“We must not expose the plates too long even to this faint light,” the Doctor remarked, as he opened one of the plate-holders. Then he took out one of the plates and showed the boys that the plate was coated on one side with a yellowish substance; then, still keeping it in shadow, he let each of the boys feel both surfaces. The coated surface had a smooth feeling.
“The plain glass side feels sticky, doesn’t it?” said McConnell.
“In the dark,” said the Doctor, “you can easily tell the difference, though you should always feel the plates near the margin, because the moisture of the fingers may leave a stain that will afterward appear in the developed plate. My chum once photographed me sitting by the window, and a finger mark which fell on my face—that is to say, on which my face fell, for I think the carelessness was before the picture was taken—made me look like a very disreputable citizen indeed. My chum said I looked like a surprised pirate. Now, if you know how a surprised pirate looks, you can fancy my appearance. But usually you won’t need to feel the plates to place them properly, for each maker packs his plates in a certain way. This maker packs them face to face. That, I should judge, is the usual way, now. And here goes for the plate-holders.”
When the plate-holders each had their two plates in position, back to back, the Doctor said it would be well to remember that the four remaining plates in the package must not be confused with the others when the time came for developing or changing plates. But, he added, “I know well enough that you will have to make all these mistakes to know how to avoid them.”
“Did you do that with your prescriptions, father?” asked Allan, with a grin that was not concealed even by the half darkness.
What the Doctor might have answered it is hard to say, for just then Mrs. Hartel knocked at the door to say that Owen had come. In fact, Owen was then at the door.
“Come in,” called the Doctor, the plate-box being safely closed.
“Hello, Owen,” shouted Allan from behind the lantern. “I didn’t go after you because I thought it was your night at the Choral.”
“There wasn’t any meeting to-night,” Owen said, “and I just happened to hear from Cheney that you had a camera. What is it?”
“A Wizard,” said Allan, “and a little beauty. I wish it was daylight. I hate to wait until to-morrow.”