Any city council may provide, by resolution, for taking census or enumeration of the inhabitants thereof, and in such resolution shall provide for engaging the services of the bureau of census, U.S. department of commerce, to take said census or enumeration. Whenever it shall have been duly ascertained by any census or enumeration taken as hereinbefore provided, such fact shall thereupon by the clerk of said city, be certified to the secretary of state and to the county clerk wherein said city is situated. Provided further, that the population of any city determined by a special census shall thereafter be used in apportionment of state revenues in which the city may share.