As between principal and agent, an agent can be appointed only by a contract, which may be express,1 though informal, as by a statement by the principal that whatever the agent did "went2"; or implied3 as by acquiescence in the assumption of such authority by the agent.4 The chief rule as to form of appointment is that it must be of as high a nature as the act to be done by the agent. At Common Law the classes of contracts as to dignity were the formal and the simple, there being no distinction in rank between the oral and the written. Power to an agent to act under seal must be given by seal,5 unless he acts in the presence of his principal.6 So an agent cannot assign a tax certificate where an acknowledgment thereto is necessary.7 If the agent is to make a simple contract, any form of authority is sufficient unless there is some specific statutory provision to the contrary. Thus a contract which by the statute of frauds must be proved by writing, such as a contract to sell realty,8 may be made by an agent having oral authority. As between the principal and third persons, the facts may be such that the principal is estopped to deny the existence of an agency which is in fact non-existent, or to deny that it extends beyond its actual scope.9

1 Graves v. Horton, 38 Minn. 66; 35 N. W. 568; Hermann v. Ins. Co., 100 N. Y. 411; 53 Am. Rep. 197; 3 N. E. 341; Cribben v. Deal, 21 Or. 211; 28 Am. St. Rep. 746; 27 Pac. 1046; Bank v. Chester, 6 Humph. (Tenn.) 458; 44 Am. Dec. 318.

2 Scheibeck v. Van Derbeek, 122 Mich. 29; 80 X. W. 880.

3 Arnold v. Spurr, 130 Mass. 347; Matteson v. Blackmer, 46 Mich. 393; 9 N. W. 445; Reeves v. Kel-ley, 30 Mich. 132; Neibles v. Ry. Co., 37 Minn. 151; 33 N. W. 332; Cline v. Stradlee (Tenn. Ch. App.), 48 S. W. 272; Sheanon v. Ins. Co., 83 Wis. 507; 53 N. W. 878; Van Etta v. Evenson, 28 Wis. 33; 9 Am. Rep. 486. The statement is sometimes made that there is an agency of necessity. Benjamin v. Dock-ham, 134 Mass. 418. This is a figurative expression used to denote a liability which may arise without the consent and in defiance of the intention of the party liable.

4 Bank v. Mohr, 130 Cal. 268; 62 Pac. 511; Sammis v. Poole, 188 111. 396; 58 N. E. 934; affirming 89 111. App. 118.

5 Overman v. Atkinson, 102 Ga. 750; 29 S. E. 758; Watson v. Sherman, 84 111. 263; Jackson v. Murray, 5 T. B. Mon. (Ky.) 184; 17 Am. Dec. 53; Emerson v. Mfg. Co., 12 Mass. 237; 7 Am. Dec. 66; Wor-rall v. Munn, 5 N. Y. 229; 55 Am. Dec. 330; Smith v. Dickinson, 6 Humph. (Tenn.) 261; 44 Am. Dec. 306.

6 jansen v. Cahill, 22 Cal. 563; 83 Am. Dec. 84; Croy v. Busenbark, 72 Ind. 48; Gardner v. Gardner, 5 Cush. (Mass.) 483; 52 Am. Dec. 740.

7 Wilson v. Wood, 10 Okla. 279; 61 Pac. 1045.