GEOLOGY. 



GEOLOGY. 



Wcalden System : 



18. Weald clay . 



19, Hastings sand . . . 

 20 Purbeck beds 



Oolitic System : 



[11. Portland stone . . . 



a. Limestones with clay and 



cherty bands 



b. Siliceous ?and . . . 



22. Kimmeridge beds 



f 23. Coral rag and calcareous 



; grits . ... 



24. Oxford clay . 

 a. Stiff clay . . . . 

 6. Kelloway's rock . 



f25. Cornbrash . . . 

 20. Forest marble 

 27. Bradford clay . . . 



23. Great oolite 



. Stoncsncld slate . . 

 30. Fullers' earth 



1. Inferior oolite . . . 

 Liassic System : 



32. Alum shale . 



33. MarUtone . . . 



34. Lower lias . . . 



35. White lias . . . 

 l"pt>er New Red. Sandstone, or 



Ti lassie System : 



36. Bone-bed of Aust Cliff . 



37. Variegated marls, with 

 salt and gypsum . 



38. Variegated sandstones . 



Near Boulogne. 

 North of Germany. 



Jura limestone is the usual continental 



synonym of our oolitic series. 

 Lithographic limestone of Blangy. 

 Uonnenr clays. 

 Solnhofcn beds. 

 Beds itt South of Russia and in India. 



Nerincan limestone. 

 Argilc de Dives. 



Etagc Bathonien id the name given by 



D'Orbijrny to our lower oulites. 

 Calcairc u polypiers. 

 Calcairc dc Caen. 



Calcairc a gryphites. 



Kcupcr marls, or Marncs irisccs. 



Muschclkalk. 



Bunler sandstcin, or Gics bigarrc. 



Zcchstein. 



Kupfcr Scltiefer and other shales. 



llothe-todtc-licgcnde. 



PALJSOZOIO EPOCH. 



Magncsian Limestone, or Permian 

 System : 



39. Magncsian limestone . 



40. Dolomilic conglomerate . 



41. Lower new red- sand- 

 stone .... 



Carboniferous System : 



The coal-measures occupy an important 

 place in various parts of the continent, 

 in Belgium, France, the Rhine, South 

 KH-M;I, and also in North America ; in 

 various parts of Asia, and in Australia. 

 The foreign synonyms are, Stcinkohlen- 

 (rebirge, terrain houillier, terrain car- 

 boniferc, and terrain anthraxift-re. 



The millstone grit is generally a bed of 

 subordinate importance out of the 

 British Islands. 



The Kicscl Schiefcr of Germany is an 

 equivalent of the carboniferous lime- 

 stone. 



The Belgium limestone beds and others 

 in Northern Bavaria are in the same 

 part of the series. 



42. Coal measures . . 

 ft. Gritstones . . . 

 6. True coal-measures 

 c. Fresh-water limestone of 

 Ourdic House, near 

 Edinburgh . 



43. Millstone grit . . . 



n. Coarse griutones . 



(/. Laminated shales 

 11. Carboniferous limestone 



a. Bands ot fossiliferous 

 limestone . 



4. Shales (calp, culm) . . 



Devonian, or Old Kcd-Sandstone 



45. Quartzosc conglomerates 

 (old red -sandstone) 

 in South Wales and 

 Scotland ; represented 

 by coarse red flag- 

 stones and slates in 

 Devonshire and Corn- 

 wall .... 



in. Cornttonc and marl of 

 the old red.sandstore. 

 Calcareous slate, lime- 

 stone, sandy beds, and 

 conglomerates of De- 

 vonshire and Cornwall. 



Upper Silurian Series : 



17. Tilcstonc . ... 



48. Lndlow group . . 

 , a. Upper Ludlow shales 



b. Aymcstry limestone . . 

 r. Lower Lndlow shales 



49. Wenlock group . . 

 a. Wcnloek limestone 



6. Wcnloek limestone . ' . 



Devonian teds arc well known in Belgium, 

 the Eifcl, Westphalia, and North Ba- 

 varia. In Russia the old red-sand- 

 stone appears, and contains similar 

 fossils to those found both in the 

 corresponding beds in the British 

 Islands, and also in Devonshire and 

 Herefordshire. The palco/.oic beds of 

 Australia are supposed to be contempo- 

 raneous. 



" Silurian strata extend over much of the 

 northernmost parts of Europe, and cor- 

 responding latitudes in America. They 

 have been found in Brittany, in West- 

 phalia, near Constantinople, and in Asia 

 Minor. In South Africa, the southern- 

 most parts of South America, Australia, 

 and China, different contemporaneous 

 rocks have been determined. In 

 mineral character they are generally 

 distinct from the English beds, but 

 offer no marked characters uniformly 

 present. 



Lower .Silurian series : 



50. Caradoc sandstone . . 



51. Llandeilo flags 



We may now turn to the consideration of the present aspect of the 

 globe. 



