Reviews — Geological Survey of Great Britain. 467 



of unconformity locally exists. Some modifications have been found 

 necessary in the groupings of the strata classed as Millstone Grit and 

 Lower Coal-measures, and an unconformity has been proved at the 

 base of the Upper Barren Coal-measures in the Denbighshire district. 

 In Lanarkshire evidence of unconformity in the Millstone Grit has 

 been observed. A large tract near Tamvyorth, regarded on the old 

 geological survey maps as Keuper Sandstone, has now been ascertained 

 to consist of the Keele Beds or Upper E,ed Coal-measures. Some 

 questions concerning the upper limit of the Keele Beds have yet to 

 be solved. 



Notes are contributed on the Lias and Cretaceous rocks of Mull 

 (West Highland district), and particulars, illustrated by three maps, 

 are given of the Tertiary igneous rocks. The discovery is recorded 

 of numerous small hexagonal plates of blue corundum (sapphire), 

 with other minerals, in an igneous matrix that consists of andesitic 

 felsite and trachytic grandphyre or syenite, with included blocks of 

 baked sandstone and shale. 



In the London district the transitional clays, loams, and sands, 

 between the mass of London Clay and the Lower Bagshot Sand, have 

 been separately mapped as the " Claygate Beds", Descriptions are 

 given of the glacial and later drift deposits in the various districts. 



In the Appendices there is a short article "On some Palaeolithic 

 Gravels near Swanscombe, Kent ", by Mr. Reginald Smith (of the 

 British Museum) and Mr. Henry Dewey (of the Geological Survey). 

 They give results of a careful personal study of the successive 

 Pleistocene deposits in the Barnfield Pit, about half a mile north-west 

 of Swanscombe Church. Here, resting on the Thanet Sand, the top 

 of which is about 90 feet above O.D., is a series of gravels, sands, 

 and loams, about 25 feet thick, that are usually described as forming 

 the 100 foot terrace. Por about three weeks the authors employed 

 two gangs of men, and examined every spadeful of material dug 

 away in order to ascertain the nature and sequence of the flint 

 implements. Their results may be summarized as follows : — 



Upper Gravel . . Several flakes and one good implement, " but further 



evidence is required as to the horizon." 

 Upper Loam . . Said to contain white patinated ovates. 

 Middle Gravel . . More advanced forms, with one or two ovates of 



St. Acheul character. Paleolithic implements of 



Early Chelles type. 

 Lower Loam . .No implements. 

 Lower Gravel . . Numerous flint flakes and some roughly cylindrical 



flints chipped at one end into a point or chisel-edge. 



Comparable with the Belgian type named after 



Stripy in Dr. Eutot's system. 



It is regarded as not improbable " that the Middle Gravel represents 

 the whole of the Chelles period and the transition to St. Acheul ". 



Records of borings at Lowestoft, Henlow in Bedfordshire, and 

 Batsford in Gloucestershire, are communicated by Dr. A. Strahan. 

 Those of Lowestoft and Batsford are specially important. At Lowestoft^ 



^ Boring commenced 1902, not 1912. 



