A still more remarkable instance is that of a German professor, Hermann, who boasted, in 1752, that he had discovered a cryptograph absolutely incapable of being deciphered, without the clue being given by him; and he defied all the savants and learned societies of Europe to discover the key. However, a French refugee, named Beguelin, managed after eight days’ study to read it. This cypher--though we have the rules upon which it is formed before us--is to us perfectly unintelligible. It is grounded on some changes of numbers and symbols; numbers vary, being at one time multiplied, at another added, and become so complicated that the letter _e_, which occurs nine times in the paragraph, is represented in eight different ways; _n_ is used eight times, and has seven various signs. Indeed the same letter is scarcely ever represented by the same figure; but this is not all: the character which appears in the place of _i_ takes that of _n_ shortly after; another symbol for _n_ stands also for _t_. How any man could have solved the mystery of this cypher is astonishing. Now let me recommend a far simpler system, and one which is very difficult of detection. It consists of a combination of numbers and letters. Both parties must be agreed on an arrangement such as that in the second line below, for on it all depends. 1 2 3 4 5 6 7 8 9 10 4 7 2 9 1 10 5 3 6 8 Now in turning a sentence such as “The army must retire” into cypher, you count the letters which make the sentence, and find that T is the first, H the second, E the third, A the fourth, R the fifth, and so on. Then look at the table. T is the first letter; 4 answers to 1; therefore write the fourth letter in the place of T; that is A instead of T. For _h_ the second, put the seventh, which is _y_; for E, take the second, _h_. The sentence will stand “Ayh utsr emma yhutsr.” It is all but impossible to discover this cypher. All these cryptographs consist in the exchange of numbers or characters for the real letters; but there are other methods quite as intricate, which dispense with them. The mysterious cards of the Count de Vergennes are an instance. De Vergennes was Minister of Foreign Affairs under Louis XVI., and he made use of cards of a peculiar nature in his relations with the diplomatic agents of France. These cards were used in letters of recommendation or passports which were given to strangers about to enter France; they were intended to furnish information without the knowledge of the bearers. This was the system. The card given to a man contained only a few words, such as: ALPHONSE D’ANGEHA. Recommandé à Monsieur le Comte de Vergennes, par le Marquis de Puysegur, Ambassadeur de France à la Cour de Lisbonne.