418 CARTER : GLACIATION OF DON AISD DEARNE VALLEYS. 
Limestone (Fig. 4), and to have been re-excavated by a small 
stream flowing from Conisbrough Park and Edlington in pre- 
Glacial times. The boulder-clay is a stiff brownish or bluish 
tiU, about forty feet in thickness, crowded with large and 
small erratics, which thins away northwards to three feet in 
Wood's pit, lying on an uneven surface of Bunter sandstone. 
During the excavations for the Doncaster Workhouse the 
section was well exposed. " The clay was seen to rest upon 
the sandstone at angles varying from 40° to 10°, the steeper 
angles being at the western end, and the slope being from north 
to south. In some sections large angular fragments of the 
sandstone were seen imbedded in the clay (Plate LIX.)."* In 
this deposit a remarkable assemblage of travelled boulders has 
been found, including Shap granite, Threlkeld microgranite, Bor- 
rowdale andesite and andesitic agglomerate, Eycott Hill diabase, 
Eskdale granite, and a schist with garnets. f Carboniferous 
limestones and cherts are common, many being highly fossil - 
iferous, and Millstone Grit and material from the Lower and 
Middle Coal Measures are very common. Lumps of Permian 
marl and blocks of fibrous gypsum are plentiful, as are blocks 
of Magnesian Limestone, " a large percentage of which contain 
casts of Axinus, Mya, Turbo, &c. The fossil bed whence they 
are derived crops out near Hampole, and at several other places 
along the escarpment of the Magnesian Limestone, e.g., Conis- 
brough and Clifton."! Mr. Corbett reports finding this bed 
cropping out at Hooton Pagnell on the west side of Frickley 
gorge, where it is about 15 feet thick. || 
In the neighbouring Don gorge drifted gravels have been 
found near Sprotborough up to 150 feet on the Limestone. 
"At Cusworth boulders up to a ton in weight are turned up in the 
fields by ploughing. These consist of grits, ganisters. Mountain 
Limestone, Whin Sill, quartz porphyry, and basic rocks. "§ 
* H. H. Corbett, Glacial Geology' of the Xeighbovirhood of Doncaster, 
Naturalist, 1903, p. 47. 
t Supposed by the author to be Scotch. 
X H. H. Corbett, see ante, p. 49. 
ii H. H. Corbett, Report Yorks. Boulder Com., 1900. 
§ H. H. Corbett, Naturalist, 1903, p. 49. 
