being cleaned, pass into
the coating rooms, N and O, into which daylight is never admitted; the
coating machine is in the room, N, and three hand coating tables in
the room, O; both these rooms are illuminated by non-actinic light.

[Illustration: Fig. 2.]

[Illustration: Fig. 3.]

The walls of N and O are of brick, to keep these interior rooms as
cool as possible in hot weather, for the making of photographic plates
is more difficult in summer time, because the high temperature tends
to prevent the rapid setting of the gelatine emulsion upon them. At
the end of these rooms and communicating with both is the lift, P, by
which the coated plates are carried to the drying rooms above, which
there cover the entire area of the main building; they consist of two
rooms measuring 60 ft. by 30 ft., and are each 30 ft. high at the
highest part in the center of the building; these rooms are
necessarily kept in absolute darkness, except while the plates are
being stored therein or removed therefrom, and on such occasions
non-actinic light is used. After the plates are dry, they come down
the lift, Q, into the cutting and packing room, R, which is
illuminated by non-actinic light. In the drying rooms the batches of
plates are placed one after the other on tram lines at one end of the
room, and are gradually pushed to the other end of the building, so
that the first batches coated are the first to be ready to be taken
off when dry, and to be sent down the lift, Q. The plates in R, when
sufficiently packed to be safe from the action of daylight, are passed
through specially constructed openings into the outside packing room,
S, where they are labeled. The chemicals are kept in the room, U,
where they are weighed and measured ready for the making of the
photographic emulsion in the room, U. The next room, V, is for washing
small experimental batches of emulsion, and W is the large washing
room. The emulsion is then taken into the passage, X, communicating
with the two coating rooms. A centrifugal machine in the room, Y, is
used for extracting silver residues from waste materials, also for
freeing the emulsion from all soluble salts. Washing and cleaning in
general go on in the room, Z.

[Illustration: Fig. 4.]

The glass for machine coating is cut to standard sizes at the
starting, instead of being coated in large sheets and cut afterward--a
practice somewhat common in this industry. The disadvantage of the
ordinary plan is that