GILLIGAN : ALLUVIAL DEPOSITS AT WOODLESFORD, ETC. 
259 
The height of the solid rock at the north-west end of the excavation, 
where no alluvium is found, is 71 above O.D., and at the engine house, 
44 ft. above O.D., which gives a fall of 27 ft. in about a quarter of a 
mile. The upper laminated clay can be traced from end to end of the 
site, but the lower laminated clay commences a little north-west of 
where the shafts are situated, and is found right to the south-east end 
of the excavations. The presumption is that it continues still further 
to the south-east. 
PETROLOGY OF THE DEPOSITS. 
Gravels. 
The pebbles of Coal Measure sandstone and grit were very variable 
in size, the largest being about 6x3x2 ins. of Coal Measure sandstone. 
Ironstone nodules of a flattened type — evidently from the Coal Measures 
— occur in great numbers, while fragments of chert, often cuboidal in 
form, were by no means rare. The pebbles were somewhat irregularly 
laid, but there was a general tendency tor them to lie with their long 
axes north-west and south-east, parallel to the present course of the 
Kiver Aire. The gravel, when treated with dilute hydrochloric acid, 
showed a brisk effervescence, and this was found to be due to small 
fragments of limestone and calcite in the finer material intermixed 
with the gravel. Small pieces of grit and Coal Measure sandstone 
effervesced slightly, and seemed to be more or less impregnated with 
calcite. The heavy minerals and general mineral composition of the 
finer material was found to be identical with the sands associated with 
these deposits, and do not call for a separate description. 
Sands. 
The thickness of the beds was very variable, as the sections show, 
and the current bedding very pronounced, the general direction indi- 
cating deposition by water flowing south-east. 
A microscopical examination of the sands shows the size of the 
grains to be very variable, the pieces of grit and sandstone being the 
largest. These were distributed irregularly through the sands. The 
fragments and minerals present (neglecting the heavy minerals to be 
named later) included sandstone, ganister, grit, chert, coal (occasion- 
ally forming bands), limestone, ironstone, quartz, felspar and mica. 
This is just such an assemblage as would be yielded by the rocks 
