INSTANTANEOUS PHOTOGRAPHY. 33 



After the series was finished, with the same short exposure two 

 single photographs were made : one of the dislv at rest, in order to 

 have the size of the white spot for comparison, and another of a 



Fig, 12. 

 — •--^|\|y\;VVIMA/lWWwvw »(yV\NVW\AW\AM 



man ascending stairs, in order to show the amount of detail ob- 

 tained with such short exposures. Subsequently all of these 

 results were carefully examined and worked up by several pro- 

 fessors of the University, whose reports stated : 1st, that the inter- 

 vals between successive exposures were equal except in two cases, 

 where they diiFered by a few ten-thousandths of a second ; 2d, 

 that the intervals between exposures shown by the photographs 

 and those shown by the chronograph were alike, or, in other 

 words, that the chronograph accurately recorded the intervals be- 

 tween exposures ; and, 3d, that the duration of the exposure was 

 less than one four-thousandth and more tiian one six-thousandth of 

 a second. 



Upon this third point the writer cannot wholly agree, but has 

 no reason to doubt that the efeeike action of light upon the sensi- 

 tive film was other than as stated by these gentlemen. 



Such very short exposures, however, were only necessary in 

 photographing small objects moving very swiftly, such as birds 

 flying, but the results obtained with them serve to show how great 

 are the possibilities of the application of instantaneous photography 

 in the future. 



