quires a very soft brush and a careful hand to dust a
sensitive plate without scratching the film, and if the plate-holders
and camera-bellows are wiped frequently with a damp cloth there will be
little danger of pin-holes from dust spots in the sensitive plate.

Transparent spots in the negative are caused by air-bubbles forming on
the plate when the developer is turned over it, and the bubbles not
being broken, the developer does not have a chance to act on the film.

Larger spots on the plate or near the edge, which seem less intense than
the rest of the negative, are caused by the plate not being covered all
at once with the developer. The undeveloped plate should be placed in
the tray and the developing solution turned over it quickly with a sort
of sweeping motion, and the tray rocked in all directions till the plate
is completely covered.

Never place a negative in sunshine or near a stove to dry. The heat
causes the gelatine to melt and run off the plate. If for any reason one
wishes to dry a negative quickly, wash it, after removing it from the
hypo, for about half an hour, wipe off the water with a piece of damp
surgeon's cotton, lay the negative in the tray, and cover it with
alcohol. Let it remain in the alcohol for a minute or two, then take it
out and set it up to dry. It will dry in from five to ten minutes, ready
for printing.

Sometimes in warm weather the edges of the sensitive plate will come
loose from the glass. This is called "frilling," and occurs when the
developer is too warm. If the plate begins to frill, remove it to a dish
of cold water, and lower the temperature of the developer by setting it
for a few minutes in a dish of ice-water. The temperature of solutions
should not rise above 85 deg., or sink below 65 deg. if good results are
desired.

In a later paper full directions will be given for retouching negatives,
improving the high-lights, blocking out backgrounds, etc. But these
belong to the finer part of the mechanical work of photography.

SIR KNIGHT GLOVER BEARDSLEY, Auburn, New York, asks: 1, if one can
use a ruby light safely when putting a plate in the holder; 2, if
a plate should be left in the water after being taken from the
hypo, or if it can be washed off and put to dry at once; 3, in the
formula for making blue prints, where it says add one and one-half
ounce of citrate of iron and ammonium, if it means three-quarters
ounce each, and d