1883.) Fresh News on Earthworms. 89 
vegetable matter thus swallowed will of course be utilised 
as nourishment. 
As regards the horizontal subsidence of stones, rocks, &c., 
Muller does not, like Darwin, find the phenomenon satisfac- 
torily accounted for by the removal of the earth from be- 
neath by worms, and its gradual accumulation around their 
sides. Here his observations are completely in accord with 
those of Mr. Kinahan as laid down in our last year’s volume 
(p. 377). It does indeed seem that in this respe( 5 t Darwin 
has somewhat overlooked other agencies. To one of these, 
so familiar as to be forgotten, we must beg for a moment to 
diredt attention. Everyone must have noticed how on a 
frosty morning — especially if there has been previously much 
wet weather — pebbles, fragments of stone, & c., which have 
been imbedded in the ground, appear to have sunk down 
below the surface. This is to be noticed even in compadt 
gravel-walks where worms are entirely absent. The reason 
of this is plain : the water held by capillary attraction within 
the pores of the stone expands on freezing, and thrusts the 
loose soil upwards. When a thaw succeeds, the soil or 
gravel falls back to some extent into its old position, but not 
entirely so ; the edges of the stone after each such alterna- 
tion are more and more covered, until at last it disappears 
from sight. Something of the same nature will take place, 
to a slight degree. 
Another agency which must probably contribute to the 
subsidence of stones, and even to their translatory movement 
on the slope of a hill, must be sought in the expansions and 
contractions which are known to take place in the earth’s 
crust in accordance with changes of temperature and baro- 
metric pressure, and in those slight vibratory movements 
which are far from uncommon. It is well known that if we 
mix together in a box fragments of stone, &c., with sand or 
other similar powder, and set the box aside in what we think 
a quiet place, in the lapse of years these different materials 
will sort themselves out, the larger fragments finding their 
way to the bottom. This process is constantly going on in 
Nature, as far at least as regards stones resting on arable 
soil, loose sands, gravels, and peat earth. Mr. Kinahan, in 
the article referred to, makes mention of a number of other 
agencies which are undeniably concerned in the result. 
Hence without seeking to deny that worms take a part, and 
occasionally a prominent part, in the subsidence and dis- 
placement of stones, we submit that a complication of causes 
is here concerned. 
VOL. v. (third series.) 
h 
