bances in
your calculations. Of course, if some one had deliberately made hay
with the lot, you would be nonplussed. The chances are, however, that,
given enough heaps of clothes, and bar intentional and systematic
wrecking of them, you would be able to make out pretty well which boy
preceded which; though you could hardly go on to say with any precision
whether Tom preceded Dick by half a minute or half an hour.

Such is the method of pre-history. It is called the stratigraphical
method, because it is based on the description of strata, or layers.

Let me give a simple example of how strata tell their own tale. It
is no very remarkable instance, but happens to be one that I have
examined for myself. They were digging out a place for a gas-holder
in a meadow in the town of St. Helier, Jersey, and carried their borings
down to bed rock at about thirty feet, which roughly coincides with
the present mean sea-level. The modern meadow-soil went down about
five feet. Then came a bed of moss-peat, one to three feet thick. There
had been a bog here at a time which, to judge by similar finds in other
places, was just before the beginning of the bronze-age. Underneath
the moss-peat came two or three feet of silt with sea-shells in it.
Clearly the island of Jersey underwent in those days some sort of
submergence. Below this stratum came a great peat-bed, five to seven
feet thick, with large tree-trunks in it, the remains of a fine forest
that must have needed more or less elevated land on which to grow.
In the peat was a weapon of polished stone, and at the bottom were
two pieces of pottery, one of them decorated with little pitted marks.
These fragments of evidence are enough to show that the foresters
belonged to the early neolithic period, as it is called. Next occurred
about four feet of silt with sea-shells, marking another advance of
the sea. Below that, again, was a mass, six to eight feet deep, of
the characteristic yellow clay with far-carried fragments of rock in
it that is associated with the great floods of the ice-age. The land
must have been above the reach of the tide for the glacial drift to
settle on it. Finally, three or four feet of blue clay resting
immediately on bed-rock were such as might be produced by the sea,
and thus probably betokened its presence at this level in the still
remoter past.

Here the strata are mostly geological. Man only comes in at one point.
I might have taken a far more striking cas