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peculiar wind currents all tend to prove that this really was 
the case. In a few places near this point blue clay makes its 
appearance, and, I believe, it would be found under the 
yellow clay in most places if sufficiently deep sections were to 
be exposed. But in the valley of the Wharfe, the scattered 
yellow clay is often variegated, and might be mistaken for 
the true blue clay. In and around my garden the clay is 
bluish, but to which of the formations of boulder clay it 
really belongs I cannot positively say. It is full of boulders 
more or less rounded, some of them very large, and several 
of them glacially rubbed and striated. 
Between Ilkley and Arthington the yellow clay, some- 
times visibly underlain by the blue, often makes its 
appearance in the railway cuttings. It runs up the south 
slope of the Wharfe valley till it graduates into the angular 
detritus underlying the escarpment of Otley Chevin. (See 
fig. 3, plate I.) Between Burley and Guiseley there is much 
boulder clay, either in knolls or flat plateaux. At Guiseley 
Railway Station, about 450 feet above the sea, there is yellow 
clay, apparently running down into the blue clay, but the line 
of demarcation between the two is probably connected by a 
facing or slight down-washing. It contains boulder and 
smaller stones of Millstone Grit, Sandstone, and a small 
per centage of Limestone. The boulder clay here rises up 
nearly, if not quite, to the summit level of the watershed 
between the Wharfe and Aire valleys, and covers large areas 
where it is impossible it could have been distributed by 
fresh water. Westward, it graduates into the angular 
detritus and loam underlying the eastern escarpment of 
Eombold's Moor. 
Comparing all the varied phenomena, so well known to 
geologists, spread over the north-west of Yorkshire, I am 
constrained to agree with the general theory enunciated by 
Professor Phillips, that during the elevation of the strata the 
