180 Total Eclipse of .\>i,jast 7, 1869. 



this purpose. The cylinder was 6 inches in length and 10 



inches in diameter, driven by clock work regulated 1 >\ the 

 Frauenhofer friction balls. For securing a motion of sta- 

 ble equilibrium, an escapement held by a lighl spring was 

 connected with the shaft next to the friction balls, which 

 was regulated by a magnet beating every two seconds, by 

 opening and closing the circuit with the pendulum of the 

 clock. The sheets were previously ruled for every minute, 

 and the clock dots were recorded every two seconds. A 

 second pen was employed for recording the observations. 

 The connections were so arranged on the clock, that at the 

 end of every minute, the clock pen recorded in addition 

 the 61st second, thereby giving the zero of the clock with 

 absolute certainty — the whole mechanism performing in 

 a very satisfactory manner. In order to enable more than 

 one observer to use the chronograph during the progress 

 of the eclipse, wires were connected with the clock pen 

 and battery, so that observations could also be recorded 

 with it. It was so used by Mr. Lewis Swift. 



Another set of wires were connected with a battery and 

 local sounder-magnet, placed near the observers. This 

 magnet gave the clock beats for every two seconds and the 

 extra beat at the 61st second, by making connection 

 through the clock pen, causing it to act as a repeater. 



The Telescope. 



The telescope employed by myself was the Comet seeker 

 made by Alvan (Mark. The focal length is three feet six 

 inches, and the objective four inches clear aperture. A 

 parallel wire micrometer and position circle divided to de- 

 grees, was constructed for this work. There was one 

 fixed vertical and one horizontal wire, and three movable 

 micrometer wires. The eye-piece holder was so con- 

 structed that the eye-pieces belonging to the transit instra- 



