322 



ME. F. W. HAEMER ON THE LENHAM BEDS [Aug. 1898^ 



zone A/ dividing the shelly sands between A and G, which have in 

 all a maximnm thickness of no more than 30 feet, into five zones : 

 B, C, D, E, and F. Whether we examine it chemically or micro- 

 scopically, however, we can find no essential diff'erence in the 

 material of which these several beds, B to F, are composed. It 

 is throughout mainly of organic origin, consisting of the com- 

 minuted shells of marine organisms or of calcareous matter derived' 

 from their decomposition, with only a small admixture of inorganie 

 ingredients. The proportion of the latter varies slightly in speci- 

 mens taken at different spots, as will be seen below. 



Mr. Francis Sutton, of JS'orwich, a well-known authority, has^ 

 kindly analysed for me some examples of the two varieties of 

 Crag, with the following result : — 



Shelly sands (No. 1) 



Ferruginous Crag (No. 2) 



Carbonate of 

 Lime 



78-62 o/o 

 78-95 o/o 



Silica 



7-750/0 

 11-50 «/o 



Oxide of Iron^ 

 and Alumina 



3-50 «/o 

 7-20 Vo 



More recently his son, Mr. W. Lincolne Sutton, the public analyst 

 to the Corporation of Norwich, has tested some fresh samples, and' 

 reports as follows : — 



Carbonate of Oxide of Iron 

 Lime Silica and Alumina- 

 Shelly sands (No. 3) 70-9 «/^ 13-5 «/o 7-1 0/0 



„ (No. 4) 74-7 «/o 12-8o/o 5-5o/o 



Ferruginous Crag (No. 5) 79'2% 11*4 0/0 4-2 % 



Dr. G. J. Hinde, F.E-.S., has been good enough to examine- 

 samples 3 & 5 for me microscopically, and says : ' Under a low 

 power or with a hand-lens the Crag is seen to contain, as is well 

 known, specimens of foraminifera and entomostraca, fragments of 

 mollusca and polyzoa, and the spines of echinoderms, with grains 

 of quartz, some angular, others rounded, and dark green granules 

 of glauconite, rounded and polished. Among the finer material I 

 find an immense number of minute almond- or diamond-shaped 

 calcspar-crystals, amorphous particles, and coccoliths, and numerous 

 rod- like bodies, simple or branching, usually vermiform ' (see fig. 2) ; 

 these he considers may be ' the solid infillings, by a silicate of iron, 

 of borings in moUuscan shells by the action of organisms supposed 

 to be of the nature of algae or fungi. They are not seen until the- 

 shells have been dissolved by acid, are translucent, and polarize 

 feebly. Numerous coccoliths are present, somewhat larger than 

 those in the Upper Chalk, and I do not think that they have 

 been derived from that formation. It is important to notice that 

 only two microscopic chips of flint were observed, with perhaps an 

 occasional flake of mica and a grain of felspar.' 



^ Tne Dasemenc-bed, zone A of Prestwich, is, of course, of a different 

 character, originating under conditions dissimilar to those of the rest of the Crag,. 



