"Nothing now," answered Marsh, "but you had better have several men where we can reach them in a hurry. How is Oak Street?"
"No change," was the reply. "Hasn't left the house all day." With that the man opened the door and left.
Marsh opened the envelope. It contained the black leather notebook, a letter, and some typewritten sheets. He sat down and read the letter.
The solution of the cipher code used in the notebook submitted, was comparatively simple and we were able to work it out here. This code was evidently not intended for the transmission of secret messages; it was very probably used exclusively to make notations in this book with the sole idea of maintaining privacy for these memoranda.
Due to the simplicity of the code, it could be easily memorized and therefore used for making hurried notes for quick reference.
To the inexpert person the combination of letters and figures gave a bewildering appearance to the notes, but it did not actually make the cipher any more intricate.
You can readily make up your own key to this cipher by writing out the letters of the alphabet from A to Z. Under these letters you again write the letters of the alphabet, placing the letter A under the letter Z and working backward. By this arrangement, A would stand for Z and Z for A. Below This you again write out the letters of the alphabet, and under these, beginning at Z and working backward, write the numbers 1 to 10, which brings you to the letter Q. From P to J you write the figures 20 to 26 and from I to A you write the figures 30 to 38. The person using this cipher probably memorized these two arrangements. In writing a word of say six letters, he would use four letters and two figures. To anyone glancing at his notes in a casual way, the system looked intricate, but to him these notes could be read almost as easily as if written in plain English.
Attached to the letter were several pages containing the decoded notations from the book. After carefully reading these, Marsh folded the sheets and started to place them in his pocket. Then he paused, glancing about the room thoughtfully. A moment later he smoothed the sheets out flat and lifting up the corner of the rug, slipped them under it well toward the center. Walking back and forth over the spot several times, he seemed satisfied. Then he turned up one of the chairs, placed the notebook inside of the bottom lining, and putting on his hat and coat, went out.