Prom Nottinghamshire the limits of the drift of the East
Anglian Glacier seem to run in a direction nearly due
west to east, for the great oolitic escarpment upon which
Lincoln Cathedral is built is absolutely driftless to the
northward of the breach about Sleaford. However, along
the western flank of the oolitic range true boulder-clay
occurs, bordering and doubtless underlying the great fen-
tract of mid-Lincolnshire; and the great Lincolnshire



ANCIENT GLACIERS IN EASTERN HEMISPHERE. 159 ■

Wolds appear to have been completely whelmed beneath
the ice.
" The most remarkable of the deposits in this area is
the Great Chalky Boulder-Clay, which consists of clay con-
taining much ground-up chalk, and literally packed with
well-striated boulders of chalk of all sizes, from minute
pebbles up to blocks a foot or more in diameter. Associ-
ated with them are boulders of various foreign rocks, and
many flints in a remarkably fresh condition, and still re-
taining the characteristic white coat, except where par-
tially removed by glacial attrition.
" One of the perplexing features of the glacial phenom-
ena in the eastern counties of England is the extension
of true chalky boulder-clay to the north London heights
at Pinchley and elsewhere ; for only the faintest traces are
to be found in the gravel deposits of the Thames Valley
of any wash from such a deposit, or from a glacier carry-
ing such materials.
" It has been suggested that the deposit may have been
laid down in an extra-morainic lake, or in an extension of
the North Sea, but these suggestions leave the difficulty
just where it was. If a lake or sea could exist without
shores, a glacier-stream might equally dispense with banks.
