De Chamilly obeyed; he reached Basle, and on the day and at the hour appointed, stationed himself, pen in hand, on the bridge. Presently a market-cart drives by; then an old woman with a basket of fruit passes; anon, a little urchin trundles his hoop by; next an old gentleman in blue top-coat jogs past on his gray mare. Three o’clock chimes from the cathedral tower. Just at the last stroke, a tall fellow in yellow waistcoat and breeches saunters up, goes to the middle of the bridge, lounges over, and looks at the water; then he takes a step back and strikes three hearty blows on the footway with his staff. Down goes every detail in De Chamilly’s book. At last the hour of release sounds, and he jumps into his carriage. Shortly before midnight, after two days of ceaseless travelling, De Chamilly presented himself before the minister, feeling rather ashamed at having such trifles to record. 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 four couriers who had been held in readiness since five on the preceding evening were despatched with haste. Eight days after, the town of Strasbourg was entirely surrounded by French troops, and summoned to surrender: it capitulated and threw open its gates on the 30th of September 1681. Evidently the three strokes of the stick given by the fellow in yellow costume, at an appointed hour, were the signal of the success of an intrigue concerted between M. de Louvois and the magistrates of Strasbourg, and the man who executed this mission was as ignorant of the motive as was M. de Chamilly of the motive of his. Now this is a specimen of the safest of all secret communications, but it can only be resorted to on certain rare occasions. When a lengthy despatch is required to be forwarded, and when such means as those given above are out of the question, some other method must be employed. Herodotus gives us a story to the point: it is found also, with variations, in Aulus Gellius. “Histiæus, when he was anxious to give Aristagoras orders to revolt, could find but one safe way, as the roads were guarded, of making his wishes known: which was by taking the trustiest of his slaves, shaving all the hair from off his head, and then pricking letters upon the skin, and waiting till the hair grew again. This accordingly he did; and as soon as ever the hair was grown, he despatched the man to Miletus, giving him no other message than this: ‘When thou art come to Miletus, bid Aristagoras shave thy head, and look thereon.’ Now the marks on the head were a command to revolt.”--Bk. v. 35. In this case no cypher was employed; we shall come, now, to the use of cyphers.