12 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 20, 



fore more rapid ; the beds of lignite becoming more and more irre- 

 gular, and separated by coarser and coarser materials. At length, 

 as the sediment approached the surface, the lignite ceased to be de- 

 posited ; the specific gravity of the trees not being sufficient to with- 

 stand the current ; and very rough granitic gravel was alone allowed 

 to become fixed. 



Fig. 2 is a section across the beds of pipe- and potter's clay, on 

 the eastern side of the basin, near New Cross. It is constructed on 

 data obtained from the inspection of deep and shallow pits from 

 Knighton to T^ewton-marsh, from reports of the workmen, from 

 borings, and from the superintendence of the Newton-marsh Claj- 

 works. This section will nearly represent the stratification of the 

 continuous clay-deposit from near Knighton, on the north, to the 

 Newton Railway Station ; with this difference, that at the com- 

 mencement of the deposit the seams of fine clay are thin, somewhat 

 irregular, and to some degree mixed with quartz -gravel. The dip 

 is also greater than in the section ; and in several places the clay- 

 beds show the action, apparently, of running water, portions of the 

 fine material having been evidently washed away, so that the fine 

 clay runs down to a considerable depth almost perpendicularly. 



From Knighton southwards the beds of fine clay increase in thick- 

 ness, purity, and regularity to below New Cross, where they begin 

 to diminish in thickness, until lost south of the Newton Railway 

 Station. In two or three places narrow bands of coarser clay, 

 generally stained, run across the finer clay ; and in several places 

 the pipe-clay forms two beds. 



Fig. 3 represents a section of the beds of clay, &c., at the Decoy*, 

 and has been constructed from numerous observations made at the 

 spot and in its vicinity during ten years. All the seams of clay shown 

 in the section have been worked for considerable distances longitudi- 

 nally, from 60 to 100 feet transversely, and to depths of from 30 to 90 

 feet. The inclination of the strata here is much greater generally 

 than, and in the opposite direction to, that in the section fig. 2. It 

 will be observed, however, that the superposition of the beds is 

 almost identical with that in the last-mentioned section, taken 

 in the upper part of the basin : the pipe-clay, it is true, is divided 

 into three distinct beds, against two in section fig. 2 ; but the order 

 of deposition is the same, and the description of one would suit the 

 other. Taking the beds in order upwards, we shall have rough 

 clays, pipe- clay, stiff clay, dark fine clay, rough muddy clays, pot- 

 ter's clay, and lignite. In section fig. 2, there are two beds of 

 potter's clay shown ; at the Decoy also there is to the east a small 

 second scam of fine clay resting on the one shown in fig. 3. 



Several seams of lignite, almost perpendicular in dip for the first 

 15 or 18 feet from the surface, and separated by thin divisions of 

 dark clay and vegetable matter, lie immediately below the bed of 

 potter's clay in fig. 3. 



The pipe-clay at the Decoy has been worked about 90 feet deep, 



* This is the " deep watercourse below Woolborough," in Mr. Godwin-Austen's 

 Memoir, Geol. Trans. 2nd ser. vol. vi. p. 451. 



