42 3Ir. Henry Walker's Lecture : 



patchy ; and at length it disappears where the sloi^e of the 

 valley begins, and here we meet the records of a later period 

 — records which did not begin until after this great sheet 

 of ice had disappeared in our south-eastern area of Britain. 

 The memorials of glacial Essex of which we thus get a 

 glimpse on the hill-tops and plateaux take us back to 

 the climate and time of the northern group of the Ilford 

 fossil mammalia. We have got back to the age of the 

 mammoth and woolly rhinoceros. It was a long enduring 

 age in Britain, and marked by many eventful and complex 

 phenomena. But we need only look at the later stage of 

 this incalculably long period, and witness, as it were, the 

 incoming of the more varied fauna with which we find 

 these northern animals associated in the fluviatile graves 

 of the Koding Valley. 



BEGINNINGS OF PLEISTOCENE ESSEX. 



At the time when the ice thus prevailed, the land — 

 except the summits of the most elevated districts, as the 

 Knockholt Downs, which as we look south from the Essex 

 heights appear projected on the sky-line — was for an untold 

 period of time lost to view beneath the sea. It suffered 

 the slow but sure spoliation and destruction of all vegetable 

 and animal life by that wonderful vicissitude the Great 

 Marine Submergence. Gradually sinking beneath the 

 waters, this part of the land-surface of Pliocene Britain, 

 with its forests and pastures, and all the varied animal life 

 of the period, its river courses and all terrestrial features, 

 became a sea-fioor. Here in this submarine condition it 

 was overlaid as the slow years went on with the sediment 

 and drifting waste of the sea, with the dropping debris 

 transported from land still above the waters, and with its 

 own looser rocks drifted to lower levels. 



As the land sank, and again as it emerged, pebble-beds 

 and gravels we see around us to-day were disturbed 

 and spread over wider areas, gathered in the submarine 

 valleys, and mingled with the mud and sand. The former 

 hills and plains of heath-clad Essex were wasted and 



