containing tools may be surface gravels on a plateau; note then the
level, and the relation of them to any cliffs; do they end abruptly
at a cliff edge, showing that the valley was filled up; or do they
fade away to the edge, showing that they are older than the valley
erosion? Gravels may be the filling up of a valley which was
previously eroded; note the highest level at which they can be
traced; often little pockets of deposit, or traces of sandy strata,
can be found clinging high up on cliffs; also note the depths in the
gravel at which any tools are found. Any shells or bones in the
gravels are of the greatest value; the depth at which they are found
should be written on them at once, with the locality.

Surface flints
should have levels noted on them. If sharp they show that probably
submergence has not reached that level since; if worn, then water has
been up to a higher level, from which they have been washed down.

Levelling
may be read from a contour map, if there is such available. In most
countries it must be done by reading feet on an aneroid barometer,
set with zero of level scale to 30 ins. or 760 mm. Then visit as soon
as possible some point where a level is marked on the map, as a hill
top, and read the barometer. This will give the correction to be made
to all the previous notes. If there is no level recorded, get down to
a stream bed (the larger the better) and read it there, recording the
exact place on the map. The level may then be worked out
approximately by points above and below on the stream, for accurate
reading, hold the aneroid face up, gently tap it, and read; then face
down similarly, and take the mean. Guard that the wind does not blow
against any keyhole in the case.