LAMPLUGII : GLACL\L SECTIONS NEAR BRIDLIVGTON. 
289 
contents, if any, are preserved, to that in which all trace of its 
former condition is obliterated, and the substance is no longer 
distinguishable from the mass of the boulder-clay. These sections, 
indeed, present many examples of the boulder-clay in a state of 
arrested development, and in examining them we may follow the 
life-history, as it were, of that deposit. The raw material has 
clearly been most heterogeneous in character, and nothing has come 
amiss to the powerful engine which rolled out these clays. Sand, 
gravel or silt: clay, shale or solid rock; no matter of what age, whether 
old Secondaries scooped out of the North Sea floor, or ctuitem- 
poraneous moral nic matter only just laid down in front of the advancing 
sheet, all alike passed into the mixer and were more or less com- 
pletely reconstructed. 
So far all is clear enough, but when I try to conceive liow the 
soft shales and incoherent sand}^ beds came to be taken up from the 
sea bottom and transported, as most undoubtedly they have been, for 
long distances, difficulties arise, and I fail to reach a safe conclusion. 
Were the beds littoral, one might suppose that floating ice from the 
ice-foot assisted in the work by removing and carrying portions of the 
beach deposits to places in which they were afterwards overtaken and 
over-ridden by the steady forward-creeping land-ice ; but many of the 
shells indicate comparatively deep water, and may have come from 
almost anywhere in the bed of the southern part of the North Sea. 
Moreover, the evidence is distinctly in favour of the view that 
these incoherent masses became actually embedded in the ice, and 
rose with it to the higher levels, just as we know the solid boulders 
have sometimes done ; but how this was eff"ected I cannot make out, 
unless we may imagine that ' anchor-ice ' had formed and affixed 
itself to the sea bottom before the encroachment of the land-ice, with 
which it afterwards combined. But however the removal of the beds 
came about, the strong presumption that they were in some way 
or other actually embedded in the ice-sheet is a point which must 
not be lost sight of in studying the glacial gravels. These must 
ha\ e been derived in great part from the ablation of the ice, and 
if the ice contained marine shells we may be sure that traces 
of such shells would be found in the gravel formed from it, though 
laid down by fresh water at elevations far above sea-level. 
