36 PICTURING MIRACLES 



the electric lights came on, giving the correct amount 

 of illumination required for the exposure. Just as 

 the same shaft that was connected with the camera 

 by its chain belt made its complete revolution an 

 arm kicked off the holding lever of the pendulum. 

 Stopping itself it would swing back to its vertical 

 position, the mercury would flow away from the con- 

 necting end of the tube without a spark as most 

 switches do when the current is broken (the sparking 

 soon corrodes and gives trouble), the lights would 

 go out, the motor stop and nothing more would 

 happen until the next taper pin in the so-called clock 

 wheel came along and started the chain of opera- 

 tions again in one minute or in 30, depending upon 

 how many taper pins you had in the wheel. This 

 description may seem complicated but by looking at 

 the picture you will see that it is very simple, and 

 the camera always takes the same time for each expo- 

 sure, regardless of the interval between them which 

 can be changed by removing or inserting more taper 

 pins. If the rim of the wheel is at least 14 " thick and 

 the standard taper holes made carefully, just putting 

 them in with the fingers will hold them, or small 

 screws will answer the same purpose. 



It is very simple to make a device that will start a 

 motor and camera, but the trouble comes in getting 

 it to stop at just the right moment, and with the 



