ELEMENTARY PHOTO-MICROGRAPHY. 89 



not absolutely at rest ; hence many amateurs 

 will welcome a method that places in their hands 

 a convenient process of photographing objects in 

 motion. Experiments were first made with fresh- 

 water polyzoa, Lophopus crystallinus, expanding its 

 tentacles a movement not too rapid for good 

 definition at i-3oth second. The microscope was 

 horizontal with object in vertical cell on the stage, 

 which was focussed by properly adjusted trans- 

 mitted light from oil lamp in the ordinary way, 

 and provision was made for replacing the lamp 

 by a tin dish containing " Agfa " flashlight powder 

 on a retort stand arranged to bring the powder 

 in the position previously occupied by centre of 

 lamp flame, the top of powder being at the level 

 of bottom of flame. Ignition can then be made 

 at a suitable moment by means of a long taper 

 or red-hot wire. 



To ascertain the most advantageous time for 

 exposure, a dim light should be thrown on the 

 subject obliquely either from behind or in front, 

 sufficient to reveal the outlines when looked at 

 through a hand magnifying glass. The other lights 

 in the room should then be lowered, and the 

 shutter of dark slide withdrawn. 



Standing in readiness for any desired display 

 of outline, it is easy to fire the powder very quickly. 



Some well defined negatives were secured when 

 using 2in. objective with X5 eyepiece. It is 



