212 
A GLACIAL DEPOSIT NEAR DONCASTEE. BY THOMAS HILL 
EASTEEFIELD (PL. Vila) 
Speaking some months ago with Mr. Furnival, of Doncaster, our 
conversation turned upon glacial deposits, and Mr. Furnival stated 
that the clay in a clay pit two miles south-west of Doncaster, and 
known as Balby Brick Works, appeared to be of the nature of a 
"Boulder-Clay." I took an early opportunity to visit the pit, and 
found it to be undoubtedly what is known as " till." It consists of 
a tough dark-blue clay, packed with boulders up to half-a-ton in 
weight. The boulders are mainly of local origin, magnesian- 
limestone, clay-ironstone, and coal-measm^e shales and sandstones 
being most abundant ; though not unfrequently, carboniferous lime- 
stone and upper permian marl with gypsum are found, as are also a 
few small boulders of hsematite. One very small block appears to 
be of the nature of a quartz-felsite. Very many of the boulders are 
beautifully scratched and polished by the action of the ice. 
From a boring made some years ago it appears that this clay is 
sixty feet in thickness. It covers the outcrop of the New Red 
Sandstone at its junction with the Magnesian Limestone, there 
being a limestone quarry near one end of the clay, and a sand-pit 
close to the other, as in the section on the opposite page. 
The section is ideal, only being intended to convey a l ough 
notion as to the general lie and position of the beds. 
The clay consists of two parts, an upper and a lower, and the 
surface of the lower appears to have been smoothed by the ice before 
the upper w^as deposited. This division in the clay seems to indicate 
a cessation in the glacial action, but there is no distinctive difference 
between the boulders of the upper and those of the lower clay, 
though there is rather more magnesian limestone in the lower than 
in the upper. 
