LETTER OF ATTORNEY, practice. A written instrument under seal, by which one or more persons, called the constituents, authorize one or more other persons called the attorneys, to do some lawful act by the latter, for or instead, and in the place of the former. 1 Moody, Cr. Cas. 52, 70.

2. The authority given in the lettor of attorney is either general, as to transact all the business of the constituent; or special, as to do some special business, particularly named; as, to collect a debt.

3. It is revocable or irrevocable; the former when no interest is conveyed to the attorney, or some other person. It is irrevocable when the constituent conveys a right to the attorney in the matter which is the subject of it; as, when it is given as part security. 2 Esp. R. 565. Civil Code of Lo: art. 2954 to 2970.