Ixxiv. PRESIDENT'S ADDRESS. 



This theory is supported by the presence of an abundance of 

 fossil trees where the brecciation is most intense. He agrees 

 with Mr. Clement Reid that the outliers at Bincombe and 

 Portisham belong to the Bagshots and not to the Reading beds 

 as marked in the map of the Geological Survey, nor to plateau 

 gravels as supposed by Sir Joseph Prestwich. Mr. Strahan 

 groups two sets of disturbances one post Cretaceous, the other 

 inter Cretaceous. The first includes the Isle of Purbeck fault, the 

 second the anticline, which extends from Ballard Point to the 

 coast, near West Lulworth, where it passes out to sea. There are 

 three others the Ringstead fold, the Ridgway fault, and Anti- 

 cline, which includes the Chaldon anticline and the Litton Cheney 

 fault, extending about a mile on either side of that village. 

 In the Isle of Purbeck, the disturbance has not only bent the 

 rocks, but faulted them in a remarkable manner. From the 

 fault, southwards to Ballard Point the strata are vertical, or nearly 

 so. The horizontal strata as they approach the vertical, turn 

 upwards in a great curve. The bedding of the strata shows 

 signs of pressure ; the flints are not only broken to fragments, 

 but the fragments are more or less separated from each other, 

 and the entire mass of chalk hardened to the consistency of 

 limestone. The chalk above the curve is but little changed. 

 The whole of the chalk has been more or less broken and 

 re-consolidated, so that much of it may be described as fault- 

 breccia, which ruptured the chalk. 



The effects of the Intra-Cretaceous disturbances are not 

 observable in Purbeck, but they may be inferred by the erosion 

 at the base of the Gault, near Lulworth ; they are better displayed 

 at White Nose and in the cliff near Osmington Mills. The 

 Bibliographical Appendix of twenty-five pages on the Geology, 

 Mineralogy, and Palaeontology of Dorset, indicates the interest 

 eminent men have taken in this corner of England, whose 

 names shine in the pages of the highest national scientific 

 works. 



