Chiseldon to CoUingbourne. 95 



shore, and the shore-line of the upper greensand was to the north 

 and west, and at the close of the period, Avhen the Warminster heds 

 were heing deposited, the Avhole of south-eastern and central England 

 was covered by a sea, nowhere more than one hundred or one 

 hundred and fifty fathoms deep, and gradually shallowing westward. 

 To the south-west it stretched to the borders of Daiimoor, and 

 washed the foot of the Quantock Hills ; the valley of the Bristol 

 Channel was a deep iidet, and thence the shore-line swept north- 

 ward below the hills of Griamorgan, Monmouth, and Hereford. 

 The sea then trended north-east to Derbyshire, and passed uj) the 

 eastern side of the Pennine range. 



I am here following Jidies-Browne and liis book, the "Building 

 of the British Isles." 



This sand is greenish grey in colour,^ consolidating into a sand- 

 stone at times ; pale calcareous sandstones and chert also occur. 

 These calcareous sandstones are sometimes called firestone, and are. 

 well developed at Eeigate. The green colour is due to glauconite,, 

 a hydrous silicate of iron, alumina, and potash. 



The ujoper greensand was laid down near a coast-line, and 

 indicates a physical change and a diversion from the mud-bearing 

 currents of the gaidt sea. 



As the outcrop of the upper greensand is not very mde, the bed 

 not being very thick and the dip a good one, the space it occupies 

 on the siu'face of the ground is a naiTOW one. 



This is bed number 3 in the diagram, where it is seen rising up 

 under the chalk in the cutting and then spreading out on the map 

 by Badbmy, Liddington, and Wanborough. 



But naiTOw as the outcrop is, it has a marked effect on the 

 scenery, as may be seen in the narrow and picturesque gorges cut 

 through it at Chiseldon and Wroughton, to mention only two 

 instances out of many. All along the escarpment of the chalk, 

 villages are foimd to be situated on the outcrop of the upper green- 

 sand. 



Effcch of Escarpments on the Shape of Parishes. 

 The variety of soil, too, found to exist in passing fi'om the top of 



