134 THE MATRIX OF THE SUFFOLK BOULDERCLAY. [May 1902, 
the phenomena should be considered as a whole, and not piecemeal. 
He would reiterate that all the facts converged to one conclusion, 
from which there was no escape—that the North-Sea basin had 
been filled with an ice-sheet. The details now brought forward by 
the Author could be as well explained by transportation of material 
from the north-east as from the north-west. 
Mr. Wuiraxker supported the Author’s contention as to the general 
westerly derivation of the materials of the Suffolk Boulder-Clay. 
He mentioned certain gravels in Norfolk which were largely com- 
posed of Secondary materials, evidently derived from the Secondary 
outcrops to the west of the valleys in which these gravels occurred. 
The Author had, after all, confined his remarks to a comparatively 
small district in Suffolk, and this very restriction seemed to lend 
additional force to his contention. 
Prof. Sornas remarked that the Author’s argument against a 
derivation from the north or east depended, not on the assumed absence 
of Secondary rocks in these directions, but upon the rarity of sand 
in the Boulder-Clay under consideration. This, however, might be 
explained in more than one way, and did not to his mind preclude 
the possibility of a northerly and easterly origin. It would be 
interesting to know whether such sand-grains as were present showed 
signs of wind-action. 
The Avrnor, in reply, remarked that most speakers seemed to 
have assumed the clays to be the work of a certain agent, and to have 
argued for sources of the materials on that assumption. He had 
preferred to investigate the direction of the source; if that were 
found, enquiry as to the agent would be assisted. Mr. Lamplugh 
thought that the Yorkshire cliff-clays had been pushed up from the 
sea-bed : then the Suffolk clays had not been thus pushed up, for the 
sandy matrix of the former was totally different from the fine tena- 
cious material of the latter. In regard to Prof. Sollas’s enquiry as to 
the wind-polished sand-grains, if present these still might have been 
derived out of other beds. He used the word ‘ western ’ in a general 
sense. 
