386 SEC. 10. F.LFXTKICITY, 



Made by the Geneva Association for the Construction of Scientific 

 Instruments. 



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

 Per rot, $ Sarasin, Geneva. 



A large sphere, made of wood, represents the earth. Two iron cylinders 

 represent the two extremities of the terrestrial magnetic axis. They pene- 

 trate into two globes filled with rarefied air, which simulate the higher 

 regions of the polar atmosphere. The electric discharge, which takes place 

 in this rarefied air, following rays all around a point situated in the prolonga- 

 tion of the terrestrial axis, turns about this point, and so turns in a different 

 direction at either pole, when the two cylinders are charged by means of a 

 horse-shoe electro -magnet, in accordance with the observations upon the 

 rotation of the rays of the Aurora Borealis. See " Archives des Sciences 

 physiques et naturelles," 1862, vol. 14, p. 121. Philosophical Magazine, 4th 

 series, vol. 23, p. 346. 



17 SO. Metallic Plates, for Watch Case, used by A. De la 

 Rive in his first experiments in galvanic gilding. 



Lucien De la Rive, Geneva. 



1745. Photographs of a Special Collection of Instru- 

 ments used by Volta. 



Royal Lombardian Institution of Science and Letters. 



IST PLATK : 



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 in the presence of Buonaparte. 



4. Original letter of Volta. 



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



the form of the lamps which Volta introduced so largely into 

 Germany. 



6. Apparatus employed in the first researches of Volta, for collecting 



and rendering appreciable the smallest quantities of electricity. 

 2ND PLATE : 



The same instruments on smaller scales. 

 SRD PLATE : 



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

 dated Como, 15th April 1777. 



1473. Apparatus for covering wire with silk for electric 

 purposes. H. Lloyd, Trinity College, Dublin. 



1751. Polar-light Apparatus. 



Prof. Lemstrom, Helsingfors, Finland. 



Report of a speech of Dr. Lcmstrom on his Polar-light apparatus, and the 

 theory of the Polar-light. 



This apparatus serves to prove that the polar light or aurora borealis is an 

 electric current flowing from *he higher regions of the atmosphere down to 

 the earth. 



