OTHER CAUSES.
Figs. 209 to 213, kindly lent by the Im perial Dry Plate Co., Ltd., afford inter esting examples of the different effects produced by various errors of working. Fig. 209 shows a cloud of small spots run ning in a regular line or wave. This re sult is chiefly clue to the use of a stale developer. The solution should not be allowed to stand in the measure, nor should it be used for more than one plate, except in those eases where the nature of the developer allows of this being done. Another variety of spots, due to the rest ing of air-bubbles on the film, is illustra ted in Fig. 210. Fig. 211 shows white spots with small dark centres, due to minute portions of unfixed silver. The presence of these opaque spots is explained by the fact that the portion of film not reached by the developer has remained unsoftened, and so fixes more slowly, thus leaving tiny particles of unfixed silver in the middle of the spots. Figs. 212 and 213 show the re
sult of uneven application of the de veloper. The negatives have not been properly covered with one sweep, and the in full daylight. As an example of the first method may be mentioned the pre paration sold under the name of Coxin. The plate is taken from the slide and im mersed in this solution, under cover of a changing bag. The dish containing the plate and Coxin solution is then taken out, and placed on the bench. When the solu tion has been allowed sufficient time to stain the film, the plate is transferred quickly to the developer, which is placed ready in another dish. Development is carried out as usual, density being judged solution has acted on some parts of the negative sooner than on the others. To avoid this, a sufficient quantity of develo per should be used, and it should be flowed with a rapid sweep over the plate.