GILLIGAN : ALLUVIAL DEPOSITS AT WOODLESFOKD, ETC. 267 
The slight discrepancy is due to the material sticking in the 
meshes and adhering to the sides of the sieve. 
The material which was greater than one-tenth inch consisted of 
pebbles of sandstone, clay ironstone, ganister, chert and grit, named 
in the order of their abundance. Separations of the heavy minerals 
with liquid of sp. gr. 2-8 yielded the following in order of relative 
abundance : — zircon, abundant in all separations, leucoxene, garnet, 
rutile, tourmaline, monazite, and anatase. 
These are of exactly the same type as those found in the Millstone 
Grit and Coal Measures. Whilst the list is not a long one, the actual 
amount of heavy minerals is rather large. As in the separations made 
from the Millstone Grit and Coal Measures almost the whole of the 
heavy minerals are found in the material which has passed through the 
90 mesh, and is less than -01 inch as actually measured with the mi- 
crometer. The exceptions to this in some of the separations were the 
garnets and lencoxene which were found in notable quantities in material 
of grade which passed the 60 mesh but did not pass the 90 mesh. 
Origin of the Deposits. 
In the description given of these deposits in the Memoir of the 
Yorkshire Coalfield (pp. 783 and 784), they are spoken of as rive^' 
gravels of considerable antiquity, formed when the stream was flowing 
at the level on which they now lie. But, as pointed out by Mr. 
Hawkesworth in the paper already cited, the problem cannot be so 
easily dismissed. In the Memoir, no mention is made of the laminated 
clay, which I first observed in 1909, and the first record of boulder 
clay at Rothwell Haigh was made by Messrs. Jowett and Muff in 1904. 
Mr. W. Lower Carter, in his paper on the Glaciation of the Don and 
Dearne Valleys, mentions these deposits at Rothwell Haigh and 
Oulton, and in supporting his idea of the existence of a glacier-like 
in Calderdale, writes* : — 
The northern edge of this lake {i.e., Lake Calderdale) would 
creep up to and over the watershed of the Calder and Aire at 
Lofthouse and Rothwell, would discharge its waters over the gap 
at Tingley into the Churwell valley and lapping round Middleton, 
would be bounded northward by the Airedale Glacier. This lake 
* Proc. Yorks. Geol. Sac, Vol. XV., Pt. III., p. 435. 
