4S 



STRATA IN THE N.EIGIIBOURHOOO OF LONDON. 



light ar dark, and sometimes inclining to agieenish tint, is 

 evidently derived from an ioipregnation with iroi>» Fvota 

 this impregnac ion they have nlso received a 2;veat increase 

 of wei^^ht and soiidity; from having been rolled they have 

 acquired a considerable polish ; and on being struck by any 

 hard body they give a shrill ringing sound. These frag- 

 ments, washed out of the stratum in whieu they had been 

 imbedded, are found on th« beach at. Walton, but occur in- 

 much greater quantity at Harwich. 



partrf* tooth Of the flat rounded pieces described above, no conjecture 



of-^wtjx- Ql^^^^ jj^ formed as to the particular bone, or particular ani- 

 mal, to which they belonged. But within tiicsefew years- 

 an Essex gentleman found, on tlie beach at Harwich, a 

 tooth, which was supposed to have belonged to the nicm-.. 

 moth. This fossil was kindly obtained at my request, for the 

 purpose of being exhibited to the members of the Geological 

 Society, by my late friend Dr. Tvlenish ; and certainly it 

 appeared to be part of a tooth of that animal. It had been 

 broken and rounded by rolling, but its characters were still' 

 capable of being ascertained. It possessed, in the softer 

 parts, the colour and appearance of the Essex mineralised ■ 

 bones so distinctly, as to leave not a doabt of its having, 

 been imbedded in this stratum ; while in the enamel it ma- 

 aifested decided characters of the tooth of some species of 

 the mammoth, or mastodon of Cuvier. 



Extent of tfels The actual limit of thisistratum has not been ascertained ; 



ttiat..iTr. -^ -g jjowever known to extend through Essex, Middlesex, 



part of Kent, and Surry, and through Hertfordshire, 

 Buckinghamshire, and indeed much farther both to the 

 northward and westward, lu many parts its continuity has 

 been interrupted, appareiitly by partial abruptions of jt^ 

 together even with a portion of the stratum on which it rests. 

 The shells of this stratum have hitherto been discovered: 

 only hi the parts already noticed. 



Blue clay siTalum. 



Blupcfay Tills, tiie next subjacent bed, is. formed of a ferruginous 



stratum. ^.l.Jy exceeding two hundred feet in tliickness. Its colour 



- for a ffc'W feet in the upper part is a yellowish *brown, but' 



through the whole of its remaining depth is of a dark bluish 



grny, 



