42 Mr. Webster's Reply to Dr. Fitton. [Jan. 



know of those of the UnderclifF, afford an additional evidence 

 in favour of the identity of these beds. 



We have another section of the strata below the chalk, de- 

 scribed in Mr. Conybeare's '-'Outlines," p. 162. He states that 

 in the parish of Roak, in Oxfordshire, a stone lies under the 

 chalk, and is worked for building-. The fossils found in it 

 (hamites, turrilites, inocerami, scaphites, and ammonites) agree 

 with those of the Undercliff; and it stands upon the Tetsvvorth 

 clay, which again rests upon an iron sand. 



The stone of Totternhoe, in Bedfordshire, and of Reach, 

 in Cambridgeshire, is soft, immediately below the chalk, and 

 is similar to that of Roak and Reigate. 



I have already mentioned my original opinion, that the struc- 

 ture of the weald and that of the Isle of Wight are the same, a 

 circumstance that it was impossible to comprehend upon the 

 supposition of Mr. Conybeare ; but my late discovery of the 

 Hastings limestone in that island, having enabled me to speak 

 with more confidence on the subject, as affording me a fixed 

 point in each of these places (see the abstract of my paper on the 

 subject, together with the table of the equivalent beds in the 

 two places in the Annals for Dec. p. 465), the identity of the 

 rock of the Undercliff with the Reigate stone is no longer 

 doubted, and is admitted by Dr. Fitton. The rock of the 

 Undercliff, Isle of Wight, is immediately below the chalk marl, 

 and hiis the general characters of the Reigate stone, although 

 its thickness is much more considerable, and its beds of chert 

 and hard limestone are in proportion more striking. It rests 

 upon a bed of blue marl, and that again upon a ferruginous sand. 



Thus we see that almost every where below the chalk in 

 England (or rather below the chalk marl according to my 

 arrangement), there is a stone composed of siliceous grains, 

 mica, and dark gTeen particles, with a calcareous cement. In 

 some places it is very hard ; in others soft, and fit to be em- 

 ployed as firestone ; and in others again too soft for this pur- 

 pose, and scarcely distinguishable from the common chalk marl, 

 into which it sometimes passes. This stone also varies much 

 in .colour, chiefly from the greater or less proportion of green 

 particles dispersed through it. Its fossils are also very unequally 

 distributed ; those which are the most characteristic of the bed 

 are inocerami, hamites, turrilites, trochi, aicyonites, ammonites, 

 &.C. It is to this bed, as appears to me, that the name of 

 green sand was originally given by English geologists ; and from 

 the above and similar observations, 1 conchide that the green 

 sand bed in the vale of Pewsey is the same with the rock of 

 the Undercliff, Isle of Wight, and with the Reigate stone. 



Let us now attend to the second question ; viz. whether the 

 Woburn sands belong to the Nutfield range, or to the Hastings 

 beds? 



