CONCERNING LAWNS 349 
to penetrate beneath the stone and cement floor 
after it had been buried so deep in the ground, 
and when they had, and had enjoyed for over a 
thousand years at the least, a soil formed of 
vegetable mould as deep as earthworms require to 
live and flourish in? A depth of three or four feet 
of mould is as much as they require, but they will, 
Darwin says, occasionally go deeper to five or six 
feet, and he gives nine feet as the greatest depth 
at which they have been found. Now at Silchester 
I saw some taken from a depth of twenty-five feet, 
and very many at eighteen to twenty feet. This 
was when the old Roman wells and other deep 
pits were cleaned out. 
It struck me that these Silchester observations 
made a valuable contribution to a history of the 
earthworm’s life habits. For it should be borne 
in mind that the soil covering the buried city is a 
rich mould, which has been under cultivation for 
the last nine or ten centuries, and is the kind of 
soil in which the earthworm finds his best con- 
ditions and attains his greatest size and vigour. 
Consider next that the soil in the deep pits and 
everywhere beneath the Roman pavements is a 
cold, heavy, hardly-pressed earth undisturbed for 
many centuries, unpierced by root of plant or ray 
of sun, and probably to a great extent devoid of 
the microbic life which makes the upper soil alive. 
When you turn over this long-buried soil with the 
spade it has a heavy damp smell, but not the 
familiar earth-smell of Clodothrix odorifera. Yet 
