292 SEC. 10. ELECTRICITY. 



1450. Patent Universal Galvanometer, indicating current 

 and resistance in definite units of measurement. 



John T. Sprague. 



This galvanometer contains four circuits, having ], 10, 100, and 1,000 fold 

 degrees of action on the needle, enabling it to be used for large or small 

 currents. The patent dial is graduated to indicate the current in actual units, 

 either the British Association Weber, or in chemical equivalents. It is also 

 graduated to show the total resistance of the circuit in Ohms without the aid 

 of a resistance instrument when used with a Daniell cell. By using a fixed 

 resistance it shows the electromotive force of the circuit in Volta. 



1450a. Galvanometer for Projections. 



M. J. Duboscq, Paris. 



l450b. Galvanometer, for thermo-electric currents. 



Luizard, Paris. 



1451. The Rhe Electrometer of Marianini, for observing 

 electric discharges between the atmosphere and the earth. 



Robert James Mann, M.D. 



This instrument was planned by Professor Melsens. It contains a coil of 

 copper wire which is to be made continuous with the system of a lightning 

 rod, or with the earth wire of a telegraph line. When an electric spark 

 passes through the coil a soft iron bar in its interior is magnetised, and a 

 traversing magnetic needle pivoted above the coil is then deflected out of 

 the north and south line of the earth's magnetism towards either the east or 

 west. When the interior iron has been magnetised it must be replaced with 

 a neutral bar before another observation can be made. 



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



Conservatoire des Arts et Metiers, Paris. 



1453. Fouillet's First Compass for Lines and 

 Tangents. Conservatoire des Arts et Metiers, Paris. 



1454. Sine-Tangent Compass. 



Siemens and Halske, Berlin. 



1455. Aperiodic Galvanometer, with telescope and scale. 



Siemens and Halske, Berlin. 



1456. Inclination Galvanometer. Dr. Werner Siemens. 

 Intended for use particularly with the selenium galvanometer (No. 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, 



for the Prussian Koyal Engineers. Keiser and Schmidt, Berlin. 



1458. Mirror Multiplier. E. Stohrer, Leipzig. 



1459. Galvanometer, showing both inclination and decima- 

 tion. E. Stohrcr, 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 



