334 SEC. 10.^-ELECTRICITY. 



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 Hive in his researches. 



See "Archives de PElectricite " by de la Rive, 1841, Vol. 1, p. 280. 



1744. "Breguet" Thermometer, used and referred to 

 by A. de la Hive 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, 

 Per rot, fy Sarasin, Geneva. 



1745. Photographs of a Special Collection of Instru- 

 ments used by Volta. 



Royal Lombardian Institution of Science and Letters. 

 IST PLATE : 



1. Electrophorus, with mastic cake, designed by Volta. 



2. Condensing electrometer, the same which Volta made use of to 



demonstrate metallic electricity. 



3. Columnar pocket pile, adopted by Volta to demonstrate his theory 



at the Institute of Paris, Buonaparte being present. 



4. Letter of Volta in the original. 



5. Lamp for hydrogen gas, which is ignited by the electrophorus. It has 



the form of those lamps which Volta diffused so much in 

 Germany. 



6. Apparatus which served at the first researches of Volta, being 



available for collecting and rendering appreciable the smallest 

 quantities of electricity. 

 2ND PLATE : 



The same instruments on former scales. 

 3RD PLATE : 



Fac-simile of part of a letter of Alexander Volta to Professor Bartletti, 

 dated Como, 15th April 1777. 



1746. Galvanic Battery, by A. de la Hive. The Grove 

 Battery modified, with nitric acid on the exterior. Constructed 

 by the Geneva Association for constructing Scientific Instruments. 



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

 Perrot, fy Sarasin, Geneva. 



The nitric acid is placed in a large glass phial, whence it is unnecessary 

 to let it out. It is of 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 by a ground 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 fit for working 

 a Kuhmkorff coil. Two . elements suffice for a medium sized coil. De la 

 Rive constantly used this apparatus for his researches upon induced cur^ 

 rents, and always left it in his laboratory. 



1747. Floats, constructed by Gaspard de la Rive. 



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



Perrot, fy 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 upon a small floating battery. 



