Termination of agent authority takes effect only when known to agent or to third persons, preserving prior acts. Termination of an agent's authority is not effective against the agent until it becomes known to him, nor effective against third persons until it becomes known to them; therefore acts by an agent or payments by third persons made in ignorance of a revocation or other termination remain binding on the principal, as illustrated by sales, payments, and post death transactions occurring before notice of termination.