The Worlc of the Geological Survey. 
159 
of the Geological Survey of the United Kingdom. The form in 
which these publications have appeared has varied. De la Beche’s 
plan was to publish volumes of General Memoirs embracing descrip- 
tions of particular regions, and also essays on special branches of 
geological inquiry. His own memoir on the geology of Cornwall, 
Devon, and West Somerset is an admirable example of his method, 
and has long taken its place among the classics of English geology. 
There were practical difficulties, however, in the way of continuing 
his method when the staff increased, and the literary labour had to 
be shared by a number of observers, who were, in many cases, 
more willing to wield their hammers than their pens. When 
Murchison succeeded to the charge of the Survey, he sought to 
avoid these difficulties by instituting the practice of accompanying 
every sheet or quarter-sheet of the 1-inch map with an explanatory 
pamphlet, giving the chief data on which the map had been con- 
structed, with references to the best sections, lists of minerals and 
fossils, and information as to the geological structure of the ground. 
These pamphlets, containing essential details only, were to be even- 
tually condensed and collated by the Local Director, so as to form 
a generalised view of each important geological region. This scheme 
was well conceived, and with some modifications rendered necessary 
by the progress of the Survey, has been carried out ever since. It 
is not always possible or desirable to prepare a separate explanation 
for each sheet or quarter-sheet, for much reduplication of geological 
information would thereby be involved. Several quarter-sheets or 
sheets may be described together in a single Memoir. 
Each surveying officer is expected to contribute the account of 
the area mapped by him. Where more than one surveyor has been 
engaged on a map or district, the accounts furnished by the several 
officers are collated and edited in the office, and are published gene- 
rally in paper wrappers and at a low price. 
Occasionally these Memoirs, when dealing with an important 
district, have been expanded beyond the limits of mere Sheet 
Explanations, and have taken the form of thick octavo volumes. 
Such, for instance, are the Memoirs on the Yorkshire coal-fie.d, on 
North Wales, on the geology of the Weald, on the geology of 
London, and on the Isle of Wight. 
The chief literary work on which the staff of the Survey is now 
engaged is the preparation of the General Memoirs or Monographs 
to which the Sheet Explanations were designed to be preparatory. 
It appeared to me that the most generally useful plan on which 
these could be prepared was to make them fundamentally strati- 
graphical — in other words, to devote them to a description of the 
various geological systems which are embraced within the British 
Isles, and to show not only what has been done by the Survey in each 
of these systems, but what has been ascertained by others. Each 
Monograph should thus be a compendium of all that is known of its 
subject up to the date of its publication. 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 
