( 4ii ) 
of its peculiar Unduoufnefs, or the running of the 
adjacent Sand imperceptibly among it, breaks itlelf 
into Pieces of all Angles and Sizes. 
For the Geographical Situation of thefe Pits, they 
are digg’d in that Ridge of Sand-Hills by Woburn j 
which near Oxford is call’d Shotover • on which lies 
Hewmarket'Heath by Cambridge^ and which extends 
itfelf from Eaft to Weft, every where, at about the 
Diftance of eight or ten Miles from the Chiltern Hills, 
which in Cambridgefiire are called Gog-Alagog ^ in 
Bucksy and Oxon, the Chiltern Hills, from the chalky 
Matter, of which they chiefly confift: which two 
Ridges you always pafs, in going from London into 
the North, North-Eaft, or North-Weft Counties in the 
Manner I before-mention’d : After which you come into 
that vaft Vale, which makes the greater Part of the 
Midland Counties of Cambridge^ Bedford, Bucks, 'North- 
ampton, Oxford, and Gloucefter, and in which are th» 
Rivers Cam, Oufe, Nen, Avon, Ifis, and others , which 
I take Notice of, becaufe it confirms what you fay of 
the regular Difpofition of the Earth into like Strata, 
or Layers of Matter, commonly through vaft Trails, 
and from whence I make a Queftion, whether Fullers- 
Earth may not probably be found in other Parts 
of the fame Ridge of Sand-Hills, among other like 
Matter. 
VII. Invi- 
