"Don't be too sure of that," smiled Chief Fleck, as he took the card.

"When you get used to codes, most of them identify themselves at the first glance--at least they tell what kind of a code it is. That's one thing about the Germans that makes their spy work clumsy at times. They are so methodical that they commit everything to writing. Now the most important things I know are right in here"--he tapped his head. "Every once in a while they ransack my rooms, but they never find anything worth while. Now this code"--he was studying the card intently--"seems to be one of a sort that our friends from Wilhelmstrasse are ridiculously fond of using. It is manifestly a book code."

"A book code," Jane repeated perplexedly. "I don't understand."

"It is very simple when two persons who wish to communicate with each other secretly both have a copy of some book they have agreed to use.

They write their message out and then go through the book locating the words of the message by page, line and word. That's what the three columns mean. Our only problem is to discover which is the book they both have. They often employ the Bible or a dictionary or--"

He stopped abruptly and studied the columns of figures.

"This code," he went on, "on its face is from a book that has at least 544 pages. One of the pages has at least 76 lines--that's the middle column--so the book must be set in small type."

"What book do you suppose it is?" asked Jane interestedly. She was glad now that she had listened to Carter. She was sure she was going to like being in the service. It was all so interesting, and she was learning so many fascinating things.

"If my theory is right those letters indicate that the book used was an almanac. That's the book that Wilhelmstrasse made use of when a wireless message was sent in cipher to the German ambassador directing him to warn Americans not to sail on the Lusitania. They betrayed themselves at the Embassy by sending out to buy a copy of this almanac. Let's see how our theory works out."

Taking up an almanac that lay on his desk he began turning to the pages indicated in the first column of figures, checking off the lines indicated in the second column and putting a ring around the words marked by the third column of figures.

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"Let's see--page 534--fifth line--second word--that's (eight). Now then--page 331--that's the chronology of the war in the almanac, so I guess we are on the right track--fifty-fourth line--sixth word--(transport)."