362 Notices of Memoirs — The Geological Survey. 



quarter-sheet, for mucli reduplication of geological information 

 would thereby be involved. Several quarter-sheets or sheets may 

 be described together in a single Memoir. 



Occasionally these Memoirs, M^hen dealing with an important 

 district, have been expanded beyond the limits of mere Sheet 

 Explanations, and have taken the form of octavo volumes. Such, 

 for instance, are the Memoirs on the Yorkshire Coalfield, on North 

 Wales, on the geology of the Weald, on the geology of London, on 

 the Isle of Wight, and on Cowal, Argyllshire. 



The chief literary work on which the staff of the Survey is now 

 engaged is the preparation of the General Memoirs to which the 

 Sheet Explanations were designed to be preparatory. It appeared 

 to the present Director-General that these Memoirs should consist of 

 two series. In the first place, it is desirable that the local details 

 which remain unpublished, or which have been scattered through 

 separate Explanations, should be collected, condensed, and arranged 

 so as to present a description of each important district of the 

 country. As examples of this mode of treatment, the volumes on 

 the Weald, London, and the Isle of Wight may be referred to. In 

 the second place, it is obviously necessary, in the interests of 

 geology, that tlie contributions made by the Survey to that science 

 should be systematically set forth, and that a full account should be 

 given of each of the geological formations of which the framework 

 of the British Isles is built up. To carry out this requirement 

 a stratigraphical rather than a geographical treatment is needful. 

 A series of Monographs is demanded devoted to the description of 

 the various rock-systems of the country, and brought up to the time 

 of publication by giving not only what has been done by the Survey 

 but an outline of the work of other observers. 



The information obtained by the Survey in its progress is 

 necessarily scattered through many maps, sections, and memoirs. 

 The work of the service would be incomplete and difficult of 

 consultation if it were left in this disseminated state. It needs to 

 be gathered together, arranged, and put into connected form, so as 

 to present an intelligible account of the geology and mineral pro- 

 ducts of these Islands. The task is a heavy one and cannot be 

 speedily finished ; but satisfactory progress is being made. A Mono- 

 graph on the Pliocene deposits of England in one volume, and 

 five volumes of another on the Jurassic rocks, have already been 

 published ; one on the Upper Cretaceous rocks is far advanced, and 

 others are in preparation. Each Monograph will embrace one 

 system or group of rocks, and may consist of one or more volumes 

 according to the importance of the system and the area which it 

 occupies in the country. 



In the preparation of the memoirs, and for museum purposes, much 

 assistance is now derived from photography. Several members of 

 the staff have become expert photographers, and a large number 

 of views of geological sections, coast-cliffs, and other natural or 

 artificial exposures of rock have been taken. These serve as 

 illustrations fur the memoirs, and some of them are mounted to 



