44 Cincinnatt Society of Natural Firstory. 
and those having ground glass stoppers are much the best. A 
passage-way having two doors about three feet or more apart lead- 
ing into the dark room is better than one door entering directly 
in, as the two effectually exclude white light, and permit the 
entrance or exit of any one without the necessity of turning down 
the light, one door closing before the other is opened. Should 
you be obliged to use a lantern in a dark room, let the shelf upon 
which your trays are placed be so large that you can move the 
light to each tray conveniently and not the trays to the light. If 
one can not have ventilating pipes, one or two slatted doors very 
similar to the outside shutters of houses, will allow considerable 
fresh air to enter, and practically exclude the light. Every weli- 
regulated dark room ought to be provided with a sponge, a scrub- 
brush and a cake of Sapolio. All trays and graduates should be 
kept clean and free from dust; a rubber funnel and a box of filter- 
ing paper is also very desirable to have. The window should be 
double, the outside of ground glass, and should slide up and 
down and not hang upon hinges. Personally I do not take 
much stock in ruby glass; ruby fabric and orange-colored 
paper used in conjunction give a much pleasanter light to 
work by, and are equally as effective in excluding the actinic 
rays. Label all your bottles; do not mix your developer 
until you are ready to use it; filter the old developer and 
keep it to use on over-timed plates, or to start development 
with when your exposure is doubtful. I have found it very con- 
venient sometimes to be able to distinguish my hypo trays from 
my developing trays without opening up my room to the light, 
and as I use the unglazed hard rubber trays, this is easily done by 
cutting a small notch on all four sides of my bypo trays, so that 
by simply running my finger along the edge I am unmistakably 
informed which tray I have in my hand. | 
Sometimes a fine camel’s-hair brush is used with which to dust 
off plates before putting them in the holders, but as this is stated 
to cause a slight electrical disturbance, whereby particles of dust 
are attracted to the plate, it may without detriment be dispensed 
with, and instead, the plates, after being placed in the holder, may 
be fanned with the slide before it is returned to the holder; this 
will remove as effectually any dust that might adhere to the films. 
Let me caution the younger members not to attempt to dry their 
plates by artificial heat. A plate that is perfectly dry can stand any 
