88 



H. KEEPING AND E. B. TAWNEY ON THE BEDS AT 



the estimate in the paper above referred to, we shall certainly have 

 to abandon this section in favour of that of the Survey ; for the 

 thickness left, viz. 145 feet, more nearly corresponds with the 

 thickness of the Bembridge, Upper Headon, and Osborne beds, which 

 are stated by the Survey to exist at this spot, and whose thickness 

 would be 144 feet *. 



It would appear, therefore, that there is no necessity for supposing 

 " that, in a distance of little more than one mile, a mass of 

 beds 120 feet thick has expanded to 250 feet, and, further, that the 

 beds have been entirely changed in their mineral character." 



"We do not understand the warning (op. cit. p. 146) against 

 "trusting to the general impression which is produced by viewing these 

 beds from a distance," nor the purport of the following statement : — 

 " The strata of How Ledge and Warden Point are seen in such a true- 

 scale section to be clearly continued in precisely similar beds ap- 

 pearing underneath the gravel of Headon Hill." The section offered 

 to us is on rather too small a scale to show detail ; but, in our opinion, 

 the beds are inaccurately laid down in "Warden Cliff, and no such 

 bed as the Brockenhurst bed occurs at all in Headon Hill. 



Before we commenced drawing our section, we traced the beds 

 along the cliffs, measured their thickness, and obtained their height 

 above the sea-level at various points, but found it possible only to 

 show general results in the horizontal section ; the details are embodied 

 in the vertical sections. 



Vertical Section at North-east Comer of Headon Hill (fig. 1, 

 p. 91). — We may now proceed to a more detailed account of the 

 beds. We will begin near the N.E. corner, where the Bembridge 

 Limestone is seen, indicated on the section (op. cit. pi. vii. fig. 2) 

 with an asterisk, and lettered 250 feet altitude. (The quarry there 

 is not now at work ; but it is the place at which one of us has ob- 

 tained most of the finest specimens of Palceotherium which have been 

 found in the Isle of Wight.) We take the thickness from the 

 Survey Memoir as 25 feet. 



Beneath this, in the section (fig. 3, pi. vii.), we notice a blank 

 space with the legend " slopes covered by gravel and landslips." 

 We think this scarcely a correct description. Landslips exist in that 

 the clays and marls tumble and form taluses ; but we saw no gravel 

 covering the slopes between the Bembridge Limestone and Widdick 

 Chine ; nor indeed does it entirely conceal the beds between the 

 Bembridge and Upper Headon Limestones all the way toHeatherwood 

 Point in the other direction ; at intervals tumbled gravel conceals 

 a limited portion of them. 



The gravel west of Widdick Chine is not accurately depicted : the 

 thickness is exaggerated, while its horizontal extent is overestimated 

 here f , It does not appear in the cliff certainly beyond 80 yards 



* Taking the Bembridge Limestone at 25 feet, the Upper Headon and 

 Osborne at 119 feet, as read off their vertical section by scale, after altering 

 their lower boundary a few feet to correspond with our own. 



t Mr. Bristow (Forbes's Mem. p. 105) gives the entire horizontal extension 

 of the Lacustrine beds (Post -Tertiary) on both sides of the chine as 350 yards ; 

 the section under review makes the gravel extend about 720 yards. 



