96 



boulder clay until it is found in the stream way, may have 

 been more numerous than the three above-mentioned, but 

 I have not found evidence of any others during a long period 

 of attention given to the subject. 



In the annexed cuts, the letters are in a sequence, and 

 it will be seen that in Fig. C, a considerable denudation 

 has removed the layers c, d, e, and f, of Fig. B, together 

 with T. ii., while T. iii. comes in, in a stratum not attain- 

 able at present in Rutter's pit. 



The upper or latest layers of Trail, represented in 

 PL ii. Jig. 4. as [T.] and in most of my figures, is not found 

 in its boulder clay stage, as it was formed when all the 

 present surface of the Brick-earths was dry land. Since 

 the deposition of T. ii. and T. iii., which are nearly 

 parallel, and generally conformable with the layers of 

 Brick-earth, a great denudation had occurred, and the 

 latest, T., cuts the others oif after the manner represented 

 in Jig. D., which diagram is an ideal section of this part of 

 the Old Darenth beds, shewing the denudation which has 

 cut off T. ii. and T. iii., and the different slope of T. com- 

 pared with the others. 



The upper or [T.] trail has cleared large quantities of 

 the fossil-bearing layers away, and deposited them in the 

 gravels now lying . in the Thames bed ; from which frag- 

 ments of bone, tusks and large molars of Elephant are 

 occasionally dredged in a condition which clearly shews 

 their origin. 



At Erith, large masses of Thanet Sand, Oldhaven, 

 and Woolwich shell beds with London Clay have been 

 pushed over the cliff edge. [Some of the great blocks 

 of stone may be seen now]. Mr. Tylor* expressed a 

 difficulty in accounting for this, and Mr. W. Whitakerf 

 speaks of it as a landslip. But I see no diflEiculty in 



* Quaternary Gravels, O. J. G. S., XXIV. 



t W. Whitak'er, Memoir of the Geological Survey. The London 

 Basin. 



