1869.] WILTSHIRE HTJNSTANTON RED CHALK. 191 



" The specimen of Gault," Mr. Forbes writes, " is, properly speak- 

 ing, a marl (not a clay), being a mixture of ferruginous clay with a 

 considerable quantity of carbonate of lime. The iron contained in 

 it is all in the state of protoxide, amounting to 5*96 per cent., which 

 would be equivalent to 6*606 per cent, of sesquioxide (red oxide) 

 of iron, or to 4-62 per cent, metallic iron. The Hunstanton Red 

 Chalk contains more carbonate of lime and much less clay than 

 the above ; and all the iron it contains is in the state of sesquioxide 

 (red oxide), which amounts to 5*96 per cent., or is equivalent to 

 5*28 per cent, of protoxide of iron, or 4-10 metallic iron in the sub- 

 stance ; it consequently, notwithstanding its red, or what generally 

 would be termed ferruginous appearance, in reality does not contain 

 quite as much iron as the Gault does, which has no such aspect ; 

 there seems to be no objection, from a chemico-geological point of 

 view, why these rocks may not be representatives of one another. If 

 the Gault were subjected to any oxidizing influences it would as- 

 sume the red colour of the Hunstanton rocks, as it does also by 

 burning." 



Summing up, therefore, the evidence brought forward, observing 

 that the fossils of the Eed Chalk agree for the most part with those 

 from the upper portion of the Gault of Folkestone, that the red band 

 of Hunstanton agrees in position with the Norfolk Gault as being 

 below the Chalk and above the Carstone, that the presence of iron 

 brings it into concord with the Gault of Kent, it would appear that 

 the Eed Chalk is the representative of the upper portion of the 

 typical English Gault (as seen in the Folkestone Section), and not of 

 the Upper Greensand. 



If the Upper Greensand exist in the Hunstanton series, its place 

 must be in the band h, which rests on the Eed Chalk, and which is 

 so abundantly stored with S^ongia paradoxica and Avicula gry- 

 johcBoides. 



Discussion-. 



The Presideis't remarked that the vertebrae from the Eed Chalk, 

 noticed and exhibited by Mr. Wiltshire, were undoubtedly those of 

 Plesiosaunis latispinus of the Upper Greensand ; but associated with 

 these were other bones which he could not identify with any part of 

 the skeleton of Plesiosaurus. 



Mr. Etheridge spoke in confirmation of the author's views, re- 

 ferring especially to the Palaeontological evidence. 



Mr. S. Hughes mentioned a boring near Hitchin where a hard 

 sandstone, resembling Carstone, was found immediately below the 

 Gault, the latter having a thickness of 280 feet. 



Mr. David Forbes remarked on the similarity in the amount of 

 iron present in rocks so dissimilar as the Eed Chalk and the blue 

 clay of the Gault. 



Prof. Morris noticed the similarity of the Carstone of Hunstanton, 

 and its equivalent beds, to the Hilsthon and Hilsconglomerat, espe- 

 cially in their containing abundance of pisolitic iron-ore. He then 

 adverted to the marked difference of the Lower Greensand of the 



