PHOTOGRAPHS BY ELECTRIC SPARK 73 



has to be detected, and then a thread is stretched " breast- 

 high " across the track, so that the animal coming along it 

 by night shall pull the thread. Immediately the thread is 

 pulled it sets an electric contact in action. There is a brief 

 flash of one two-thousandth of a second, and a picture is 

 taken by a camera previously fixed, out of harm's way, so 

 as to focus the area where the thread was stretched. 



Dr. Schillings obtained some very remarkable photo- 

 graphs of " the night life of the forest " in this way lions 

 and leopards advancing on their prey were suddenly 

 revealed, and the helpless antelope or other victim was 

 shown crouching in the dark, or making a desperate effort 

 to escape. 



The electric-spark method was applied by a friend of 

 mine to demonstrate the movements by which a kitten 

 falling backwards from a table succeeds in turning itself so 

 as to alight on its feet. During a fall of less than 3 ft. he 

 obtained five successive spark-pictures of the kitten, which, 

 I beg it may be clearly understood, was a pet kitten, and 

 was neither frightened nor hurt by the proceedings. 



Instantaneous photographs, whether obtained by the use 

 of an electric spark as a means of illumination, or by 

 the less rapid method of a spring shutter working in 

 combination with a sensitive film, which is jerked along 

 so as to be exposed when the shutter is open and travel 

 when it is shut, has been applied to the analysis of 

 other movements than those I have mentioned, and has 

 yet to be applied to many more, such as the crawling of 

 insects and millipedes, and the beautiful rippling move- 

 ment of the legs and body by which many marine worms 

 swim. It has been extensively used in the study of 

 human locomotion, and of the successive poses of the arms 

 and legs in various athletic exercises, and in such games 

 as baseball and golf. 



A first-rate fencer of my acquaintance had a five- 



