Section 7. The clerks of the courts may designate such employees in their offices, as in their judgment may be necessary for the convenience of the public, as deputy assistant clerks of the courts, who shall have the same authority to administer oaths as the assistant clerks of the courts. Under the direction of the clerk, such of his duties as clerk of the county commissioners as he shall designate shall be performed by a deputy assistant clerk. The clerks of the courts may from time to time, as necessity or the public convenience requires, authorize in writing one or more deputy assistant clerks, designated as aforesaid, to act as assistant clerks of the courts and may in like manner invest them with such powers of assistant clerks as may be necessary for the purpose.