Apparatus for a Field IVorker loi 



inserted in the ordinary plate-holder in the same 

 manner as a plate. 



In my work I use the orthochromatic plates, to 

 the almost exclusion of all others, both with and 

 without the color screen, as I find that they in- 

 variably give me the best results. The beginner, 

 however, must experiment for himself until he 

 finds the plate which he considers best adapted to 

 his uses. 



