The boundary between the high-density region and the deeper interior was not like the boundary between the standard Middle Domain and the high-density region.
The high-density region's threshold had been a clear line, the Law-matter on either side distinguishable by density, the crossing immediate and total. The deeper interior's boundary was a gradient, the density increasing over a stretch of ground that took the better part of a full cycle to traverse, the change present in each step rather than concentrated at a single crossing point.
He understood the difference.
