Yet, in spite of every precaution and all science and knowledge the country could bring to bear, news continued to leak through and to fly across the North Sea. Scotland Yard, to which admirable institution the whole world owes so much, was put upon its mettle. It proceeded to watch with still closer scrutiny certain suspected persons who still claimed the privilege of freedom. One of these was a small London tradesman whose premises were situated in a remote and quiet back street. He appeared to have rather more corresponding friends than his position or his business justified. His correspondence, in and out, was intercepted, copied, and sent along in a manner not likely to arouse his suspicions. Nothing, however, occurred which could be looked upon as even suspicious, until one day a telegram arrived which had been handed in at a certain naval base of some importance in the U.K. It simply said "Been ill three days--John," or words to that effect. Now the sender had also been watched, an attention which had been evenly divided amongst every one of this tradesman's correspondents. The police knew that the sender of the message, "John," had been in perfect health for quite a long time past, which fact was, of course, communicated to headquarters. The information caused a flutter in the official dovecots. Copies of the message, with comments, were forwarded to the War Office, to the Admiralty, and to other Government Departments likely to be interested. To shorten the story, certain gentlemen in the Admiralty were amazed when they remembered vividly that secret orders had been issued by them which commanded a squadron of warships to leave the port at which the message had been handed in, and join up with the High Seas Fleet _exactly three days_ from the date of the aforesaid message. Needless to add that the further activities of both the sender and the receiver of the telegram were forthwith promptly crushed, once and for all future time. Scotland Yard also discovered, probably with considerable assistance from the Censorship Department, that the Germans were successfully getting out information useful to them through open business letters addressed to residents in neutral countries, particularly Norway, Sweden, Denmark, and Holland, which were decoded by adding certain geometrical figures. For example, where the sides of an added triangle or triangles intersected one another, or cut the rim of a circle, there would be found the words used in the secret messages. Several of these ingenious codes were described in a most interesting article which was published in _Pearson's Magazine_, October, 1918, with illustrations which more clearly demonstrated their latent meaning. Two of the most brilliant of them were the knot alphabet and the chess problem.