Whenever in any county there shall have been raised by subscription a sum of money not less than $100.00 for the establishment of a library of pedagogical books for the use of the teachers of the public schools, the director of the treasury shall, upon the order of the commissioner, draw his warrant on the state treasurer in favor of the county superintendent of the county for the sum of $100.00 for the benefit of such library. Annually thereafter there shall be paid on a like order a sum not less than $50.00 nor more than $100.00 upon condition that there shall have been raised by subscription a like sum for the maintenance of the library for the year.