338 SEC. 10. ELECTRICITY. 



1452. M. Becquerel's Electro-magnetic Balance. 



Conservatoire des Arts et Metiers, Paris. 



1453. Pouillet's First Compass for Sines and 

 Tangents. Conservatoire des Arts et Metiers, Paris. 



1454. Sine-Tangent Galvanometer, for use at will either 

 as a sine or tangent galvanometer. Siemens and Halske, Berlin. 



1455. Aperiodic Galvanometer, with telescope and scale. 



Siemens and Halske, Berlin. 



The needle of this galvanometer is suspended in a copper ball, which acts 

 as a damper, preventing vibration in any new position given to the needle. 

 The needle itself is in the shape of a thimble cut away longitudinally on 

 opposite sides, and by this arrangement the magnetic intensity is considerably 

 increased, and the inertia of the magnet reduced. Du Bois-Raymond has 

 shown that the " damping " of an astatic needle can be carried so far that the 

 needle does not vibrate, but directly takes up its position of deflection, and 

 these he has termed " aperiodically vibrating needles." Dr. Werner Siemens 

 has attained the same end with simple non-astatic magnets, by means of 

 certain forms of the vibrating magnets, and of the damping copper mass. 

 The vibrating magnet consists of a steel thimble, from which two opposite 

 sides are cut away parallel to the axis. This horseshoe magnet vibrates in a 

 cylindrical space in a copper ball, which forms the centre of the wire coils. 



, j 1456. Inclination Galvanometer. Dr. Werner Siemens. 

 Intended for use particularly with the selenium photometer (ISo. 895). 

 The coil of the galvanometer is wound horizontally ; the needle vibrates in a 

 vertical plane and carries a mirror which reflects the image of a finely photo- 

 graphed scale (placed above) into the optical axis of a microscope. 



1457. Galvanometer for testing Lightning Conductors, 



constructed by the exhibitors for the .Prussian Royal Engineers. 



Kciser and Schmidt, Berlin. 



1458. Mirror Multiplier. E. Stohrer, Leipzig- 



1459. Galvanometer, showing both inclination and declina- 

 tion. E. Stohrer, Leipzig. 



The broad brass frame which carries the magnetic needle can be turned 

 about its .axis ; likewise the vertical .support in its base. Thus the needle 

 can be enabled to move in various planes, and the altered action of the force 

 measured by observation of the vibrations. 



145 9a. Current Measurer, with arrangement for very strong 

 electric currents. Gustav Baur, Stuttgart. 



1460. Edelmann's Mirror-galvanometer for absolute 

 measurements. M. Th. Edelmann, Munich. 



1461. Large Wiedemann's Galvanometer. 



M. Th. Edelmann, Munich. 



1462. Small Wiedemann's Galvanometer. 



M. Th. Edelmann, Munich. 



