What about those millstones?

From the Queens Gazette:

The Dutch Kills millstones are to be installed in the traffic islands. [Dan] Colangione said the EDC has retained a historical resources consultant and, in collaboration with the city Parks Department, is producing a plaque that describes the millstones. The stones are currently at the branch of the Queens Borough Public Library on 21st Street and 38th Avenue while their final display is determined. Colangione said the idea of cutting dowels into the stones was abandoned after several protests that the process could immediately damage them or leave them vulnerable to later damage. Instead, they will be fixed to their pedestals by grouting. (That time and weathering might deteriorate the grouting was brought up at the meeting and determined to be an inevitable problem of maintenance.) Only old-fashioned hand tools are used on the stones, the EDC spokesman said, with no power tools being allowed.