Each county officer or officers, for any district of a county shall at all times have free access to convicts in the custody of any official for the purpose of investigating their condition and treatment. The sheriff or his deputies shall visit the convict camp or county farms where the convicts of his county are kept or worked at least once in every month and more often if necessary. He shall make a thorough inspection and investigation of the treatment of convicts and report the same in writing to the board of supervisors. For failure to perform duty in this respect the board of supervisors may fine the sheriff Twenty-five Dollars ($25.00).