306 



[Proc. B.N.F.C. 



so fully represented in Dorsetshire belong principally to the 

 Mesozoic or secondary division of the sedimentary class. Sands 

 and clays of Tertiary age also occur ; but, so far as the coast is 

 concerned, they are much less in evidence than the strata of 

 Mesozoic age. The dominating systems represented on the coast 

 line are the Jurassic and Cretaceous, and as the rocks are, 

 generally speaking, fairly fossiliferous, the cliff sections constitute 

 a classic hunting ground for geological students. In considering 

 the Geology of the Weymouth district and the evolution of its 

 present physical features it is essential to bear in mind that the 

 Jurassic and Cretaceous systems of this country were continental 

 in their character rather than insular. On the opposite coast of 

 France we have the counterparts of almost all the secondary rocks 

 that occur now on the Dorset coast. The continuity has been 

 broken up in Tertiary times. The present channel is merely a 

 plain of marine erosion, the denudation of the connecting beds of 

 Cretaceous and upper Jurassic deposits being no doubt facilitated 

 by the folding, faulting, and crushing of the rocks, brought about 

 by subterranean forces. The long ages that elapsed during the 

 deposition of the secondary system of formations witnessed of 

 course several oscillations of level over the area in question. The 

 strata clearly point to an alternation of periods of marine, 

 estuarine, freshwater, and terrestrial conditions. The evidences of 

 disturbances are no less clearly revealed, and much of the 

 surpassing interest of the Dorset cliffs, from both the geological 

 and scenic points of view, is directly due to such crustal dis- 

 turbances and the carving operations of natural agencies in 

 subsequent times. In the Isle of Portland, south of Weymouth, 

 and in the Isle of Wight we have relics in the channel which have 

 been preserved from the universal planation of the secondary 

 rocks between England and France. The greatest depth of water 

 between Weymouth and the nearest French territory does not 

 exceed 45 fathoms, and between Dover and Calais about 30 

 fathoms. In County Antrim we are fortunate in having some 



