﻿A. J. Jukes Browne — On the Upper Greensand, etc. 353 



Feet 



Upper ( Parallel layers of soft rock and of hard clierty sandstone 37 



Greensand \ Sand with layers of stone and chert ... 67 



104 



Light-coloured Gault becoming bluer 43 



Beds of decided blue colour .. ... 103 



Gault 



Lower Greensand in various beds 



146 



250 

 These measurements and divisions, although apparently taken 

 with great care, do not seem at first sight to correspond with those 

 given in the Survey Memoir on the Isle of Wight; but it is re- 

 markable tljat the combined thickness of the Gault and Upper 

 Greensand should be estimated in both at exactly the same amount, 

 viz. 250 feet. Of this, 150 feet are assigned to the Greensand by the 

 Geological Survey, including 50 feet of clayey micaceous sands at the 

 base. Now I think it is not improbable that these are the " light- 

 coloured Gault " mentioned in the above section, which, if added to 

 the other beds, makes the thickness very nearly the same, viz. 147 

 feet. This is of course a conjecture ; but as they are certainly 

 passage-beds, it would not be surprising to find them placed in the 

 lower formation by some authors, and in the higher by others. 



Captain L. L. B. Ibbetson seems also to have excluded these beds, 

 when he states that the Upper Greensand is about 100 feet thick ; ^ 

 he does not mention the locality where this was measured, but he 

 gives a detailed list of the strata observed in descending order ; as 

 this has never been reproduced elsewhere, I give the following 

 abridgment of it : — 



ft. in. 



f 1. Zones of Chert and Eag, with Pecten orbicularis, P. 5-costatus, 



I Serinda concava and Sipkonia 

 «( 2. Conglomerate of Chert and Rag (much rolled) 



I 3. Bands of Chert and Firestone... 



l^ 4. Freestones separated by layers of Eag 



f 5. Eag and Malm alternating 



I 6. Mammillary Eag, round Chert, sandy boulders, with phos- 

 J phate of lime (? nodules) ... 



] 7. Malm and Eag 



I 8. Fossiliferous Malm ... .. 



l^ 9. Malm and Eag, with numerous (Serju^^^^ 



103 6 

 The close agreement of this section with that of Mr. Simms is 

 made more apparent if it is still further abbreviated thus : — 



ft. in. 



Zones of Chert, Firestone and Freestone 35 8 



Alternations of Eag and Malm... ... ... ... ... 67 10 



103 6 

 and it is possible therefore that the thicknesses were estimated at the 

 same place, viz. at St. Catherine's Down. 



About the same time (1848) Messrs. Paine and Way published an 

 important paper on the Phosphatic Strata of the Chalk Formation,^ 



^ Notes on the Geology and Chemical Composition of the Various Strata in the 

 Isle of Wight, London, 1849. 



^ Journ. Eoy. Agric. Soc. ser. i. toI. ix. p. 56. 



DECADE II. — vol. IY. — NO. VIII. 23 



15 







4 







6 



2 



11 



6 



16 



8 



1 



6 



6 



8 



3 







40 







