29. Derivation of agent's authority.

As has been previously stated1, the authority of the agent may be derived expressly from an instrument, either a deed or simply in writing, or may be conferred orally. Authority may also be implied from the conduct of the parties or from the nature of the employment2. It may in certain cases be due to the necessity of circumstances3, and in others be conferred by a valid ratification subsequent to the actual performance4