Out of a tube he dropped a single gem-like globule of cedar oil upon the blood smear; then he covered it with a small square of glass; upon this in its turn fell a second drop of the oil.
The whole was then placed in position under a microscope and fastened. Then the secret agent brought out the lens. It glittered like a tiny diamond in a huge setting, and Fuller gazed at it fascinated.
"How you can see anything through a glass as small as that I can't understand," said he. "It looks like the point of an awl."
"It is a one-twelfth objective," replied the other, as he screwed the lens firmly down upon the cover glass, and thus embedded it, so to speak, in the globule of cedar oil.
"It is necessary," said he, "that the specimen be observed through the oil because the lens must be brought down directly upon the glass; without the oil the glass would be scratched and the whole thing ruined."
Then he set himself to the close study of what the tiny lens made plain; in a few moments he lifted his head with an exclamation of triumph.
"What have you found?" asked Fuller eagerly.
"Evidence," answered Ashton-Kirk, triumphantly, "that will enable me to lay my hand upon the person who searched the library and clothing of Dr. Morse."
"But," demanded Fuller, "I don't quite understand."
Ashton-Kirk waved his hand toward the microscope, and Fuller applied his eye to it.
"What do you see?" asked the secret agent.
"A pale green circle," answered the other, "and it is crowded with irregularly shaped spots."
"Compare the circle with the dial of a watch and look closely at the point where the six should be."
"What do you see--at a very little distance from the edge?"
"There are some small blue spots; some are dark, the others lighter and more intense."
"That last is my proof," said Ashton-Kirk. Then as Fuller turned upon him a still inquiring look, he added:
"The indications have been that some member of Dr. Morse's household had a hand in his death. The house was secure at all points; it was not possible for any one to gain an entrance after the locking up. You might say: Suppose the criminal had entered the house before the time for locking up and remained concealed until he saw his opportunity? To that I would answer that we would have detected his method of departure. He should have left something unfastened behind him unless he had a confederate in the house. That the doors and windows, in every instance, were fast proves that this must be the case."