IX. RESISTANCE. 343 



1495. Universal Resistance-Box. 



Siemens and Halske, Berlin. 



This instrument is intended to measure by simple manipulation the resis- 

 tance of wires, the electro-motive force of batteries, and their internal re- 

 sistance. It has three branch resistances, and a complete series of resistances 

 from 1 to 10,000 S. U. 



1496. Complete Bridge. Siemens and Halske, Berlin. 



This bridge, besides the branch resistances, and variable resistance, in- 

 cludes battery reverser, galvanometer key, and short circulating keys, so 

 arranged that one of the branch resistances or the variable resistance can be 

 cut out instantaneously. 



1495a. Large Lane's Measuring Flask. 



Warmbruiin, Quilitz, 8? Co., Berlin 



1497. Edelmann's Small Rheochord. 



M. Th. Edelmann, Munich, 



1498. .Resistance Apparatus with Weber's absolute unite. 



M. Th. Edelmann, Munich. 



1499. Universal Compensator, for measuring resistances 

 and electro-motive forces. Prof- Beetz, Munich. 



The apparatus exhibited by Prof. Beetz was manufactured from his plans 

 by M. Th. Edelmann. 



1499a. Compensator, by Fresnel, made by Froment. 



Polytechnic School, Paris. 



1500. Post Office Resistance Coil, as used by the Govern- 

 ment telegraph authorities, for testing the resistance of telegraph 

 lines, cables, batteries &c. Elliott Brothers. 



These coils are constructed on the Wheatstone's bridge principle, and the 

 arrangement allows of the measurement of resistances from y^ to 1,000,000 

 ohms. 



1501. Dial Resistance Coil, for testing the resistance of 

 telegraph lines, cables, batteries, &c. Elliott Brothers. 



These coils are capable of greater accuracy than other resistance coils. 

 For each dial only one plug is used to bring the desired resistance in circuit, 

 for every change, therefore, the same number of plugs is necessary. 



1502. Preece's Balance, for comparing resistances in con- 

 nexion with a set of resistance coils. Elliott Brothers. 



This instrument is on the principle of the Wheatstone's bridge, and contains 

 four pairs of equal resistances, a commutator, and two keys. 



1503. Set of Resistance Coils, German silver, with Wheat- 

 stone's bridge, for testing the resistance of telegraph lines, cables, 

 batteries, &c. These coils allow of measurements of resistance 

 from T ^ to 1,000,000 ohms. Elliott Brothers. 



