The board of supervisors, at its July meeting, shall carefully examine the assessment roll, or rolls, returned by the tax assessor and shall then decide if a new assessment be necessary. If it be found that the assessor is incapable, or that his assessment is so imperfect that it ought not to be approved, even if objections be not filed, the board may appoint some suitable person to proceed immediately to make the assessment. The board of supervisors shall in such case adopt an order setting forth the true facts and conditions and the time necessary for making of a new assessment roll, or rolls, and shall certify the order to the Department of Revenue. The Department of Revenue shall, upon receipt of the certificate from the board of supervisors, determine and notify the board of supervisors when the roll, or rolls, shall be filed, the time for equalization by the board of supervisors, the giving of notice to taxpayers and the time when objections to the roll, or rolls, shall be heard and determined by the board of supervisors. The person appointed to make the assessment shall proceed immediately to make the assessment in the same manner and with the same powers of the tax assessor when assessments are made at the time provided by law, and shall prepare and file the assessment roll, or rolls, within the time prescribed by the order of the department. The person so appointed and discharging the duty shall be allowed the compensation allowed by law to the assessor for like services, and shall have the same deputies allowed by law to the tax assessor. The board of supervisors shall require of the persons appointed the same bond as is required of the tax assessor. The roll, or rolls, made under the provisions of this section shall be the legal assessment roll and the old one shall be thereby annulled.