Clmcldon to Collinghourne. 103 



upper greensand which outside Savemake Station can be seen 

 dipping north, is seen in the cutting just before Grafton is reached 

 to be dipping steadily and gently ^outh, so that the same series of 

 strata is repeated from Grrafton to Collingbourne, where the upper 

 chalk again makes its appearance, as was seen between Chiseldon 

 and Marlborough. 



It is interesting to compare the effect on the width of the outcrop 

 of the strata of the sharp northern dip to the north of Savernake, 

 with that of the gentle south dip from Grrafton to Collingbourne. 



It will be seen that the upper, middle, and lower chalk (4a, 

 4b, and 4c in the diagram) occupy a very small space north of 

 Savernake as compared with the wider space occupied by the same 

 beds between Grrafton and Collingbourne. The sharp dip, too, 

 affects the line of the outcrop which west of Burbage is seen to be 

 almost straight, while to the east of that place it winds about and 

 follows very much the natural contour of the country. 



I have now taken you all the way from Chiseldon to Colling- 

 bourne on our geological railway journey, and necessarily at express 

 speed, as I have only sketched the bare outline of the great geological 

 story that this joiimey unfolds. But I trust I have not wearied 

 you, and that thus running along you have been able to read 

 something of the main geological features of the country through 

 which this most interesting line passes. 



In conclusion a few words may perhaps be said as to the distri- 

 bution of the chalk in England. From its western outcrop in 

 Antrim, in Ireland, the cretaceous sea, shallow in the west of 

 England, deepened to the east and south, so that in the Isle of 

 Wight the chalk reaches 1700ft., its maximum thickness in England. 

 No well in Marlborough has gone through the upper cretaceous 

 beds, and we do not know what lies beneath that formation in the 

 Vale of Pewsey. A boring there would be a most interesting 

 experiment geologically, and might yield most important results 

 from an industrial point of view, as the upheaval there may have 

 brought up the older rocks, with perhaps the coal-bearing strata, to 

 within no very great distance from the surface, near enough, possibly, 

 in the event of coal being present, to aUow of its being worked. 



