494. REPORT— 1873. 



Strata. Thickness. Deptli from surface. 



ft. in. ft. in. 



Pure white gypsum 3 142 6 



Gypsum, more or less pure, hard, and dark 14 6 157 



Blue shale 3 6 160 6 



Gypsum, in nodules and veins 12 172 6 



Gypseous marl 6 179 



Sandy marl G 179 G 



Black sulphurous shale 6 180 



Greenish sand, with nodules of black chert 21 201 



Sandy shale 30 231 



„ with more or less variations of eal- 1 



careous matter, and with interspersed chert- [■ 8 239 



nodules J 



Carbonate of lime, in veins intersecting ditto ... 2 241 



Indurated black sandy shale, very sulphurous ... 12 253 



Blacker ditto; softer 7 260 



Harder shales, with much chert 12 272 



Black horizontal shale, very Bulphurous 2 274 



„ 12 286 



Shale, paler in colour, with veins of gypsum 4 290 



Shale, darker and more sandy 2 292 



Shale 2 294 



The higher beds marked as " limestones " in the horing-scction are 

 mostly impure. These are the " bastard blues." Below these, in Eounden 

 Wood, there are other limestones known as the " Eounden greys,"' and then 

 come the "Dunk shaws." The " greys" and " blues " are easily identified 

 by the workmen whenever they occur. The " Dunk shaws " are peculiar in 

 character ; but as neither they nor the " Roiinden greys " have been identi- 

 fied in the boring, they may be a local peculiarity. The new discovery of 

 gypsum is an important addition to the Purbeck series of Sussex. The two 

 principal beds of gypsum consist of perfectly white alabaster. The gypseous 

 shales are dark in colour, but they contain .so much gypsum that, when 

 pulverized, they appear almost white. The gypsum is mostly evenly bedded ; 

 but that found in the shales is nodular and irregular in structure. It is not 

 improbable that at or near this horizon gypsum will occur over a considerable 

 area in the Sussex Purbecks ; and it probably occurs not far below the sur- 

 face at the bottom of the " rough field " in Eounden Wood. 



With regard to the dci^th at which the Palaeozoic rocks are likely to occur 

 beneath the Weald, I may remind you that 700 feet has been mentioned as 

 a probable minimum, and 1700 feet as a probable maximum. It would 

 seem, from borings already made in other districts, that the depth of the 

 palaeozoic floor below the present sea-level is to a large extent independent 

 both of the newer formations above it and of the apparent disturbances which 

 are supposed to have affected them. The borings at Kentish Town, Harwich, 

 Ostend, and Calais, all reach the palaeozoic floor at a depth only slightly 

 exceeding, or slightly less than, 1000 feet below the sea-level ; and in these 

 cases the higher strata passed through are of very varying character and 

 thickness. These, however, are all on, or to the north of, the supposed westerly 

 extension of the "Axis of Artois," and it is possible that ditferent conditions 

 prevail to the south of that line. 



I may also remind you that, in the Pays dc Bray, Carboniferous Limestone 

 occurs at a depth of 59 feet from the surface, underlying Kimmeridge Clay. 

 It is this presence of the Carboniferous Limestone in this position which gives 

 some slight hope of the occurrence of Coal-measures near Boulogne and in 

 our Wealden area further west. Mr. Godwin- Austen has pointed out that 



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