THE 



aEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE IV. VOL. IX. 



No. VL— JUNE, 1902. 



OE-io-iivrj^Xi ^A^I^TIOXJ:H]S, 



I.— Ckeechbakrow in Purbeck. 



By W. H. HuDLESTox, M.A., F.E.S., F.G.S. 



I. Introductory. 



rpHE Isle, of Purbeck possesses numerous points of geological 

 JL interest, and its coast scenery has been celebrated, in con- 

 junction with that of Lulworth, by many writers and artists. The 

 classical work of Sir Henry Englefield, assisted by Webster, in the 

 early part of the last century, served to make known some of the 

 most interesting features of the coast, such as are more or less 

 obvious to all who venture to sail beneath its cliffs. Of late years 

 the geology of the Isle of Purbeck has attracted the attention of 

 the officers of the Geological Survey, and has come in for a con- 

 siderable amount of description at the hands of H. B. Woodward, 

 Aubrey Strahan, and Clement Reid, in their respective departments. 

 The zones of the Chalk in this region have also been admirably 

 described by Dr. Rowe and his coadjutors, mostly from coast 

 sections. 



The interior of the Isle of Purbeck has likewise attracted a fair 

 amount of attention, and those who have participated in some of 

 the excursions of the Geologists' Association during the last quarter 

 of a century will not be altogether ignorant of its leading features. 



One of the chief of these features is the long ' Purbeck Hill,' 

 consisting of a narrow outcrop of Chalk, tilted at a high angle 

 towards the north, which stretches from Arish Mell Gap, just 

 underneath Lulworth Castle, on the west, to Swanage Bay on the 

 east. The celebrated 'overthrust' fault, the subject of many 

 a drawing and photograph, is seen in the middle of the Chalk 

 formation between Ballard Point and Old Harry on the northern 

 horn of Swanage Bay, which also forms the most easterly point 

 of the Isle of Purbeck. The effects of this fault, or axis of maximum 

 tension, may be traced for the most part along the northern slope 

 of the Purbeck Hill, though its effects are not so obvious as in the 

 Lulworth district further to the west. The principal fact to be 

 noticed in this connection is that the so-called Purbeck Hill may 

 be said to divide the Isle of Purbeck into a southern and a northern 



DECADE IT. VOL. IX. NO. VI. 16 



