Vol. 55.] ANNIVERSARY ADDRESS OF THE PRESIDENT. Ixxix 



geology. The second, dealing with Berkshire, is being taken in 

 hand. 



In doing such work the Geological Survey is following in the 

 footsteps of its founder and first chief, Sir Henry De la Beche, who, 

 more than 50 years ago, carried out investigations of this sort, for 

 in 1845 the Health of Towns Commission published a work by him 

 entitled ' Report on the State of Bristol & other Large Towns,' of 

 which there is a copy in the Society's library.^ This deals with 

 Bath, Prome, Swansea, Merthyr Tydvil, and Brecon, giving a short 

 account of the geological character of the ground and of the water- 

 supply in each case, with a geological map and section for Bristol 

 and a map for Bath. 



For the proper consideration of questions of water-supply and 

 of other sanitary matters involving geological investigation, it 

 is essential that we should have maps in which the Drift is 

 shown. 



In 1863 Sir E,.]\Iurchison, then Director-General of the Geological 

 Survey, decided to have the Drift shown by colour on the 1-inch 

 maps of that Survey, the importance of the superficial deposits from 

 an agricultural point of view being then recognized, although their 

 greater importance for other practical purposes was probably not so 

 clearly understood. 



Unfortunately the importance of separating the various kinds of 

 Drift was not realized for some time, and the mapping was done on 

 the principle of lumping the whole, a proceeding that took away 

 most of the value of the record, though vastly expediting its 

 progress. After some time, the practical advantage of separating 

 gravel and sand from loam and from Boulder Clay was seen, and the 

 first map published with these divisions was that which includes 

 the western half of London and the Valley of the Thames upward, 

 to Henley, namely, Sheet 7, the Drift edition of which was issued 

 in December 1871. Since that time the work has gone on, not only 

 as regards maps in progress, but by the Drift being added to maps 

 already published. 



Useful as these maps may be, especially to those geologists 

 wishing to write papers on gravels, etc. (and they seem to have 

 been very fruitful in this respect), they are far from being adequate 

 for many practical purposes, for which a map on a much larger 

 scale is often wanted. The importance of such larger maps was 



1 Pp. 102 & 3 pis. 8vo. London. 



