THE HAMPSHIRE ANTIQUARY <- NATURALIST. 



59 



(two brickearths and three gravels), which is quite 

 new, Drift-mapping not having been invented 

 when the old map was made. 3. The great exten- 

 sion of the Hamstead Beds (the uppermost division 

 of the great Fluviomarine Series), which, originally 

 shown as two patches west of the Medina, have now 

 been proved to spread across the island, from just 

 east of Yarmouth to Brading, and to reach southward 

 sometimes to within half-a-mile of the outcrop of the 

 Chalk. 4. The separation of the Bembridge Lime- 

 stone from the overlying clays, instead of the massing 

 together of the two. 5. The division of the Chalk ; 

 though it was found impracticable to separate the 

 Lower and the Middle Chalk, as has been done in 

 some other places. 6. The division of the Upper 

 Greensand by marking the chert- beds, where 

 practicable. 7. The separation of the Lower Green- 

 sand into four groups. 8. The mapping of a layer of 

 sandstone in the Wealden Beds. 



The new map therefore is not only more precise, 

 but also much more elaborate than the old one. 



Though the work is published only on the one- 

 inch scale, it should be understood that anyone can 

 have a copy of any six-inch sheet, by paying the cost 

 of making such, and it is to be hoped that Corporations 

 and other Sanitary Authorities will avail themselves 

 of this. For general purposes, of course, the one- 

 inch scale is handy, but for special work it is too 

 small. 



It should be mentioned that the sheet of so-called 

 " Horizontal Sections " across the Isle of Wight has 

 also been revised, in accordance with the new work. 



Turning to the Memoir, which will perhaps have 

 the greatest interest for the general public, we may 

 note that it is just twice the size of the earlier edition. 

 The Cretaceous part is by Mr. Strahan, the Tertiary 

 pait by Mr. Reid, each author sharing in the 

 description of the Drift and of other matters common 

 to the two tracts. 



It opens with a note of sadness, for Mr. Bristow, 

 whose last official work was the correction of his intro- 

 ductory notice, died whilst the work was passing 

 through the press. 



Of the Wealden Beds, the oldest that occur in the 

 island, we are told that they consist of variously 

 coloured clays below and chiefly dark shales above, 

 with freshwater shells. The most interesting part 

 of this series perhaps is the " Pine Raft," with its 

 mass of prostrate tree-trunks, to be seen only at low 

 water at Brook Point. 



The Lower Greensand, which succeeds, is a marine 

 formation, and here conformable to the Wealden 

 Beds, though the division between the two is sharp. 

 Whilst about 400 feet thick at Compton Bay, a few 

 miles eastward it is 800 or more. Some beds are 

 fossilifcrous, and sometimes abundantly so. The 

 uppermost division, the Carstone (a ferruginous grit) 

 passes up into the Gault, a clay 120 feet and upwards 

 in thickness. 



This last, locally known as " blue slipper," is the 

 bed that has brought about the great landslip, after 

 the manner of clays. It will be satisfactory to resi- 

 dents of the Undercilff to be told that their beautiful 

 tract is likely to last, and " that the strata now form- 

 ing the cliff will never be in a position to slide so 

 readily as those portions that have already gone," 

 though we are at once cautioned that " still, as the 

 sea, in the course of centuries, removes the fallen 

 debris which forms the coast, the movements will 

 doubtless be renewed from time to time." 



The Gault passes up into the Upper Greensand, a 

 formation which, though only from 80 to 120 feet 

 thick, is the cause of some of the chief beauties of the 

 island, such as the mural cliffs that tower above the 

 picturesque broken masses of the Undercliff, them- 

 selves fragments of the same formation, and the bold 

 inland brow of Gatcliff (visited by the Hants. Field 

 Club last summer). These marked rocky features are 

 " due to the hardness of a bed composed of alterna- 

 tions of chert and sand," and the chert abounds with 

 sponge-spicules . 



The Chalk, into which the Upper Greensand 

 passes up, reaches right across the island from east 

 to west, forming the highest ground, the long undu- 

 lating hill-range that is so conspicuous from the main- 

 land. For the most part this range is narrow, and 

 the beds vertical or highly inclined ; but south-west 

 of Newport they flatten southward, and spread out 

 to a wider tract, of the former extent of which the out- 

 liers, or detached masses around Ventnor bear 

 witness. It is here that the Chalk reaches its 

 greatest thickness in England, for, whereas under 

 London it is less than 650 feet thick, the Upper Chalk 

 alone, with its marked layers of flints, is more than 

 double that, being estimated at over 1,350 in the Isle 

 of Wight. The Middle Chalk is 180 feet, and the 

 Lower Chalk over 200, but these figures are not ex- 

 cessive, though they bring the total to about 1750. 



It seems a pity that the name Chlontic Marl is still 

 kept for the basal bed of the Chalk, as it does not con- 

 tain the mineral chlorite, the green grains being 

 glauconite ; but geologists are horribly conservative 

 and dreadfully illogical. 



To the Chalk succeed, with a sharply marked 

 plane of separation, the Tertiary beds, the uptilted 

 junction being well shown in Alum Bay and, less 

 clearly, in Whitecliff Bay. We have first the 

 mottled clays, with occasional sand, of the Reading 

 Beds, and then the London Clay, with its fossiliferous 

 and pebbly basement-bed, the formation being seen 

 in section at no other places than the above-mentioned 

 Bays. 



Above this come the Lower Bagshot Beds, to 

 which a thickness of over 660 feet is assigned, in 

 Alum Bay, though it is doubtful whether part of the 

 overlying Bracklesham Beds is not included. As the 

 series here is composed of alternations of clays and 

 sands, whilst at Whitecliff Bay we find onl}- sand, 



