That every telegraph company or other corporation operating a telegraph line through or into the corporate limits of cities of the first class is hereby required to establish and maintain a telegraph station in each of said cities of the first class containing fifty thousand inhabitants or over, with the usual facilities and appointments for the convenience of the inhabitants of said cities, during the hours from eight o’clock in the forenoon until twelve o’clock midnight of each day, and deliver messages to the inhabitants thereof at all such hours free of extra charge therefor.