He turned his attention to the ruined doors of the inner room again, picking out minute pieces of débris from the lock with a pair of tiny forceps, and examining the pieces under the lens.
"I cannot be certain what explosive was used, Wigan, and the light here is bad. I will examine some of this dust at home," and he emptied the contents of the palm of his hand into a small envelope, which he folded up carefully and placed in an inner pocket.
Then he examined the floor of the outer room, and the passage without, picking up several bits of rubbish, but finding nothing of interest.
From the strong-rooms we went to the top of the building and examined the window and the roof. The window was at the end of a passage.
"Where do you suppose the thieves came from to get to this window?" Quarles asked, after he had examined it and the roof outside.
"The window yonder belongs to the adjoining block of offices," I said, pointing across the roofs. "It is quite easy to reach."
We started to go to it, but had only gone a little way when Quarles stopped.
"You may find it easy, Wigan, but my legs are not so young as they were, and climbing a roof is outside their business."
"At any rate, you can see that it is an easy journey," I said.
"Oh, yes, for young legs; and it is not likely this gang is composed of old crooks. By the way, I think they must have got out of this window as well as in at it. Look at this scratch on the sill—a boot heel, I should say, and the position would mean that the man was getting out. It is not certain that the stuff was not carried across the roof, Wigan. I wonder whether Mr. Bowman has returned to his office yet?"