156 THE GEOLOGY OF THE PURBECK HILLS. 



importance to justify the expense of borings being made, 

 by which alone the third question can be answered, is a 

 matter for geologists to consider. 



THE ORIGIN OF THE CORFE MONTICLE AND THE DENUDATION 

 OF THE PURBECK ANTICLINE. 



These two problems are so intimately connected that it 

 will be convenient to treat them together. How the little 

 conical hill on which Corfe Castle stands came to be carved 

 out of the Purbeck chalk ridge, and the Corfe Double Gap 

 produced by the two streams, the Byle and the Steeple, 

 has always been a puzzle to geologists. Various explanations 

 have been given, but at present two theories hold the field. 

 The first is that advocated by Dr. Strahan, who considers 

 that Corfe Hill was carved out by ancestors of the present 

 two streams, which, draining the Purbeck anticline, cut 

 across the chalk ridge in close proximity, and so left the hill at 

 the centre of the gap. The late Mr. Hudleston, however, in a 

 short article he contributed to the " Wareham Pictorial Guide " 

 on " Corfe Castle Hill," considered that these two streams, 

 which are really affluents of the Corfe stream, which they unite 

 to form on the north side of the gap, were formerly united 

 in a single channel on the south side of the hill. This is in 

 keeping with the manner in which the rivers of the Weald 

 of Sussex have similarly cut down their channels across the 

 intervening chalk ridges. For two separate streams to cut 

 separate channels for themselves through chalk within a few 

 hundred yards of each other is an improbable phenomenon, 

 and it is doubtful if any example of such can be produced. 

 We therefore accept Mr. Hudleston's view, in preference to 

 Dr. Strahan's, that the Corfe gap was originally carved out by 

 a single stream, which afterwards became divided and cut 

 down the double gap, the eastern opening by the Byle, and 

 the western by the Steeple (also called the Wicken) brook, 

 which subsequently became united into the little Corfe stream 



