366 



HISTORY OF ASTRONOMY. 



declination are also 35 in number, and are arranged 

 in groups of five each. In order to prevent any con- 

 fusion between observations 

 for right ascension and those 

 for declination, the rule is-, 

 to observe for right ascen- 

 sion on one fascicle of wires 

 first ; then by a telegraphic 

 symbol, to denote the mag- 

 nitude of the star ; and after- 

 ward to observe it on a fas- 

 cicle of inclined wires for 

 declination. The several fascicles are distinguished from 

 each other by the inequalities of the intervals. 



Professor 0. M. Mitchell has invented a different 

 method of registering the declinations of the heavenly 

 bodies by means of the electric circuit, dispensing entirely 

 with the use of a graduated circle. For this purpose, he 

 attaches firmly to the axis of his transit instrument by a 

 strong clamp collar, a light bar, about six feet in length. 

 To the upper part of this arm an electro-magnet is fixed, 

 which operates a double lever armed with a steel record- 

 ing pen. To receive the record, a metallic plate is placed 

 vertically on the face of the transit pier, moving in ways 

 parallel to the circles described by the recording pen. 

 To use this instrument for record, the observer sets for 

 his standard star ; the arm is then brought to the vertical 

 and clamped. The instrument is then clamped, and a 

 tangent screw gives to the observer his slow motion for 



