159. Identity of principal disclosed.

Where an agent in making a contract discloses both the existence and the name of a principal on whose behalf he purports to make it, the agent is not, as a general rule, liable on the contract to the other contracting party1, whether he had in fact authority to make it or not2; but a personal liability may be imposed upon him by the express terms of the contract3, by the ordinary course of business4, or by usage5, and he will be liable for breach of warranty of authority in cases where he had no authority