An excellent plan of indicating the telling letter or word is through the heading of the communication. “Sir” might signify that every third letter or word was to be taken; “Dear Sir” that every seventh; “My dear Sir” that every ninth was to be selected.

A system very early adopted, known as the “grille” was the use of pierced cards, through the holes of which the communication was written. The card was then removed, and the blank spaces filled up. As for example:

My dear X. (The) lines I now send you are forwarded by the kindness of the (bearer) who is a friend. (Is not) the message delivered yet (to) my brother? (Be) quick about it, for I have all along (trusted) that you would act with discretion and despatch. Yours ever, Z.

There were other and very complicated systems based on arithmetical calculations for the transposition of letters of the alphabet, illustrations of which would be very prolix and possibly not interesting.

At the close of the sixteenth century, when the Spaniards were endeavoring to establish relations between the scattered branches of their vast monarchy, which at that period embraced a large portion of Italy, the Lower Countries, the Philippines, and enormous districts in the New World, they needed some method to correspond with their agents. They accordingly invented a cipher, which they varied from time to time, in order to disconcert those who might attempt to pry into the mysteries of their correspondence. The cipher, composed of fifty signs, was of great value to them through all the troubles of the “League” and the wars then desolating Europe. Some of their despatches having been intercepted, Henry IV handed them over to a clever mathematician, Vieta, with the request that he would find the clue. He did so, and was able also to follow it as it varied, and France profited for two years by his discovery. The court of Spain, disconcerted at this, accused Vieta before the Roman court as a sorcerer and in league with the devil. This proceeding only gave rise to laughter and ridicule.

The manner in which the French took possession of the republic of Strasburg, during the reign of Louis XIV, while peace prevailed, is very interesting. At that time the city had acquired great privileges, it being a free town, and was governed as a republic.

In 1680, when M. de Louvois was the French Minister of War, he summoned before him one day a gentleman named De Chamilly, and gave him the following instructions: “Start this evening for Basel, in Switzerland; you will reach it in three days; on the fourth, punctually at two o’clock, station yourself on the bridge over the Rhine, with a portfolio, ink, and a pen. Watch all that takes place, and make a memorandum of everything in particular. Continue doing so for two hours; have a carriage and post-horses awaiting you; and at four precisely, mount and travel night and day till you reach Paris. On the instant of your arrival, hasten to me with your notes.”

De Chamilly obeyed; he reached Basel, and on the day and at the hour appointed stationed himself, pen in hand, on the bridge. Presently a market-cart drove by, then an old woman with a basket of fruit passed; anon a little urchin trundled his hoop by; next an old gentleman in blue top-coat jogged past on his gray mare. Three o’clock chimed from the cathedral tower. Just at the last stroke, a tall fellow in yellow waistcoat and breeches sauntered up, went to the middle of the bridge, lounged over, and looked at the water; then he took a step back and struck three hearty blows on the footway with his staff. Down went every detail in De Chamilly’s book. At last the hour of release sounded, and he jumped into his carriage. Shortly before midnight, after two days of ceaseless traveling, De Chamilly presented himself before the minister, feeling rather ashamed at having such trifles to report. M. de Louvois took the portfolio with eagerness and glanced over the notes. As his eye caught the mention of the yellow-breeched man, a gleam of joy flashed across his countenance. He rushed to the king, roused him from sleep, spoke in private with him for a few moments, and then hastily despatched four couriers who had been in readiness since five o’clock on the preceding evening. Eight days after, the town of Strasburg was entirely surrounded by French troops, and summoned to surrender; it capitulated and threw open its gates on the thirtieth of September, 1681. Evidently the three strokes of the stick given by the fellow in yellow costume, at an appointed hour, were the signals of the success of an intrigue concerted between M. de Louvois and the magistrates of Strasburg, and the man who executed this mission was as ignorant of the motive as was M. de Chamilly of the motive of his. This unjustifiable action of France received formal recognition at the Peace of Ryswick in 1697, and she continued to hold the place until it was wrested from her by the Germans during the late Franco-German War.

The mysterious cards employed by the Count de Vergennes, who was Minister for Foreign Affairs under Louis XVI, in his relations with the diplomatic agents of France, exhibit great ingenuity in their arrangement and show what the political condition of Europe must have been at that time to require such precautions. The count was a great friend of America, and it was largely through his influence that the treaties of amity and commerce and alliance of 1778 were concluded. These cards were used in letters of recommendation or passports which were given to strangers about to enter or depart from France; they were intended to furnish information without the knowledge of the bearers. This was the system. The cards given to a man contained only a few words, such as,

Alphonse D’Angeha