aphed while in flight with scarcely perceptible
distortion. A wheel revolving many hundred times a second can thus be
photographed, and appears to be stationary. Dr. Schillings has applied
this method to the photography of wild animals by night in the forests
of tropical Africa, and has published an interesting book giving his
photographic results. In order to take these pictures the track
followed by certain animals 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 photographs 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 feet 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 movement 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-minutes' film of
himself taken when fencing, giving 10,000 consecutive poses. He wished
to see exactly what movements he made, and to ascertain by this mi