328 The Geology of Devizes. 
Fig. 7.—Structure of Chalk Rock (magnified sixty times). 
The Chalk Rock is found near the top of Morgan’s Hill and 
Oldbury Hill, and has been dug from shallow pits in many places 
all round the borders of Salisbury Plain. 
7. Upper Chalk. Above the Chalk Rock comes the Upper Chalk, 
a pure soft white Chalk with numerous layers of flint nodules. This 
Upper Chalk is not well exposed anywhere near Devizes, so I do not 
propose to describe it in detail, though near Salisbury it is some 
600ft. thick, and in the Isle of Wight more than 1000ft. There is 
no doubt that it originally spread across the whole Vale of Pewsey, 
and, together with the underlying Chalks and Greensands, spread. 
westward across Somerset and Gloucester to the mountains of Wales. 
The whole of England was submerged beneath the ocean in which 
the Upper Chalk was deposited, and it is not even certain whether 
the summits of the highest mountains in Wales remained above the 
surface of the water. Some of my readers may ask, ‘“ Where has 
all the great tract of chalk gone to?” The answer is that it has 
been washed off all those parts where it is not now found; but 
certain stones remain to testify to its former existence, for there are 
few parts of England where chalk-flints may not be found in greater 
or less abundance, and all these flints have been derived from the 
