The work of road improvement shall be done under the general supervision and direction of the county engineer and he may appoint some competent person to act as inspector during the construction of such improvement. The person appointed as inspector shall receive, for each day actually employed at such work, a sum not to exceed four dollars, to be fixed by the engineer and paid out of any fund available for the construction of the improvement, upon the order of the board of township trustees with the approval of the engineer.