The board of supervisors of any county is authorized, in its discretion, to appropriate a sum not to exceed three thousand dollars per annum towards the support of public libraries, including circulating school libraries, in said county.
In counties where the enumeration of educable children is shown by the most recent census to be 10,000 or more, the board of supervisors may, in its discretion, appropriate an amount not to exceed ten thousand dollars annually, towards the support of public or school libraries.