56 PRACTICAL PHOTO-MICROGRAPHY. 



" ortho " plates, may be taken as " safe." To test a light for 

 safety, place a plate of the kind to be used half in the leaves of 

 a book, expose for (say) four minutes at the spot where the 

 operation of development is to be conducted, thereafter de- 

 velop the plate as much as possible in total darkness, and it 

 will be easy to discover if the light is unsafe, for, if it is un- 

 safe, the half that projected from the book will " take a tint," in 

 other words, will develop darker than the part which the book 

 protected. It is vastly important in photo-micrography to see 

 exactly what the plate does under development, but in order to 

 examine the plate critically, no great space of time is necessary; 

 the rationale of the light question may therefore be summed 

 up : Use the greatest possible amount of safe light, but do 

 not waste any light ; that is, do not expose the plate to light, 

 however safe, when no object is gained by such exposure. 



Non-actinic lamps are held in stock by all photo dealers; we 

 figure one : 



FIG. 17. DARK ROOM LAMP. Carbutt. 



A wooden sink lined with sheet lead seems preferable to iron 

 or earthenware, and in the sink should be a wooden " hatch " 

 or grating on which measures, bottles, etc., may stand and 

 drip. On one side at least of the sink should be a ledge or 

 table sloping down to the sink and lined with lead or covered 

 with rubber or American cloth, so that dripping dishes, etc., 

 may be laid on the slope and their drippings run into the sink. 



