Acts of servant of contractor.

When a public ferry has been duly leased or farmed out, every servant of the lessee, contractor or farmer shall be deemed to be legally bound to do everything necessary for or conducive to the safety of the public which he shall be required to do by any regulation made by the lessee, contractor or farmer and approved by the Commissioner and of which regulation such servant shall have had notice, and every such servant shall be deemed to be legally prohibited from doing every act which shall be likely to cause danger, and which by any such regulation he shall be prohibited from doing,