564 MR. P. F. KENDALL ON A SYSTEM OF [Aug. 1902 
mouth of the Tees would itself have been closed by the ice-sheet in 
the North Sea; but I think that the impact of the Scandinavian ice 
would have proceeded from north to south, and the Firth of Forth 
(being 100 miles to the northward of the Tees) would have ex- 
perienced its effects long before they reached the coast of Yorkshire. 
The Teesdale Glacier must have continued to discharge into the 
North Sea for a long period of time, for erratics of Shap Granite 
are very numerous in the Drift of Yorkshire. Messrs. Muff & 
Sheppard enumerated 89 of large size, all exposed at the same 
time, on the foreshore of Robin Hood’s Bay, in a distance of about 
3 miles. How far to seaward the glacier made its way I am 
unable to determine, though the ‘ Rough Ground,’ regarded by 
Carvill Lewis as its moraine, lies some miles from the coast (see 
p- 496), I am equally unable to decide how far down the coast 
it made its way when the ice-sheet deflected its flow to the 
southward, and to what altitude it attained along the northern 
front of the Cleveland Hills. ‘The dispersal of its characteristic 
erratics in horizontal and vertical extensions is of no assistance in 
determining this point, as the dispersal may have been accomplished— 
and I believe it was—largely by the redistributing action of the later 
ice-streams. 
It might be thought that the high altitude attained by the Lower 
Boulder-Clay mentioned in an earlier section would have been 
decisive, as that division of the Drift contaiis Shap Granite, but I 
have long felt that the classification of the Glacial deposits was in a 
very unsatisfactory condition. J am far from being convinced 
that the ‘ Lower Boulder-Clay’ of the high grounds is the same as 
that of low levels, for I find a most marked difference between the 
assemblage of erratics in the whole of the Drift observed by me at 
high altitudes, and that recorded as characterizing Lower Boulder- 
Clay at Whitby and Robin Hood’s Bay. Whereas at those two 
localities the recorded erratics belong almost exclusively to the 
western or Teesdale type, I have found a very remarkable deficiency 
of Carboniferous rocks at high elevations; while rocks of the 
northern group (see p. 491), such as Cheviot porphyrites, greywackes, 
sandstones, and the Roker Magnesian Limestone, are extremely 
common both in the Boulder-Clay and the Gravel. Scandinavian 
rocks are also occasionally to be found. My impression is that the 
differences between the ‘Upper Boulder-Clay’ and the ‘ Lower 
Boulder-Clay ’ are indicative more of local conditions than of age. 
I have not succeeded in establishing any correlation of the lake- 
phenomena with the period of prevalence of the Teesdale Glacier, 
nor can I expect to do so, for the evidences of lakes formed during 
the advance of the ice must in almost all cases be obliterated. 
The second phase of the glaciation of Cleveland was the complete 
diversion of the Tees ice into the Vale of York. ‘This was brought 
about by the growth of the Scandinavian ice-sheet, and the gradual 
and progressive obstruction of the British coasts from the Forth 
downward. Whether the Scandinavian ice ever directly impinged 
upon this part of the coastline of Yorkshire or not, I will not 
Beat ait 
