8 



succession which was hinted at in Mr Trimmer's last paper, and 

 indicated the distribution of the several divisions over the whole 

 of East Anglia ; he maintained that the main mass of the 

 Boulder Clay overlaid the Sands and Gravels which cap the. 

 cliffs along the Cromer coast, and that these therefore must be 

 distinct from the Gravels overlying the Boulder Clay in the 

 centre of Norfolk. Mr Wood however still continued to divide 

 the series into two groups, an Upper Drift and a Lower Drift, 

 the latter being again divided into an Upper and Lower series\ 

 The above-mentioned paper was withdrawn from the Geological 

 Society and privately published in 18G5, when he saw the 

 desirability of a more simple terminology, and proposed the 

 following : 



1. Upper Drift (= Upper Drift, 1864). 



2. Middle Drift (= Upper series of Lower Drift, 1864). 



3. Lower Drift (= Lower series of Lower Drift, 1864); 



Mr Wood's more recent views on the Glacial Series are pub- 

 lished in the preface to his father's Supplement on the Crag 

 Mollusca, which includes "An Outline of the Geology of the 

 Upper Tertiaries of East Anglia:" he here adopts the name of 

 Glacial beds in preference to that of Drift, and the various 

 divisions of the series are described in some detail according tO' 

 the ascending order given in the following classification. 



1. Pebble beds ..A 



2. Cromer Till ... > = Lower GlaciaL 



3. Contorted DriftJ 



4. Sands and Gravels = Middle Glacial. 



5. Great chalky Boulder Clay .... = Upper Glacial. 



6. Plateaux Gravel ) ^i ^ /-n • i 



« ^ . , ^^ ,, rN ^ t = Post Glacial. 



7. Estuarme and Valley Gravels) 



In 1863 Sir Roderick Murchison,then Director General of the 

 Geological Survey, decided, "that as the superficial drift deposits 

 attain a thickness so considerable in many parts of England 

 that they conceal the solid geological formations," it would 

 be desirable to publish special maps of these districts showing 

 the superficial deposits, and to re-survey certain areas in order 



1 Quart. Journ. Geol. Soc. Vol. xsi. p. lil, and Ann. Mag. Nat. Hist. 1864. 



