The results of these observations on the relation of limestone or
other alkaline soils to blight distribution, are as follows, which are
simply, however, what appear to be the facts obtained from studies to
date, and are not put forth as absolute conclusions.
(1)—In every series of tracts taken from limestone to overlying shale
soils, the percentage of blight is least at a comparatively short
distance (50 to 200 ft.), from the edge of the limestone.
(2)—Tracts on soils derived from limestone which show the highest
percentage of blight seem to be those where the soil has become acid
from underground drainage, and consequent leaching out of the alkalies.
(3)—Chestnut trees on soils derived from other alkaline rocks show
less blight than is found in the trees on shale soils with limestone
underneath.
(4)—Where the rocks have been faulted, and an older crystalline rock
has been brought up to the level of the later formed limestone, there
does not appear to be any less blight on the crystalline rock near the
limestone.