inside this ring, so that its vertical paddles may be upon the direct 

 line from the ball to the ring, whereby the discharge strikes it in revolving 

 under the action of the magnet. It then gives it a rotatory direction as soon 

 as the direction of the magnet is changed. 



(See Archives des Sciences, vol. 45, p. 387; Philosophical Magazine, 

 vol. 44, p. 149.) 



1743. Induction Coil by Bonijol, an old Genevesc maker. 

 De la Rive Collection. The property of Messrs. Soret, 



Perrot, fy Sarasin, Geneva. 



Bonijol constructed a great number of electrical apparatus under the direc- 

 tion and with the advice of G. and A. De la Hive. 



This coil, in which by means of a single medium sized element of constant 

 power, induced currents of considerable force may be produced, was frequently 

 used by A. de la Rive in his researches. 



See "Archives de 1'Electricite " by De la Rive, 1841, Vol. 1, p. 280. 



1744. "Breguet" Thermometer, used and referred to 



by A. De la Rive in his works upon the causes of voltaic electri- 

 city, and upon the properties of magneto-electric currents. 



De la Rive Collection. The property of Messrs. Soret, 

 Perrot, fy Sarasin, Geneva. 



1746. Galvanic Battery, by A. Be la Rive. Modifica- 

 tion of the Grove Battery, with nitric acid on the exterior. Con- 

 structed by the Geneva Association for the Construction of Scien- 

 tific Instruments. 



De la Rive Collection. The property of Messrs. S'oret, 

 Perrot, Sarasin, Geneva. 



The nitric acid is placed in a large glass phial, and in sufficient quantity 

 to serve for a long time without being changed. 



The diaphragm containing the acidulated water and the zinc closes perfectly 

 the orifice of the phial ; when the battery is taken to pieces, this diaphragm 

 is replaced b}- a glass stopper. By this arrangement, the disengagement of 

 nitrous vapour is avoided. This battery may thus safely remain in the 

 experimenting room, close to the apparatus, and is especially suited for 

 working a Ruhmkorff coil. Two elements suffice for a medium sized coil. 

 De la Rive constantly used this apparatus for his researches upon induced 

 currents, and always left it in his laboratory. 



1747. Ploats, constructed by Gaspard de la Hive. 



De la Rive Collection. The property of Messrs. Soret, 

 Pcrrot, Sf Sarasin, Geneva. 



Apparatus intended for the demonstration, in a simple manner, of the 

 " Laws of Ampere " upon the reciprocal action of currents. The conductors 

 can be adapted directly to a small floating battery. 



