Sec. 1. The Commissioners Court of any county having a population of not less than 425,000 nor more than 500,000 may appoint a County Engineer, but the selection shall be controlled by considerations of skill and ability for the task. The engineer may be selected at any regular meeting of the commissioners court, or at any special meeting called for that purpose. The engineer selected shall be a Registered Professional Engineer in the State of Texas. The engineer shall hold his office for a period of two years, his term of office expiring concurrently with the terms of other county officers, and he may be removed at the pleasure of the commissioners court. The engineer shall receive a salary to be fixed by the commissioners court not to exceed the amount of the salary paid to the highest county official, to be paid out of the Road and Bridge Fund. The engineer, before entering upon the discharge of his duties, shall take the oath of office prescribed by law, and shall execute a bond in the sum of $15,000 with a good and sufficient surety or sureties thereon, payable to the county judge of the county and successors in office in trust, for the use and the benefit of the Road and Bridge Fund, of the county to be approved by the court, conditioned that such engineer will faithfully and efficiently discharge and perform all of the duties required of him by law and by the orders of said commissioners court and shall faithfully and honestly and in due time account for all of the money, property and materials placed in his custody.