131 
of Leeds, it exists only in patches. In the north-west part of 
the West RidiDg, where it lies near to, or on the carboniferous 
limestone, the stones and boulders in the blue clay are princi- 
pally limestone ; south-eastwards, the limestone pebbles and 
boulders decrease in number. Everj^where, but especially in 
the upland valleys, the stones are generally much rounded, 
polished, and scratched. 
2. Yellowish-hroicn and Variegated Boulder- Clay. — Though 
there are very few sufficiently- clear sections to warrant the 
conclusion, I believe that both the blue and yellow boulder- 
clays run imder the extensive beds of dark laminated clay 
and sand and gravel which spread out over the vale of York. 
One (if not both) of the boulder-clays has been found under 
the laminated clay and sand and stratified gravel of the vale 
of York. From low levels, the yellow clay extends up the 
valleys, and up the sides of the hills, until as a loam it thins 
out on the summits of the gritstone table-lands. The stones 
it contains are almost exclusively grit and sandstone at high 
levels, with a few limestone pebbles and boulders lower down, 
until at the bottom of the valleys, and on the plains, the per- 
centage of limestone is often considerable. On limestone 
rocks, the stones in the yellow clay are often nearly all lime- 
stone (as at Malham and Goredale), indicating a difference in 
the sources of supply for the clay and the stones. On and 
near the summits of the table-lands, the stones, with some 
striking exceptions, are angular or subangular; but they in- 
crease in bluntness and roundness downwards, until in many 
places they graduate into an un stratified boulder- gravel. 
The Rev. J. S. Tute, of Markington, informs me that the 
brown clay west of Ripon contains a few boulders of Shapfell 
granite. 
8. Boulder Sand and Stratified Gravel. — It is often difficult 
to discover a line of separation between the unstratified and 
stratified gravel. The unstratified gravel, generally speaking. 
