The naval spy works in a somewhat similar manner to his military colleague. At every naval port in Great Britain it is quite safe to assume that there are spies actively carrying on their work, though it is quite true that one or two, who have long been under suspicion, have now found it wise to disappear into oblivion. A favourite guise of the spy in a naval port is, it seems, to pose as a hairdresser, for in pursuance of that humble and most honourable calling, the secret agent has many opportunities to chat with his customers, and thus learn a good deal of what is in progress in both port and dockyard: what ships are putting to sea, and the strength and dispositions of various divisions of our navy. Cases in recent years of spies at Portsmouth, Chatham, and Plymouth have revealed how active Germany has been in this direction. In one case, at Plymouth, a salary of £500 a year was offered to a Mr. Duff for information regarding naval matters, on the pretext that this information was required by a Naval and Military journal in Germany. Mr. Duff, however, communicated with the authorities, who promptly arrested the spy--a man named Schulz, who lived on a yacht on the river Yealm. He was tried at the Devon Assizes and, certain documents being found upon him, he was sentenced to a year and nine months' imprisonment. What, we wonder, would have been his fate if he had been British, and had been arrested in Germany? Of diplomatic espionage little need be said in these pages. Every nation has its secret service in diplomacy, a service rendered necessary perhaps by the diplomatic juggling of unscrupulous representatives of various nations. Many diplomatic spies are women moving in the best society, and such persons abound in every capital in the world. The means of communication between the spy and his employers are several. Innocent sketches may be made of woodland scenery, with a picturesque windmill and cottage in the foreground, and woods in the distance. Yet this, when decoded in Berlin--the old windmill representing a lighthouse, the trees a distant town, and so forth--will be found to be an elaborate plan of a harbour showing the disposition of the mines in its channel! Again, there are codes in dozens of different forms of letters or figures with various combinations, key-numbers, cross-readings, etc. There is the three-figure code, the five-figure code, and so on, all of which, though difficult, can, if sufficient time be spent upon them, be eventually deciphered by those accustomed to dealing with such problems. Far more difficult to decipher, however, are communications written as perfectly innocent ordinary correspondence upon trade or other matters, yet, by certain expressions, and by mentioning certain names, objects, or prices, they can be rightly read only by the person with whom those meanings have been prearranged.