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Explanatory Notes E ! P L A N A T O R Y N O T E S TO AC C OM PAN Y A N EW G EOL OG IC AL M AP ENG LAND £5 W ALES AR H B AL D G E K E D F R S IR C . C . I I I , S . S D ir ec to r Gen e r al of t he Geo lo g ic al S u r vey J OHN BARTHOLOM EW 8: C O. (t h e E b in b u rg b G e o g raph ic al an s t it u t e 1 897 J H K A IH UNIV E RS ITY OF C AL I FORNIA SANTA BARBARA E! PLA N ATO RY N OTES TO AC C OM P A NY TH E G e o lo g ic a l M a p o f E n g la n d a n d W a le s I N C E the appearance in the year 1 8 1 5 of the first general E geological map of ngland and Wales, by William n an d Smith , umerous maps of the whole of parts of the a coun try on various scales have been published. The e rliest . G of these, by G B . reenough, was begun while that of William a r f —in Smith was in prepar tion , and appea ed our years later 1 8 1 9 . It passed into the hands of the Geological Society of . London , has from time to time been improved, and is still on sale . Its topography, however, compiled and engraved in the early part of the century, was from the beginning imperfect, a and its geology has been so repeatedly and extensively ltered . that its later forms bear only a general resemblance . to the 1 8 ori inal . The Geological Survey, begun in 3 , has g 5 _ now completed the mapping of the whole country on the scale of ' c e o n On e in h to a m ile, and is issuing a r duction the scale of ' All a re four miles to one inch . general m ps now prepared a ffi c . In 1 8 l based on the sheets of this o ial survey 59, the ate R Sir A . C . amsay, then Local Director of the Geological a e E n Survey of Great Brit in , publish d a general map of ngla d and Wales on the scale of twelve miles to an inch. It was a reduction from the Survey maps as far as these had at the time u c i ‘ ditio n s has d . s c e ss ve e been publishe In it been improved, ' t h st ee e . be i and up till now it has b n available map , but ts 4 G E O L O G I C A L M A P OF E N G L A N D A N D W A L E S topographical basis was too inaccurate for the production of a wholly satisfactory representation of the geology . a Five years ago, Mr. Bartholomew, who had with great l bour constructed from the she e ts of the Ordnance Survey a general topographical m ap of E ngland and Wales on the scale of ten miles to an inch , expressed to me h is willingness to employ the u c same plates for the prod ction of a geological map of the ountry, if I would supe rintend the reduction from the published maps of the Geological Survey . His map is so good as a general Of topographical representation the country, that it appeared to me likely to prove convenient and useful if the geology were inserted on it . Accordingly, his proposal was eventually carried f into e fect , and the map so prepared is now issued to the public . ’ a While the reduction has been made by Mr . B rtholomew s able assistant , Mr. Bosse, it has been repeatedly revised by some of a my colle gues in the Geological Survey, as well as by myself. a a The late Mr. W . Topley, took l rge share in the early u stages of this labo r, and since his death the task has been carried on by Mr . H . B . Woodward , Mr. W . Gibson , a and Mr . W . W. Watts . I have dr wn the Sections which are place d round the borders O f the m ap to explain the geological structure of the country . The following brief Notes are intended merely for the general reader or traveller who may have no special geological w a kno ledge, but may be induced to t ke the map with him as a convenient guide in !ourneying across the country . The meaning of the various colours and the n ature of the rocks they represent are here briefly explained . A cursory glance at a geological map of E ngland and Wales reveals some of the fundamental features in the geology of the . : country I n the first place, it shows that a line drawn in a nearly north and south direction from the coast of Durham“ about the mouth of the Tees, to that of Devon , at the mouth E x e a of the , divides the region into two p rts . To the west of i r i that line the colours are d st ibu ted . n patches Of widely dif fe ren t . TO sizes, and apparently scattered at random the east, e . i on th e other hand , the s veral tints are disposed n bands which follow each other continuously across the island from r E the sho es of the North Sea to those of the nglish C hannel . In the western half of the country the rocks belong mostly to ' Th h the Palaeozoic formations. ey ave generally been greatly disturbed, many of them having been plicated , crumpled, and E X P L ANAT O R Y N O T E S 5 a a squeezed . For the most part they consist of harder m teri ls than those to the east of them . Hence, partly owing to their ' a u rabilit y gre t er d , and partly to the influence of their disturb e . an cs and upheavals , they rise into the highest tracts of ground n Begin ing on the north , and tracing the series of older rocks e from the Scottish Border to Devonshir , we pass successively over . the hills of the Lake Country , the Pennine Chain , Wales , and Dartmoor, and we note that these eminences usually form a detached groups, such as those of Cumberland, Westmorel nd , W and North ales. I n the eastern half of the island, on the other hand, the rocks are arranged in successive bands which present their edges towards the west , and sink below each other towards th e the east. The harder members of series, such as lime stone and sandstone , rise into long ridges , while the softer clays, marls, and shales subside into valleys or spread out into plains . The hills are not only less lofty than those of the western side, but they are further distinguished by their prolongation into continuous ridges . The most familiar examples of this type of sc enery are supplied by the chalk hills. Thus the North Downs, which run for many miles ’ c lifls westward from the Dover , mark the trend of the chalk through that part of the country, while the corresponding range of the South Downs reveals the long unbroken outc rop a of the same rock from Beachy Head to Salisbury Pl in . ' It is thus evident that the landscapes of the country depend for their character mainly upon the nature and dis t ribu tio n of the rocks underneath the surface . The traveller or tourist who !ourneys with a geological map in his hand can mark how each distinct ch ange in topography arises from a corresponding alteration in the character of the geology . The variations of scenery consequently acquire for him a n e w mean ing and interest . There is no part of Europe where the relation E here described can be better seen than in England . ven from a rapid railway !ourney much may be learnt here regard e ing the depend nce of topography upon geological structure . In the second place, a little closer study of the map will O show us that , on the whole , the ldest rocks lie along the western shores, and the youngest along the eastern . If we were to land in Anglesey and traverse the country to the coast of ff Su olk , we should pass successively from some of the most ancient formations of Britain to some of the newest, as is illus - At t rate d by the section on the left side of the map . Holy 6 G E O L O G I C A L M A P O F E N G L A N D A N D W A L E S head we should find ourselves among quartzites and schists of higher antiquity than even the most ancient of the Palaeozoic n formations , which further south , in Anglesey, are fou d resting C ae rn ar on the edges of these primeval rocks . Crossing into vo n sh ire O , we should come upon some of the ldest st ratified o a a dep sits in the country, belonging to the C mbri n system , an d from these, ranging into the great cone of Snowdon , and a thence into Montgomeryshire, we should sce nd in the geo o f logical scale through the vast thickness the Silurian system , l up to the base of the O d R e d Sandstone .
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