Iron County register. [volume] (Ironton, Iron County, Mo.) 1867-1965, 1901-12-12
AND STONES.
Borrowings Of the S~quirmers
Upon Large BowIders.

The following account is given by
c. Dawson, in knowledge, of the sink
ing of large stones by earthworms'
borrowings: Horace Darwin com
menced an experiment 20 years ago.
A circular stone about Is inches in di-
ameter and 2A inches thick and
weighing about II pounds was laid
upon the ground in a level field near
Mr.. Darwin's house at Down, which
had probably been pasture for more
than so years, and under a large Span
ish chestnut tree. A hole was made
through its center and was lined with
a brass cylinder containing on the top
three horizontal projecting pieces
loaded into the upper surface of the
stone. In each of these pieces a radial
V-shaped groove was cut. To obtain
a Ike point from which the displace-
meuts of the stone were to be meas
ured, two rods, one of copper and the
other of iron, and each Sc of an incn
in diameter, were driven side by side
inte-the ground to the depth of about
So feet, and the ends were cut off so
that they stood at first about three
inches above the ground, OF not quite
gil litCn dDOtC III upDSI VI
the stone, which was placed with the
rods projecting through the central
hole. Movements of the stone were
produced by other agencies than the
burrowing of earth worms. Some,
put an unknown, displacement may
have been caused by the growth of
the roots of the chestnut tree, under
which the stone lay. But this, if it DC
Cured, must have been far less than
that due to frost and changes in the
dampness of the ground. The stone,
indeed, was found to be in a state of
continual vertical oscillation. When
the soil vas damp from recent rain,
one or two cans of water poured on
the ground near the stone made it
rise one-fiftieth of an inch in about
seven hours. During a severe frost
in the beginning of 1873, the stone rose
three-tenths of an inch, and, during
the thaw which followed a slight frost
a little later in the same year, it fell
nearly one-tenth of an mel in less
thar five hours, even though the
ground below was still hard.
Until the end of 1886, the position of
the stone was usually measured each
winter and summer, and during the
next ten years in the sumner only.
The curve obtained from the summer
measurements is more irregular than
from those made in winter, probably
on account of the greater variation in
the dampness of the soil in summer.
During the last nine years in which
the experiment was made (1SS7-1S96)
the total descent, given by summer
measurements, was less than one
eighth of an inch. 1t is difficult to
account completely for this very slow
rate, but, during part of the time the
rainfall was certainly above the av-
erage. In the earlier half of the
interval, however, the rate of descent
was much greater, though this may
have been partly due to the decaying
of the grass, for the stone was at
first placed directly on the turf. TAX
ing the winter readings, Horace Oar
win found that the stone sank seven
tenths of an inch in the eight years
from 1878 to 1886, or at the rate of
seven-eighthst of an inch in ten years.
This, as we might expect, is much less
than the rate at which worms cover
up small pebbles, put it is about twice
as great as that at which the large
stone examined by his father sank
into the ground.