340 SEC. 10. ELECTRICITY. 



3 480. Tangent Galvanometer, designed by Gaugain, for 

 measuring electro-motive force, resistance, &c. Elliott Brothers. 



The instrument is composed of two coils, separated by a distance equal to 

 one half their diameter ; contains three sections of stout wire, which can be 

 connected at pleasure. This instrument can be used with very powerful 

 currents. 



1481. Speaking Galvanometer, used for signalling through 

 submarine cables. The mirror and magnet are doubly suspended ; 

 glass in front and back protect the mirror and magnet from 

 draught and dust. Elliott Brothers. 



1482. Oil Vessel Galvanometer, as used in military schools, 

 for testing and signalling. Elliott Brothers. 



The coils consist of two sections of high and low resistance, which can 

 easily be brought into circuit by a switch in front of the instrument. To 

 reduce the oscillations of the needle, the instrument is provided with a glass 

 vessel for liquids, into which the vane of the needle dips. 



c. ELECTRO-DYNAMOMETERS. 



1472. Electro-Dynamometer. Apparatus for the deter- 

 mination of the strength of electric currents by measuring the 

 action between different parts of the current itself. 



H. Lloyd, Trinity College, Dublin. 



1483. Electro-dynamometer, for measuring electric cur- 

 rents which are constantly being reversed in direction. Made by 

 Dr. Meyerstein, of Gottingen. George Gore, F.R.S. 



1484. Edelmann's Absolute Dynamometer, 



M. Tli. Edelmann, Munich. 



1485. Fine-wire Electro-dynamometer. 



M. Th. Edelmann, Munich. 



d. VOLTAMETERS. 



1486. Voltameter. 



Geneva Association for the Construction of Scientific In- 

 struments. 



The tube of 1he voltameter is divided on glass into sixteenths of cubic 

 centimetres. 



1486a. Voltameter for teaching purposes. 



Physical Institute ( Univ. of Giesseri), Dr. Buff. 



This apparatus for the decomposition of water is described in Liebig's 

 Annalen, Vol. 93, p. 256. It is intended to render the gases evolved 

 available for analysis or otherwise. 



The connecting piece, fitted above with caoutchouc tubing, serves for 

 ordinary purposes. By means of the apparatus, not only may the recoustitu- 



