The governor of the state of Idaho is authorized and empowered, upon the application of any railroad or steamboat company to appoint and commission during his pleasure any person designated by such company to serve at the expense of such company as policeman, with the powers of a police officer, and who, after being duly sworn, may act as such policeman upon the premises, cars or boats of such company. The company designating such person shall be responsible civilly for any abuse of his authority. Every such policeman shall, when on duty, wear in plain view a shield bearing the words, "railroad police" or "steamboat police," as the case may be, and the name of the company for which he is commissioned.