Undersown grass sward.

Thom's last book for the OUP is little known but Newcastle Library have a copy. He systematically measured ring diameters, in cup and ring carvings, and plotted the diameters as a histogram (Fig 5.1). There are clusters at five, six, seven and nine MI. The problem is, in measuring the diameters of the holes in stones, that the holes aren't truly round, but they too seem to cluster around these lengths.