DEPOSITS OF THE LEEN VALLEY. 
Ill 
the alluvial plain. The Leen itself flows about fifty yards west of 
where the excavations were made, that is, from the end of the section 
shown in Fig. 2. In this part of the Leen valley the relations of the 
various deposits of gravel, sand, and clay that underlie the alluvial 
plain could he seen to better advantage than at Radford. Another 
link in the chain of physical events which have happened in this 
valley since the Glacial period was disclosed, too, by this excavation. 
The deposits exposed by the cutting at Basford seemed to belong to 
three distinct stages in the history of the Leen valley. Placed in the 
order of their relative age we had— 
3. Recent alluvial sand, silt, and peat. 
2. Torrential gravel. 
1. Glacial drift. 
At Radford the ground was opened on the west side of the river. At 
Basford, however, the wells were sunk on the east side of the valley. 
As at Radford, the most recent deposits of the Leen were found to 
occupy a hollow scooped out of the solid rock. Here, too, only one 
side of this alluvial hollow was seen in the section, and it descended 
gently towards the present course of the stream. The oldest deposit 
met with at Basford was the Boulder Drift. This was composed of a 
mixture of red, brown, white, and greenish-yellow sand—a mottled, 
tenacious mass, studded with pebbles of all sizes up to small, well- 
rounded boulders. No regular bedding or stratification could be dis¬ 
cerned in the mass. The pebbles were imbedded at all angles, instead 
of lying more or less horizontally, as they would have done if the 
deposit had been calmly accumulated under water. Here and there, 
however, puckered strings of pebbles showed that the mass had been 
kneaded and crumpled by some powerful force acting laterally, 
and that the deposit had been then still further compacted by 
enormous pressure from above in such a way that the pebbles 
were now tightly wedged into the matrix. The deposit had 
clearly been formed by some powerful physical agent scouring 
the surface of the country and pushing the materials in 
front of it as it went along until they lodged in sheltered hollows, 
as in this case. That agent was undoubtedly ice. This deposit, 
then, takes us back to the Great Ice Age, when Britain, in common 
with the whole of Northern Europe, was enduring climatal con¬ 
ditions very much like what now prevail in Greenland and the 
Arctic regions. The pebbles in this Drift consisted chiefly of 
quartzites, along with pebbles of millstone grit, coal measure sand¬ 
stone, and occasionally lumps of the underlying sand rock, caught 
up and incorporated in the mass by the ice-plough. A good deal of 
the matrix of this Drift was evidently derived from the wearing down 
of the Lower Mottled Sandstone, which forms much of the ground to 
the north and west. But the coarse, bluish-white sand or pounded 
grit, that it contained must have had a different source. The Drift was 
from two to six feet thick, and rested on a slightly uneven surface of 
the Lower Mottled Sandstone, towards the bottom of the eastern slope 
