INTRODUCTION 23 



work it out from that standpoint, the mechanical 

 steps first, designing a reduction gear that would run 

 constantly day and night with the least liability to 

 accident and the necessary changes of speed for the 

 fast or slow growing flowers. If the flower grew faster 

 or slower at certain periods of its life, or if the actual 

 dying or changing into its seed pod took too long, I 

 must speed it up on the screen by slowing the camera 

 down. 



The first motor gear I built is still running after 

 twenty years of service. The motor has worn out and 

 been replaced twice, but the gearing is as good as 

 ever. 



All the steps in this lapse-time photography pre- 

 sented their many difficulties which must be over- 

 comethe lighting, the effect of the light on the 

 growth of the plant or flower, the tiring of the plant 

 by the continuous twenty-four hour duplication of 

 day, what its size and position would be on the film 

 during its entire life and the correct exposure at the 

 various speeds at which the camera was running. A 

 motion picture camera exposes the film by a revolv- 

 ing shutter passing in front of it, the open part of 

 the shutter allows the light to pass and make the ex- 

 posure, the solid part stops the light while the film 

 is moving forward for the next picture. So the 

 amount of light is governed by the width of the 



