THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE II. VOL. IX. 



No. III.— MARCH, 1882. 



OE,ZC3-II5rJLIL -A-IiTIGLES. 



I. — On the Headon Beds of the Western Extremity of the 



Isle of Wight. 



By A. H. S. Lucas, M.A. Oxon, B.Sc, F.G.S. 



THE recent answer' to the recent questioning^ of the hitherto 

 accepted correlations of the beds of the Lower Eluvio-Marine 

 Tertiaries in the Isle of Wight and South Hants does not seem to be 

 universally accepted as decisive. It is obviously impossible for 

 foreign geologists to institute useful comparisons between British 

 and foreign subdivisions so long as we in England are quite at 

 variance on the stratigraphical and palseontological /a cis of the beds 

 in question. Yet these conflicting readings are what we have to 

 offer them at present. 



There has been no lack of able workers on the ground. The suc- 

 cession proposed by Forbes, and elaborated by Bristow, agreed and 

 in no way conflicted with the previoug stratigraphical results of such 

 observers as Prestwich and Wright. Lastly, we have the elaborate 

 defence of the Survey views in the memoir of Messrs. Keeping and 

 Tawney, comprising a mass of evidence as to both the order of the 

 strata and the distribution of life-forms, evidence peculiarly valuable 

 because of a kind not easily obtained, viz. that derived from years of 

 continuous observation of these ever-changing cliff-fronts. 



The general relations of the whole group can only be satisfactorily 

 determined after the primary question of the continuity or discon- 

 tinuity of the Colwell Bay and Headon Hill beds is settled. So far 

 there were two very definite views — with a perfectly distinct issue, that 

 the brackish-marine beds of Colwell Bay correspond to the brackish- 

 marine beds of Headon Hill which have been seen, or that they cor- 

 respond to some higher marine beds which have not been seen ; and 

 the arguments for each view were fairly before geologists. But, in 

 a paper recently published,^ Prof. Blake has advanced an entirely 

 new correlation, and adduces stratigraphical evidence in its favour. 

 The observations there recorded do not agree in some critical cases 

 with those of Messrs. Keeping and Tawney, though still less so with 

 those of Prof. Judd. There seems therefore a danger that the facts 

 and lines of argument may again be confused. The following 

 remarks are offered in the hope of contributing to recall attention to 



1 Q. J. G. S. vol. xxxvii. p. 85. ^ Q. J. G. S. vol. xxivi. p. 137. 



^ Proceedings Geol. Assoc, vol. vii. p. 151. 



DECADE II. — VOL. IX. — NO. III. 7 



