All work performed by any such prisoners shall be performed under the direction of the highway commissioner of the township or the authorities of the city, village or institution where the work is done. All such prisoners while engaged in such work shall be under the control and custody of the sheriff. All tools necessary for use by such prisoners and all materials upon which work is to be performed shall be furnished by the township, city, village or institution in which the work is done. The sheriff shall take such precautionary measures as may be deemed necessary to prevent the escape of prisoners employed under the provisions of this act, and in case any prisoner employed shall escape, it shall be deemed to be an escape from the jail: Provided, That no additional deputy sheriff shall be appointed to guard such prisoners while so at work without the previous authorization of the board of supervisors. The board of supervisors is hereby vested with authority to reimburse the sheriff for any expenses incurred in conveying such prisoners to and from any such road, street, alley, highway, quarry, pit, yard, or institution or in properly guarding them while beyond the confines of the county jail: Provided, That all meals and food shall be furnished by the sheriff to such prisoners in the same manner as though they were confined in the county jail, except in cases where such prisoners are employed in or for a county institution providing board for inmates, in which case all meals and food shall be furnished by said institution: Provided further, That the board of supervisors shall have authority to provide for keeping such prisoners at places other than the county jail while they are performing such work as is authorized under the provisions of this act.