LAPSE-TIME PHOTOGRAPHY 35 



one-to-thirty worm gear was connected up with it 

 that made its shaft make one revolution in thirty 

 minutes. A good-sized wheel, 6" in diameter, was 

 fitted to it and then taper pins were carefully fitted 

 into its rim all equally distant from its center. One 

 pin would pass a given point every thirty minutes, 

 or as they could be put in as close together as re- 

 quiredthey could be close enough to have one pass 

 every minute, or 5-10-20 or 30 minutes, as often as 

 desired. Just above this slowly revolving wheel was 

 hung a pendulum-like rod. At its upper end, pro- 

 jecting above the wheel, a mercury tube switch al- 

 most balanced was installed. The pegs in the wheel 

 came along slowly, hitting a projecting arm on the 

 pendulum and caused the mercury to run to one end 

 of the tube, which made an electric connection with- 

 out sparking. This started a small motor that was 

 geared down to make a shaft run one revolution in 

 thirty seconds or a minute, as I desired, while the 

 long end of the pendulum was lifted up and held at 

 its highest point, high enough to keep the mercury 

 in its end of the tube giving an electric connection, 

 running the small motor connected with a reduction 

 gear running it until it had made one complete rev- 

 olution. This one revolution was connected with a 

 chain belt and sprockets to the camera, giving one 

 picture or frame. At the same time the motor started, 



