268 SEC. 10. ELECTRICITY. 



ISOlb. Thermo-Electric File of Hydrogenium. 



Prof. Dewar. 



Consists of alternate layers of Palladium and Hydrogenium ; electro- 

 motive force equal to that of iron and copper. 



d. INDUCTION COILS. 



1302. A Small RuhmkorfF's Induction Coil. 



Rob. Voss, Berlin, 



1303. Ruhmkorff's Coil. Frederick Guthrie, F.R.S. 



The current from a galvanic battery passing down a spiral of copper wire 

 excites a magnet, which by its attraction so moves a steel spring as to 

 interrupt the current. The current being thus broken, the magnetism ceases 

 and the current is restored. The result is a very rapid making and breaking 

 of the current in the spiral or primary. Inside the primary are bars of 

 soft iron ; outside, many miles of fine insulated copper wire called the 

 secondary. Connected with the primary by wires, one on each side of the 

 make and break, is a tin-foil condenser. This absorbs the extra-current 

 when the primary is broken, and acts to augment the secondary when the 

 primary is made. The interior magnetism acts in the same direction. 



1303a. First Induction Machine, called " de Fixii," 

 constructed under the direction of Ampere. 



College of France, Paris. 



1304. Six-inch Induction Coil, and Browning's Spark 

 Condenser, for obtaining spectra of metals by the induction 

 spark. John Browning.- 



When using the spark condenser the amount of coated surface introduced 

 may be varied at pleasure, and the density of the spark thus regulated. 



13O4a. Apps' Fatent Induction Coil, giving sparks of 

 17 in. in air, with a battery of five Grove's cells, platinum, 

 5 x 3 in. immersed. Alfred Apps. 



1304b. Henry's Induction Coils. 



Museum of King George III., King's College^ London. 



1305. Large Induction Coil, with Foucault's break ; will 

 give 18-inch sparks". A cube of glass was pierced by this coil. 



M. Ruhmkorft'. 



1305a. Electric Necessaire, containing Ruhmkorff bobbins. 



M. Is)iseau, jun., Paris. 



1306. Induction Apparatus for medical purposes. 



Keiser and Schmidt, Berlin. 



1307. Induction Apparatus for medical purposes. 



Keiser and Schmidt, Berlin. 



1308. Induction Apparatus for medical use. 



Keiser and Schmidt, Berlin. 



