The Ancient Fauna uj Essex. 
1 9 - 
but it would be only local; considerable changes of level, 
for instance, have taken place in our own Thames Valley. 
Below high-water-mark, in the neighbourhood of Victoria 
and Albert Docks at Plaistow, there are abundant evidences 
of deposits such as I have spoken of, and a canoe has been 
found, showing that primitive man was there when the 
valley stood at a far higher level than now. Mr. Searles Wood 
in some of his papers mentions trees in situ at many points 
below the present level of the Thames, affording good evidence 
that in prehistoric times the level of the Thames stood con¬ 
siderably higher than it does now; and that savage men, if not 
civilised men, at that time occupied the country. 
Probably no independent geological investigator since the 
early days of Buckland, Trimmer, and Morris, has paid such 
careful attention to the structure of the Thames Valley, and 
of its contained deposits, as Mr. Searles V. Wood, F.Gf.S. 
Numerous papers on this subject have been communicated 
by him to the ‘ Quarterly Journal of the Geological Society’ 
and to the ‘ Geological Magazine.’ 
Writing thereon in 1866 (Geol. Mag., vol. iii., p. 59), 
Mr. Wood observes : “ The brick-earth of Ilford, both that 
of Uphall and that of the London-road Field, is a deposit 
underlying the Thames gravel, and unconformable to it.” 
He also speaks of it as anterior in date to the similar deposit 
of Grays, which likewise contained Cyrena fluminalis and 
other purely fresh-water shells. 
In a letter to me (dated March 10, 1874) Mr. Wood says :— 
“When I wrote the paper in vol. iii. of the Geol. Mag. (1866), 
I was under the impression that, though the Grays brick- 
earth was clearly newer than the main sheet of the Thames 
gravel (it forming distinctly a terrace beneath it), the Cyrena 
brick-eartli of Ilford, and of Orayford and Erith, was anterior 
to, and passed underneath, it. Some year or two afterwards, 
however, I satisfied myself that this was an error as concerned 
Crayf'ord and Erith, and I wrote a letter to the 4 Geological 
Magazine’ (Oct. 10. 1868, vol. vi., p. 534) directly, to ac¬ 
knowledge this. 
“ The Ilford bed lying flush with the gravel sheet of that 
part of Essex does not present the means of determination 
by section; but I cannot doubt, however, that it is identical 
