lamplugh: larger boulders of flamborough head. 233 
Per cent. 
3 Limestones, origin unproved, but two are probably 
Carboniferous, and the remaining one may be 
Silurian ... ... ... ... 27 
25 Sandstones and Grits, origin unproved, but all 
excepting one are suspected to be Carboniferous. 
The exception may be Jurassic ... ... 227 
6 Quartzite, conglomerates, etc., undoubtedly 
Primary ... ... ... ... 5'5 
41 Basaltic rocks ... ... ... ... 37 '3 
4 Gneissic, schistose and metamorpbic rocks ... 3*6 
3 Granitic rocks ... ... ... ... 27 
110 100-0 
Notes. — When compared with each other and with the list 
given in Part I., they are found to be ([uite consistent, and may, I 
think, be taken as yielding reliable indications of the proportion of 
the various rocks which form the larger boulders contained in the 
drifts in this locality. The only important variation is in the per- 
centage of sandstones, which is higher on the shore than in Danes 
Dyke Valley, while that of the basaltic rocks is decidedly lower ; 
especially in the first list, and this may be very readily explained by 
the action of the cartmen, who select the harder rocks for " road 
metal " but reject the sandstones. 
The most striking feature of the lists is the great preponder- 
ance of rocks from the Carboniferous and the all but total absence 
of Jurassic boulders of the- requisite size. Thus out of the 328 
erratics which the three lists contain not more than one can be 
identified with positive certainty as Jurassic. 
It must be remembered however that this refers only to the 
larger boulders, for a casual inspection of the smaller stones would 
almost everywhere reveal many Secondary pebbles. But, in my 
belief, it is to the larger, and especially to the angular and sub- 
angular blocks, that we should look for evidence as to the actual 
origin of the ice, for the smaller pebbles may never have been fixed 
in the mass of the ice at all, but may be merely beach-pebbles which 
the ice-sheet has worked into its basal-moraine as it passed 