According to every view of geological causes and effects, the 

 present aspect of our planet is the result of all its previous changes ; 



these changes cannot be completely understood if we leave out of 

 consideration the daily variations which occur in the condition of the 

 earth, nor can the operation of existing agencies be completely repre- 

 sented to our minds without calling in aid the inferences derived from 

 a study of earlier phenomena. 



One of the most important things ascertained by geological 

 investigation is the certainty that the operations by which stratified 

 rocks wero formed in the sea-bed, and the igneous rocks uplifted 

 from below, were repeated nearly in the same succession over most 

 parts of the globe. Some of the formations are very extensive : in 

 all countries the lower strata are of the character of gneiss, mica- 

 schist, slate-rocks, &c. These primary strata may almost be termed 

 universal: the organic forms which they contain, though few, are 

 very similar, or exactly identical, over enormous areas ; and there can 

 be no doubt that during the deposition of these ancient rocks the 

 earth enjoyed an uniformity of conditions over its surface never since 

 repeated. There is no proof that laud existed anywhere in the earlier 

 part of this period no probability that any part of our continents 

 or islands then stood above the water. At the close of the primary 

 period the eS'ect of elevatory forces was manifested by the existence 

 of some narrow ridges and peaks of rocks, corresponding to some of 

 our present mountain tracts, as the Grampian and Cumbrian moun- 

 tains, and of others now vanished, which nourished the forests and 

 herbs whose destruction has yielded coal. 



Through the secondary period this elevation of land proceeded 

 gradually, or by intermitting action, till at the close of that period 

 some of the principal features of European geography were visible ; 

 the ocean was contracted and divided into many basins and gulfs, 

 some of which remain, as the Adriatic, English Channel, German Sea, 

 &c. ; while others, as the Vale of the Danube, Sea of the Khiue, &c., 

 have been dried by further elevation. 



The same elevatory action continued through the tertiary eras 

 completed the geographical features of Europe, and though we cannot 

 trace so minutely in other parts of the world the contemporaneous 

 changes, enough is known to a:>sure us that the same causes have, 

 within the same general limits of time, produced, in all quarters 

 where dry land appears, the same phenomena. 



In the preceding pages we have spoken of the elevation of land 

 from the sea as a thing perfectly well understood, and admitted as a 

 basis of reasoning. It is so admitted by geologists of every shade of 

 opinion who wish to explain effects by real causes. We shall here 

 present a short sketch of the reasons which have produced on this 

 important point so general an agreement among geologists. 



1. In existing nature the combined influence of the exterior and 

 interior causes of change cannot materially affect the level of the sea 

 (as estimated by the mean radius of its surface). Within sensible 

 limits the sea-level is now permanent. 2. The land now above the 

 waters was formerly below them, and could only have been laid bare 

 by the elevation of parts of the sea-bed, or by the abstraction of the 

 ocean to other regions, either through depression of its bed or through 

 a displacement of the axis of rotation, or by an universal diminution 

 of the quantity of water on the globe, or by a change of the oceanic 

 level through great alterations of temperature at the surface or through 

 the mass of the globe. 



In examining these possible modes of desiccation of land, geology 

 must have recourse to collateral science. The two last hypotheses, 

 namely, of a change of oceanic level, without change of external 

 form or axis of rotation, are insufficient for the purpose. Sound 

 reasoning rejects the supposition of an indefinite waste of oceanic 

 waters for miles in depth, because the position of our planet in space 

 yields no escape for the water; nor is there any ground for believing 

 that the quantity fixed in mineral compounds since the date of the 

 earliest strata is of much importance. A general change of tempe- 

 rature of the globe would certainly alter the relative level of land 

 and water, because their rates of expansion and contraction are 

 unequal. Between the boiling heat, 21 '2% and what is probably below 

 the mean temperature of the actual seas, 40, the contraction of the 

 water would be about '042 of the whole quantity. The land certainly 

 would contract less, and thus by a general cooling of the globe the 

 ocean-level would relatively sink. To put the case to extreme, we 

 shall suppose the contraction of the land = 0, the area of the water 

 to remain unchanged, and the mean depth of the sea ten miles ; the 

 reduction of level of the ocean would be -j- 4 ^ of a mile = 739 yards. 

 Now, as all the conditions of the problem have been taken in extreme, 

 as the deepest part of the sea probably does not exceed ten miles, as 

 one quarter of the spherical surface is land, and the area of the sea 

 must diminish as its level sinks, it is very obvious that the greatest 

 possible change of oceanic level from this cause could only go to one, 

 two, or three hundred yards at most ; and therefore it is impossible 

 by such means to explain the desiccation of laud from 1000 to 10,000 

 or 20,000 feet high. 



Moreover, during this cooling of the land and sea the whole globe 

 would contract; and from this cause the mean radius of the ocean 

 diminish and its mean depth augment, so as to reduce still more the 

 possible extent of laud that could be drained by its change of 

 dimensions. 



The attraction of the ocean to other regions would lay dry parts of 

 its bed ; and if astronomical science -permitted geologists to change 



