LIBRARY 
 
 UNIVERSITY OF 
 ^CALIFORNIA/ 
 
 EARTH 
 
 SCIENCES 
 
 LIBRARY 
 
^GEOLOGICAL MAP OF 
 
 (iKKAT BRITAIN 
 
THE 
 
 PHYSICAL GEOLOGY AND GEOGEAPHY 
 
 OP 
 
 GEEAT BRITAIN. 
 
 SIX LECTUEES 
 
 TO WORKING MEN 
 
 DELIVERED IN THE ROYAL SCHOOL OF MINES 
 IN 1863. 
 
 BY A. 0. EAMSAY, F.E.S. 
 
 LOCAL DIRECTOB OF THE GEOLOGICAL SURVEY OF GREAT BRITAIN. 
 
 SECOND EDITION. 
 
 LONDON: 
 
 EDWARD STANFORD, 6 CHARING CROSS. 
 1864 
 
There rolls the deep where grew the tree. 
 
 earth, what changes hast thou seen! 
 
 There where the long street roars, hath been 
 The stillness of the central sea. 
 
 The hills are shadows, and they flow 
 
 From form to form, and nothing stands ; 
 They melt like mist, the solid lands, 
 
 Like clouds they shape themselves and go. 
 
 TENNYSON. 
 
 LONDON 
 
 PBTNTED BY SPOTTISWOODE AND CO. 
 NEW-STBEET SQUABE 
 
EARTH 
 SCIENCES 
 LIBRARY 
 TO 
 
 THE MEMOKY 
 
 OF 
 
 SIE HENRY THOMAS DE LA BECHE 
 
 C.B., F.E.S. 
 
 TO WHOSE EAELY TEACHINGS IN 
 
 PHYSICAL GEOLOGY 
 I AM SO MUCH INDEBTED, 
 
 THIS LITTLE BOOK 
 
 IS 
 AFFECTIONATELY DEDICATED 
 
PEEFACE. 
 
 HIKE first edition of these Lectures was printed from 
 * the shorthand report of Mr. I. Aldous Mays, and 
 published with my consent. At his request I read and 
 corrected the proof-sheets ; but being much occupied at 
 the time with other necessary work, and not in perfect 
 health, many imperfections and mistakes, and a few 
 positive errors, escaped my notice. In this edition 
 the whole has been thoroughly revised, corrected, and 
 in parts almost rewritten, and a good deal of fresh 
 matter has been added, including a map, reduced for 
 England from my own geological map, and for Scot- 
 land from the map by Sir Koderick Murchison and 
 Mr. Greikie. 
 
 My object in delivering the original course, and in 
 publishing this edition, has been to show how simple 
 the geological structure of Great Britain is in its 
 larger features, and how easily that structure may be 
 
VI PREFACE. 
 
 explained to, and understood by, persons who are not 
 practised geologists. Any one with a very moderate 
 exertion of thought may thus realise the geological 
 meaning of the physical geography of our country, 
 and, almost without effort, add a new pleasure to those 
 possessed before as he travels to and fro. The colours 
 on geological maps will then no longer appear mys- 
 terious, but become easy to comprehend when associated 
 with the geography of our island ; and the little book 
 may thus serve as a kind of condensed explanation of 
 geological maps of Great Britain, and perhaps smooth 
 the way for those who are just entering on the subject 
 and feel alarm at its seeming difficulties. 
 
 ANDREW C. EAMSAT. 
 
 3 
 
 KENSINGTON: January 1864. 
 
CONTENTS. 
 
 LECTURE I. 
 THE CLASSIFICATION OF EOCKS. DENUDATION . 
 
 LECTUEE II. 
 THE PHYSICAL STRUCTURE OF SCOTLAND 27 
 
 LECTUEE HI. 
 THE PHYSICAL STRUCTURE OF ENGLAND 64 
 
 LECTUEE IV. 
 
 THE MIOCENE AND PLIOCENE TERTIARY STRATA. GLACIAL PHENO- 
 MENA; AND ORIGIN OF CERTAIN LAKES .... 90 
 
 LECTUEE V. 
 
 NEWER PLIOCENE EPOCH, CONTINUED. BONE-CAVES. DENUDATION 
 OF THE COASTS OF BRITAIN. BRITISH CLIMATES AND THEIR 
 CAUSES ; AREAS OF DRAINAGE, EIVER VALLEYS, AND THEIB 
 ORIGIN; OLD EIYER GRAVELS, AND PRE-HISTORIC HUMAN 
 EEMALXS. HISTORICAL ELEVATION OF THE COUNTRY . .124 
 
 LECTUEE VI. 
 
 QUALITIES OF WATERS. CONNECTION OF THE PHYSICAL GEOLOGY 
 
 OF THE COUNTRY WITH THE POPULATION . . . .157 
 
LECTUEE I. 
 
 THE CLASSIFICATION OF KOCKS. DENUDATION. 
 
