232 Reviews — Memoirs of the Geological Survey. 



from the coast of the French colony of Gabun. The specimens 

 here described are all volcanic, belonging to eruptions of different 

 ages, but showing distinct features of consanguinity. In general 

 terms it may be said that all belong to the alkalic and peralkalic 

 volcanic groups. They include types described as pbonolites, 

 containing nepheline and hauyne, and in one case plagioclase ; 

 phonolitic andesites with hornblende or pyroxene, hornblende- 

 trachyandesites and camptonites ; trachydolerites and alkali- 

 basalts passing into limburgites ; nepheline-basalts, tephrites, 

 limburgites, and augitites. Descriptions of all these varieties are 

 given in detail, illustrated by good microphotographs. The most 

 common type is basalt, especially in the north-east of the island. 



The most interesting feature of the island is a " spine " of the 

 Pelean type, called the Cao Grande, of which an excellent photo- 

 graph is given. Not far from it is found a smaller example, the Cao 

 Pequeno, and on the slopes of the 16 Grande, there are said to be 

 other examples. 



The petrographical character of the island approximates to 

 that of the other volcanic islands of the Atlantic, from the Canaries 

 to Ascension, and shows close relations with the neighbouring 

 volcanic regions of the African continent. 



E. H. R. 



Memoirs of the Geological Survey of England and Wales. 

 By Henry Dewey and C. E. N. Bromehead, B.A. Sheet 270, 

 SouthLondon. pp. vi-)- 92, 3 plates, and 1 text-figure. 1921. 35. 

 Map. Sheet 270, South London. Drift. Colour printed. 2s. 

 rpHE map covers substantially the same ground as the south- 

 -^ eastern sheet of the special London district map published 

 in 1903. The area was, however, resurveyedjust before the war on 

 the 6 in. scale, and the new map is based on this survey. New 

 features in the map are the separation of the Claygate Beds from 

 the London Clay and an alteration in the subdivisions of the super- 

 ficial deposits. Considering the denseness of buildings in the area 

 and the somewhat complex symbols used to denote the older 

 superficial deposits, the map is extraordinarily well j)rinted and clear,, 

 and a welcome change from the illegibility of the new map of 

 Anglesey. 



With regard to the memoir, a considerably more detailed account 

 of the area is given than that in H. B. Woodward's Geology of the 

 London District (1909), of which a revised edition is soon to be 

 published. The first alteration of importance is the introduction of 

 the term Claygate Beds, proposed by Dewey in 1912. These beds 

 are the uppermost 50 feet of the London Clay, and are practically 

 unfossiliferous. They differ lithologically both from the London 

 Clay and from the Bagshot Beds. They are conspicuously even- 

 bedded, with beds of clay and sand, the latter increasing in thickness 

 upwards. The sand is of much finer grain than is usual in the 



