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XIX. 
THE GRAVELS OF HERTFORDSHIRE. 
By A. E. Salter, D.Sc., E.G.S. 
(Communicated by J. Hopkinson, F.L.S., F.G.S.) 
Read at Watford , 2nd November , 1904. 
Introduction. 
The superficial deposits of Hertfordshire have been made the 
subject of study by many geologists, and papers relating to them 
by Professor T. McKenny Hughes,* 4 Searles V. Wood, jun.,f Sir 
Joseph Prestwich, J J. V. Elsden, || H. W. Monckton and B. S. 
Herries, § Dr. A. Irving, Dr. T. E. Lones,* 4 * 4 H. B. Woodward,ff 
and the author, J J may be found either in your own ‘ Transactions ’ 
or in those of other societies. 
Most of these deal with parts of the County only. It is proposed 
in this communication to treat of the whole of the superficial 
deposits of the County, and to deal somewhat with that vexed 
question, their mode of origin. 
To account for these deposits one school of geologists would 
invoke the aid of marine conditions, while another would discard 
this utterly and refer their production to the action of ice-sheets or 
other glacial phenomena. 
It has always appeared to me that, before invoking the aid of 
these all-powerful agents upon what is often very meagre or 
untrustworthy evidence, it should first be ascertained to what 
extent many of these deposits may be due to the ordinary agents of 
denudation, acting perhaps at times with greater or less intensity 
than in the present day. Having eliminated all such deposits as 
may reasonably be referred to this cause, we should then perhaps 
be in a better position to gauge the truth or falsity of the hypotheses 
* “ On the two Plains of Hertfordshire and their Gravels,” ‘Quart. Journ. 
Geol. Soc.,’ vol. xxiv, p. 283. 
t “On the Pebble Beds of Middlesex, Essex, and Herts,” ‘Quart. Journ. 
Geol. Soc.,’ vol. xxiv, p. 464. 
+ “On the Relation of the Westleton Shingle to the other Pre-Glacial Drifts 
in the Thames Basin,” ‘ Quart. Journ. Geol. Soc./ vol. xlvi, p. 155. 
|| “The Post-Tertiary Deposits of Hertfordshire,” ‘Trans. Herts Nat. Hist. 
Soc.,’ Vol I, p. 103. 
§ “On some Hill Gravels north of the Thames,” ‘ Proc. Geol. Assoc.,’ 
vol. xii, p. 108. 
If “On the Geology of the Stort Valley,” ‘Proc. Geol. Assoc./ vol. xv, 
p. 224; see also ioc. cit., p. 193. 
** “The Gravels, Sands, Clays, and Loams of Western Hertfordshire,” 
‘Trans. Herts Nat. Hist. Soc./ Vol. X, p. 153. 
+f “ On Disturbances in the Chalk near Royston,” ‘ Quart. Journ. Geol. Soc./ 
vol. lix, p. 362; see also ‘Proc. Geol. Assoc./ vol. xviii, p. 167. 
++ “ ‘Pebbly Gravel’ from Goring Gap to the Norfolk Coast,” ‘ Proc. Geol. 
Assoc../ vol. xiv, p. 389 ; see also vol. xv, p. 274. 
VOL. XII.—PART IV. 
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