Hartinann & Braun. Bockenheim- Frankfort o. M. 



171 



46. Reading Telescopes for observation with reflecting instruments. 

 3 different sizes with bright field, objectives of 30, 40, 55 mm aperture 

 and euroscopic micrometer oculars; micrometer adjustment in either 

 plane and vertical rack and pinion movement. Rigid structure*, entire 

 absence of iron. 



47. Simple Reading Telescopes of 27 mm aperture; with con- 

 venient scale support, for use in a horizontal and vertical position. Two 

 different patterns; one to be adjusted by hand, the other one by rack 

 and pinion. 



48. Lamp Stand and Scale for use with reflecting instruments, 

 w r ith petroleum burner, Argand burner or incandescent lamp. Scale 

 arranged to be observed from the front or from the back. 



49. Scales for mirror reading; very accurately divided in 

 lengths of 40. 60, 80, 100 120 cm, of wood T section, with narrow 

 paper strips, also transparent celluloid mounted in wood- lath; also 

 of plate glass, transparent or greyed, and of milk glass, the latter kind 

 being specially adapted for telescopic measurements. 



4S. 



44. 



50. Box Galvanometer, with bell magnet suspended by silk 

 fiber or quartz, in powerful damper with stopping spring; intelligible 

 arrangement; made to revolve on metal foot; with high or low resistance. 



Sensitiveness: at 5 ohms: 1 = 0.00005 amp. 



51. Aperiodical Differential Galvanometer with index reading; 

 very portable. Double wound multipliers, movable and interchangeable; 

 sensibility variable within wide limits. When the astatization is intro- 

 duced, which can easily be done, the sensitiveness at 100 ohms is: 

 If = 0.000 002 amp. 



52. Vertical Galvanometer, Deprez's principle; an exceedingly 

 handy instrument. 



Sensitiveness: 1 = 0.0001 amp. ; 



