38. Deviation.

It is a term of a contract of carriage that the carrier should carry the goods by his usual customary route1; and the carrier will be in breach where he deviates unnecessarily2 from that route3. A common carrier is not bound to carry by the shortest route but only by the route by which he usually carries and by which he professes to go4. In the case of a private carrier, the route to be followed must be determined by the terms of the contract, express or implied, and by the surrounding circumstances