1900] MICROSCOPICAL JOURNAL 19 



Photo-Mircography With Opaque Objects. 



W. H. WALMSLEY. 



Any microscope, with or without incliuation to body, 

 may be used. The results are better with, than without 

 any ocular, and the latter should be, if possible, especi- 

 ally constructed for the purpose — as Zeiss' projection eye- 

 piece for example. It should be capable of carrying and 

 focusing a three-inch objective, which power is useful for 

 many comparatively large or coarse objects. The outfit of 

 lenses should include a two-inch objective but need not 

 go above, 1-5 the most useful work being done withl^-in. 

 to £-in. A plano-convex or bull's eye condensing lens on 

 stand is indispensable. If possible, alvieberkuhn for each 

 objective and a parabolic silvered reflector should be in- 

 cluded in the outfit, though the latter pieces of apparatus 

 are rarely found in these days with any microscope, es- 

 pecially of American manufacture. 



Artificial illumination may be used ; even the some- 

 what dim coal oil lamp, which, however, requires inordin- 

 ately longexposures. The acetylene gas light is altogether 

 the best from an artificial source I have ever employed, 

 and is quite satisfactory in time and quality. But alto- 

 gether the best light for the purpose is diffused daylight 

 from a window with northern exposure, than which noth- 

 ing can possibly be better. 



If, however, the camera is constructed so as to per- 

 mit the use of the microscope in a vertical position, so 

 much the better, as proper lighting of the object is more 

 readily secured than when the instrument is inclined hor- 

 izontally, an even illumination, avoiding deep shadows, 

 giving the best results in most cases, and this is the more 

 readily obtained when the object lies in a horizontal plane. 

 Some objects are better shown under a diffused light,such 

 as may be obtained near a window without the interposi- 

 tion of a condenser. If its color be dark or reflect but 



