310 
KENDALL I THE GLACIATION OF YORKSHIRE. 
sea, and down almost to Spurn Point. Beyond this it has never been 
found. Now besides this, which we may call the natural flow, inas- 
much as it follows the existing line of drainage as far as the sea, 
there is an inland distribution which crosses one of the most 
important though one of the least elevated watersheds in the 
county, viz.: that which separates the Tees drainage from that 
of the Ouse. The precise point at which the southerly flow 
commenced has not been determined, but down the central and 
eastern portion of the Vale of York Shap erratics are found in 
some abundance, and continue as far as the City of York, where 
considerable numbers have been found from time to time. The maps 
of the Geological Survey mark in the neighbourhood of York a series 
of features without compare in the whole of the British Isles, and the 
fact that the surveyors made no attempt in the explanatory memoir 
to point out their significance is, I think, probably to be ascribed 
to a desire to do fuller justice to them in a general treatise upon 
the Drift Geology of Yorkshire, rather than to any inability to 
interpret them. Be the cause what it may, it was reserved to the 
late Professor Carvill Lewis to acquaint the world with the fact that 
York was built in the centre of a magnificent crescentic terminal 
moraine, one of whose horns rested upon the oolitic hills about 
Barton Hill, while the other merged in a confused congeries 
of drift hills to the west of the city. This he correctly pronounced 
to be the terminal moraine of the Teesdale glacier. 
My own observations at York and in the neighbourhood show 
that this is not the only terminal moraine in the district. About five 
miles southward a second magnificent cresjent sweeps round in almost 
precise parallelism with the first, and has an arc of about the same 
chord and radius. I do not for one instant doubt the accuracy of 
Lewis's determination of the first to be a terminal moraine, and 
exactly the same reasoning applies to the second. Each is a long 
crescentic ridge or series of knolls, rising to a height in some parts 
of 70 or 80 feet about the surrounding dead-level of "warp" 
clays, sands, or gravels. The ridges are mapped by the Geological 
Surveyors as boulder-clay, sand, and gravel, and sections show many 
of the characteristics of the moraines of great glaciers. Dr. Parsons 
