Sheriffs and clerks shall also have offices in any city containing a population of not less than 7,000, as ascertained by the preceding census taken under the authority of Congress or the Legislature in which the city hall is not less than 55 miles distant from the site of the county courthouse. Such offices shall be kept open for the transaction of business continuously every day, except Sundays and holidays, in the period during which a superior court is in session in the city.