ANNIVERSARY ABDRESS OF THE PRESIDENT. Iv 



true scale both vertically and longitudinally, may help to clear up 

 the still vexed question of the denudation of the Weald. 



The mapping of the Lancashire Coal-field and adjoining areas is 

 so far advanced that it is expected to be finished by the close of this 

 year ; and the coal-fields of Yorkshire, Newcastle, and Durham are 

 also being mapped, and parts of them are already published. The 

 Survey has also begun to make some progress in the exceedingly 

 difiicult country forming part of Westmoreland and Yorkshire near 

 Kendal and Kirkby Lonsdale — a country complicated by great con- 

 tortions of the Silurian strata, by numerous large faults, and by the 

 concealment of the Silurian Old Eed Sandstone and Carboniferous 

 rocks by drift ; and it is hoped that a beginning will soon be made 

 to the issue of the geologically coloured maps of the district. 



A large tract of Ayrshire has also been surveyed, consisting of 

 Silurian Old Red Sandstone and Carboniferous rocks; and the finished 

 maps are now in the hands of the engravers. 



By way of showing the usefulness of these documents to the public 

 I may mention that, in his Annual Report, Sir Roderick Murchison 

 states that during the last ten years more than 36,000 maps and sec- 

 tions of the Geological Survey of Great Britain have been sold, not in-^ 

 eluding, of course, the large numbers given away to learned societies. 



The only memoir published by the Survey during last year is that 

 on the Geology of North Wales, by Professor Ramsay. It commences 

 in the 1st and 2nd chapters with an historical account of the nomen- 

 clature employed in regard to the formations of which the Silurian 

 series of Britain consists, and sketches their extent and physical rela- 

 tions all through Wales and Shropshire. The remainder of the 

 descriptive geological portion of this volume is occupied with a minute 

 analysis of the structure of the Silurian region of North Wales ; and 

 to render this as clear as possible, besides the coloured plates of a 

 map and sections, ninety-nine woodcuts are introduced, mostly illus- 

 trative of the physical relations of the rocks all over the country ; and 

 it is thus intended that by reference to the book any one may find 

 enough of illustrative matter to enable him to understand the geological 

 structure of almost every hill and valley in North Wales occupied by 

 Silurian rocks. A brief sketch of the surrounding later formations is 

 also given. The relations to each other of the igneous and stratified 

 rocks of this remarkable region are explained according to the views 

 held by Professor Ramsay and his colleagues on the Survey, views in 

 the main held by the late Sir Henry De la Beche. It is shown, in 

 accordance with these views, by the help of numerous sections, that 

 the felspathic rocks consist to a great extent of intrusive bosses, and of 

 great sheets of lava and of consolidated volcanic ashes on two horizons — 

 one at the base of the Bala beds (Llandeilo), and the other on the hori- 

 zon of the Bala limestone. These have been disturbed and faulted, 

 thrown into anticlinal and synchnal curves, and denuded on a vast 

 scale, whence arises the present physical configuration of the country, 

 the hard rocks generally forming hills and mountains, and the softer 

 slaty beds being apt to lie in valleys. Certain of the terms thus employed 

 involve an assumption as to the origin of the alleged volcanic sub- 



