Hnrtmarm & Braun. Bockenheim - Frankfort o. M. 



The remainder of the instruments constructed by this firm. 



In the centre case. 



38. Portable Telescope Galvanometer. Bell magnet in very 

 narrow copper piece effecting aperiodical damping; clamping for safe trans- 

 port; expeditious adjustment by means of circular level. Multipliers wound 

 with double convolutions, movable and interchangeable. Telescope attached 

 to instrument with scale placed at 25 cm distance. Suitable for all 

 galvanometric measurements occurring in workshop, laboratory and out- 

 door work. 



Sensitiveness without astatization at 100 ohms: 1 mm deflection 

 = 0.0000009 amp.; with astatization at 4000 ohms: 1 mm deflection 

 = 0.00000009 amp. 



39. Suspended Coil Galvanometer. A broad and homo- 

 genious magnetic field is obtained by a number of powerful magnets 

 having common poles. Movable bobbin suspended by quartz thread, with 

 safe clamping for transport. The current is admitted by extremely thin 



silver laminae. The oscillations are aperiodical also when no current is 

 passing and when high resistances are placed in the circuit. With index 

 and mirror reading. Also arranged for use as a differential galvanometer. 

 Sensitiveness at 10 ohms: 1 degree of index = 0.000005 amp., 

 or with mirror reading: 1 mm at 1 meter distance of scale = 

 0.000 000 1 amp. 



40. Micro-Galvanometer, Rosenthal's principle, with )( shaped 

 astatic magnetic system, the 4 poles of which dip into 4 small solenoids. 

 Great sensibility combined with small consumption of wire. Particularly 

 suitable for physiological and thermo-electric currents. 



Sensitiveness at 200 ohms: 1 mm*) = 0.000000006 amp. 



41. Astatic Reflecting Galvanometer with Nobili's magnetic 

 system inserted from the side and closely surrounded by the multipliers. 

 Adjustment of damping by means of various copper shells. 



Sensitiveness at 10 ohms and 10 seconds duration of oscillations: 

 1 'mm = 0.000 000 15 amp. 



