PRACTICAL PHOTOMICROGRAPHY. 19 



equability of artificial light makes it a far more certain factor 

 in our work than ever daylight could be, even at its best and 

 steadiest. The fact that some magnificent work as of Drs. 

 Woodward, Maddox and others has been produced by daylight 

 only leads us to regret that these eminent workers had not the 

 advantages we have of equable radiants and very sensitive 

 plates. There are, however, over and above the actinic value 

 of daylight, certain qualities in daylight that make it, in spite 

 of its inferiority in some respects, invaluable if not essential 

 for certain kinds of work, and we do not wish to be taken as 

 despising or rejecting daylight entirely as our radiant. No 

 treatise on this subject would be complete without more than 

 a passing allusion to the use of natural light as the radiant, and 

 accordingly the subject shall be treated in such manner as is 

 within our power. 



Another advantage worthy of note, though always over- 

 looked, pertaining to basement apartments, is the equability 

 of temperature. The writer's half-basement operating rooms 

 do not vary 10 deg. Fahr. in the course of the entire year ; 

 never unbearably cold in winter they are a refreshing change 

 from the outside heat of summer. This is of more importance 

 to the advanced photo-micrographer than might appear ; the 

 microscopic apparatus keeps better and works better in such 

 conditions, and in such a room, in cold weather especially. The 

 heat arising from the radiant of whatever kind it be, pro- 

 duces much less serious effects on the apparatus, and much 

 less time is required for the parts to " settle " into their places. 

 (Seep. 173.) 



The above remarks are intended for those who propose to 

 enter seriously into the work of photo-micrography. Those 

 who propose only to work at odd times or on the easier sub- 

 jects, will not require such perfect preparations, or such per- 

 fectly adapted apartments ; it will be well, however, for every 

 intending worker to keep our hints in mind and to choose 

 apartments as nearly as possible fulfilling our desiderata. 



The purely photographic exigencies of the work may be 

 met either completely or partially according to the means and 

 intentions of the worker. Development of a micrographic 



