The board of supervisors of any county may, when in its opinion the interest of the county would be served thereby, have made a complete index of all chancery court causes and probate court causes which have been finally disposed of in the courts of the county. Said board may provide for the proper storage and preservation of the original papers in all cases which have been finally disposed of in the chancery court or the probate court of the county. Such general index shall be prepared by the chancery clerk, and the necessary filing system shall be installed under his direction. The board of supervisors shall be authorized to pay to the chancery clerk such reasonable compensation therefor as the board may deem proper.