"Well, you see, Craig," I explained, "you put the top mirror through the transom of a door and—"
Kennedy interrupted with a hearty burst of laughter. "But suppose the door has no transom?" he asked, pointing to our own door.
I scratched my head, thoughtfully. I had assumed that the door would have a transom. A moment later, Craig went to the cabinet and drew out a tube about as big around as a putty blower and as long.
"Now, here's what I call my detectascope," he remarked. "None of your mirrors for me."
"I know," I said somewhat nettled, "but what can you see through that putty blower? A key hole is just as good."
"Do you realize how little you can really see through a key hole?" he replied confidently. "Try it over there."
I did and to tell the truth I could see merely a little part of the hall. Then Kennedy inserted the detectascope.
"Look through that," he directed.
I put my eye to the eye-piece and gazed through the bulging lens of the other end. I could see almost the whole hall.
"That," he explained, "is what is known as a fish-eye lens—a lens that looks through an angle of some 180 degrees, almost twice that of the widest angle lens I know of."