Owen shook the tray as if to dislodge something from the plate. “Why, there are several of them!” he cried. “They must be the windows of the factory!”
“Hooray!” shouted McConnell.
“Black windows?” asked Edith, perplexed.
“It is the fire,” said the doctor. “Light objects make a black image on the plate. That is why they can print from the negative. Daguerre made a positive—a natural image—on a metal plate which could not be duplicated. That was a daguerreotype. The English inventor of photography made negatives first on paper and then on glass. These could be used for making any number of positives or prints.”
“I see,” said Edith, her eyes on the plate. “Is anything more coming, Owen?”
“Yes,” said McConnell, “more little spots, and they are getting blacker. I think I see some flames shooting up.”
But Owen did not seem very sanguine. “It doesn’t seem to come out very well,” he mused. “I guess this one is the snap-shot.”
“Then there will be more on the two others!” cried Allan, hopefully.
They all were greatly interested to think that the other plates might have more on them. Owen’s guess proved quite correct. The other plates from the same holder came up in a much shorter time.
“Why, yes!” Edith exclaimed. “You can see the window-sash plainly, and the fire is spreading in this one.”