e
sand becomes flooded and is no better than clay would be. A second
model will show this very well. Make a large saucer of clay and fill
with sand: {30} pour water on. The water stays in the sand, because it
cannot pass through the clay. A sandy field saturated like this will
therefore not be dry, but wet, and will not make a good position for a
house. We must therefore distinguish the two cases illustrated in Fig.
17. _A_ shows sand on a hill, dry because the water runs through until
it comes to clay or rock, when it stops and breaks out as a spring, a
tiny stream, or pond; this is a good building site and you may expect
to find large houses there. _B_ shows the sand in a basin of clay,
where the water cannot get away: here the cellars and downstairs rooms
are liable to be wet, and in a village the wells give impure water.
Matters could be improved if a way out were cut for the water, but then
the foundations of the buildings might move a little.

[Illustration: Fig. 16. Water bursting out from an underground spring,
Old Cateriag Quarry, Dunbar]

It often happens that villages are situated at the junction of sand and
clay, or chalk and clay, because the springs furnish forth a good water
supply.

On the other hand large tracts of clay which remain wet and sticky
during a good part of the year are not very attractive to live in, and
even near London they were the last to be populated: Hither Green in
the south-cast and the clay districts of the north-west have only of
late years been built on; while the sands and gravels of Highgate,
Chiswick, Brentford and other places had long been occupied.
Elsewhere, villages on the clay do not grow quickly unless there is
much manufacturing or mining; the parishes are large, the roads even
now are not good while they used to be very bad indeed. Macaulay tells
us that at the end of the seventeenth century in some parts of Kent and
Sussex "none but the strongest horses could in winter get through the
bog, in which at every step they sank {31} deep. The markets were
often inaccessible during several months. . . The wheeled carriages
were, in this district, generally pulled by oxen. When Prince George
of Denmark visited the stately mansion of Petworth in wet weather, he
was six hours in going nine miles; and it was necessary that a body of
sturdy hinds should be on each side of his coach to prop it up. Of the
carriages which conveyed his retinue several were upset and