LETTRE circulaire, Fr. a circular letter.
Lettre de cachet, Fr. an infamous state paper, which existed before the French revolution, differing in this essential point from an order of the British privy council, that the former was sealed, and the person upon whom it was served, carried into confinement without even seeing the authority by which he was hurried off in so peremptory a manner, or being tried afterwards for any specific offence; whereas the latter is an open warrant, which, (except when peculiar circumstances occasions a suspension of the habeas corpus act,) has its object closely investigated before a jury. The French lettre de cachet was written by the king, countersigned by one of his principal secretaries of state, and sealed with the royal signet.
Lettres de service, Fr. See [Letters] of service.
Lettres de passe, Fr. a paper signed by the kings of France, authorizing an officer to exchange from one regiment into another.
Lettre de créance, ou qui porte crêance, Fr. A letter of credit. It likewise signifies the credentials which an ambassador presents from his government to a foreign court.
Lettre de récréance, Fr. a letter which an ambassador receives from his government, by which he is recalled from a foreign court.
Lettres en chiffre, Fr. Cyphers. Baron Espagnac in the continuation of his Essai sur l’operation de la guerre, tom. 1, page 269, gives the following instructions relative to this acquirement. He observes that writing in cypher may be practised in two different ways. First by means of distilled vinegar, which is boiled with silver litharge, one ounce of the latter to a pint of the former. When this mixture has stood some time, it must be carefully poured off from the sediment, and it will appear as clear as rock water. Intelligence or information may be conveyed by writing with this water in the blank spaces of an ordinary letter, on wrapping paper, or on the blank leaves of a book. The instant the writing dries, not the least trace appears of what has been marked. To render the writing legible, you must make use of a water in which quick lime has been dissolved with a mixture of orpiment. This water is as clear as rock water; and if you steep a sheet of paper in it, and lay it upon the letter, book, &c. on which any thing has been written, the different characters will instantly appear.
The first of these distilled liquids is so powerful and searching, that by putting the written letter upon several other sheets of paper, after having rubbed the top sheet with the second water, the writing will be clearly seen in almost all of them. The same circumstance will occur, if you rub the leaf of a book or any piece of paper which you may spread upon it. These waters, especially the last, should be kept in bottles that are well corked up, to prevent the spirituous particles from evaporating. A fresh composition must, indeed, be made, if the old one should seem weakened. The letters that are written must likewise be carefully penned, and kept free from blots, &c. The paper must not be turned, nor rubbed with the hand until the writing be thoroughly dry. This is the author’s first proposed mode of writing in cyphers, the second may be seen in page 270 of the work already quoted.
Lettres de représailles, Fr. Reprisals. See [Letters of marque].
Lettres de santé, patentes de santé, Fr. letters of health.