for Atmospheric Electriciti/ 



3 



rotates once in one hour. Two scales of measurement are thus 

 possible and both have been employed. No difficulty was found in 

 taking twenty-four, or two hour records, for although the records 

 overlapjjed it was (|uite easy to distinguish one part from the other. 

 A light zinc tube was slipped over the clock-case to give a good 

 support for the bromide paper which was wrapped round outside. 

 The whole clock was made to balance by fastening small pieces of 

 lead to the inside of the case, but during the working a little 



Fig. 2. 

 hour hand arbor fixed by the pin P. 



Fig. 1. 

 The electrometer. 



irregularity occurs as a consequence of the unwinding of the spring; 

 this however is not very great and a number of clocks could be 

 made to keep time together. The recording cylinder was enclosed 

 in a light tight case with a long narrow slit in front, Fig. 2. 



(3) Illuminating system. As the apparatus was used out of 

 doors, a lamp was unsuitable as a means of illumination, so that 

 daylight was used and found to be very suitable. The electrometer 

 and recording cylinder were placed at the opposite ends of a light 

 tight box measuring 20 x 17 x 14 cm. A hole was made in the 



1—2 



