INTRODUCTION. 5 



The names in italics indicate formations and groups not 

 exposed at the surface in the London district. 



For details and further information generally on the subject, 

 the reader is referred to the memoir on ' The Geology of London 

 and of part of the Thames Valley/ by W. Whitaker (Mem. Geol. 

 Surv.), 2 vols., 1889. 



Reference may also be made to his ' Guide to the Geology 

 of London and the neighbourhood,' Ed. 6, 1901, and to the 

 Proceedings of the Geologists' Association, the Essex Naturalist, 

 and other publications of local societies, in which are many 

 papers and Reports of Excursions relating to the London 

 District. The more important papers will be referred to in 

 the subsequent pages. 



CHAPTER II. 



UNDERGROUND GEOLOGY. 



PALEOZOIC ROCKS. 



At present the existence of the Palaeozoic floor has been 

 definitely proved at ten localities in our district. In two borings 

 only has the age of the rocks composing the floor been ascer- 

 tained by fossil evidence. At Meux's Brewery, Tottenham 

 Court Road, fossils of marine Devonian facies, Edmondia, 

 Chonetes, Orthis, Ehynchonella, and Spirifer verneuili, Murch., 

 were recognised in 1878. 1 



From a boring at Otto Monsted's Works, Southall, made in 

 1911-12, fragments of fossil fishes of Old Red Sandstone type, 

 Holoptychius and Boihriolepis, were obtained by Mr. E. Proctor, 2 



From the other borings (see Table, p. 9) which have reached 

 Palaeozoic rocks, red, grey, purple, and mottled sandstones and 

 marls have been recorded. The question of their age was the 

 subject of much discussion, Devonian, Carboniferous, and 

 Triassic ('New Red ') all being suggested. It was thought that 

 the existence of marine Devonian rocks at Meux's Brewery 

 rendered it unlikely that rocks of Old Red Sandstone type 

 would also occur. Now that this association is definitely known, 

 it is generally agreed that the rocks should be assigned to 

 the Devonian System in every case. 



The association of the two types may be paralleled in the 

 South of Ireland, Pembrokeshire, and North Devon, 3 districts 

 with which the Palaeozoic rocks of the London area appear to 

 be connected structurally by the great Armorican axis. 



1 Quart. Journ. Geol. Soc., vol. xxxiv, 1878, pp. 901, 903, 904. 



2 Quart. Journ. Geol. Soc., vol. Ixix, 1913, pp. 78-83 and Plate x. 



3 Evans, Dr. J. W., in discussion of Mr. Proctor's paper (op. cit.). 



