The master of every workhouse shall keep an exact account of the time of the commitment and discharge of prisoners, their maintenance, the articles and materials provided for them to work, and the earnings and proceeds of their labor, and report the same to the board of chosen freeholders at its annual meeting and at other times when required. He shall pay over to the county treasurer the amount of such earnings and proceeds at the time of exhibiting his accounts, which moneys shall be appropriated to the uses of the county.