 IN the good old days, those who thought upon the 
 matter at all were perfectly content to accept the world 
 as it is, believing that from its beginning to the 
 present day it had always been much as we now find it, 
 and that till the end of all things shall arrive, it will, 
 with but slight modifications, always remain the same. 
 But, by and by, when geology began to arrive at the 
 dignity of a science, it was found that the world had 
 passed through many changes ; that the time was when 
 the present mountains and plains were not, for the 
 strata of which both are formed were once themselves 
 sediments derived from the waste of yet older ranges. 
 Thus it happens that that which is now land has often 
 been sea, and frequently what is now sea has been 
 land; and so there was a time before the existing 
 rivers began to flow, and when all the lakes of the 
 world, as we now know them, had no place on the 
 earth. The whole subject is of the greatest interest, 
 
 B 
 
2 Classification of Rocks : 
 
 and it is therefore my intention, in this course, to 
 endeavour to show you taking our own island as an 
 example the reason why one part of a country consists 
 of rugged mountains, and another part of low plains, or 
 of high table-lands ; why the rivers run in their present 
 channels, and how the lakes that diversify the surface 
 first came into being. 
 
 Experience tells me that at these courses of lectures 
 a number of my old friends come to see me again and 
 again, and also that there are many new faces present. 
 Nevertheless, because so many of the old come to hear 
 them, it is an object with me to vary the subjects as 
 much as possible, so as to convey in each course some 
 kind of instruction that was not given before. But as 
 by the necessities of my position, and of my particular 
 kind of knowledge, I am obliged to confine myself to 
 subjects either purely geological, or intimately con- 
 nected with geology, it is needful for the benefit of 
 those who have not heard any of the previous lectures, 
 that at the beginning I should enter on some of the 
 rudimentary points of the subject, so as to make the 
 remainder of the course intelligible to all. Therefore I 
 "begin to-night with an account of the origin of rocks ; 
 because it is impossible to understand the origin of the 
 various kinds of scenery of our country, and to account 
 for the classification of its mountains and plains without 
 explaining the nature of the rocks which compose them. 
 
Aqueous and Igneous. 3 
 
 Without further preface, then, all rocks are divided 
 into two great classes AQUEOUS and IGNEOUS and 
 there is a sub-class, which consists of aqueous rocks 
 that have been altered, and which in their characters 
 often approach some of those rocks that have been 
 termed Igneous, in a popular sense, though in many 
 respects very different from volcanic products. In this 
 lecture I shall, however, confine myself to a general 
 description of the two great classes of rocks ; those of 
 aqueous or watery origin, and those of igneous origin, 
 which are the product of heat. 
 
 By far the larger proportion of the rocks of the 
 world were formed by the agency of water. But, by 
 what special processes were they formed ? Every one 
 knows that the rain which falls upon the land, draining 
 the surface, first forms brooks, and that these brooks 
 running into common channels and joining, by degrees 
 become rivers ; and every one who has looked at large 
 rivers knows that they are rarely pure and clear, 
 notably, for instance, in the case of the Thames. Every 
 river, in fact, carries sediment and impurities of various 
 kinds in suspension or held in solution, and this mat- 
 ter, having been derived from the waste of the lands 
 through which rivers flow, is carried to lower levels. 
 Thus it happens that when rivers empty themselves 
 into lakes, or what is far more frequently the case 
 into the sea, the sediments that they hold in solution 
 
 B2 
 
4 Classification of Rocks. 
 
 are deposited at the bottom of the lakes, or of the sea, 
 as the case may be, and constantly increasing, they 
 gradually form accumulations of more or less thick- 
 ness, generally arranged in beds, or, as geologists usually 
 term them, in strata. Thus, for instance, suppose any 
 given river flowing into the sea. It carries sediment in 
 suspension, and a layer will fall over a part of the sea- 
 bottom, the coarser and heavier particles near the 
 shore, while the finer and lighter matter will be carried 
 out by the current and deposited further off. Then 
 another layer of sediment may be deposited on the top 
 of it, and another, and another, until, in the course of 
 time, a vast accumulation of strata may in this manner 
 be formed. 
 
 Again, if we examine the sea-coast where cliffs rise 
 from the shore, we find that the disintegrating effect of 
 the weather, and of the waves beating upon the cliffs 
 gradually wears them away, comparatively quickly when 
 made of clay or other soft strata, and in other cases 
 very slowly perhaps, but still sensibly to the observant 
 eye, so that in time, be they ever so hard, they get 
 worn more and more backwards. The material derived 
 from this waste when the cliffs are truly rocky, in the 
 first instance, generally forms shingle at their base, as, 
 for instance, with the pebbles of flint formed by the 
 waste of the chalk. These being acted upon by the 
 waves, are rolled incessantly backwards and forwards, 
 
Stratified Rocks. 5 
 
 as every one who has walked much by the sea must 
 have noticed ; for when a large wave breaks upon the 
 shore, it carries forward the shingle, rolling the frag- 
 ments one over the other, and in the same way they 
 recede with the retreating wave with a rattling sound. 
 This continued action has the effect of grinding angular 
 fragments into rounded pebbles ; and, in the course of 
 time, large amounts of loose shingle are often thus 
 formed. Such material when consolidated forms con- 
 glomerate. If, also, we examine with a lens the 
 fragments that compose such a rock as sandstone, 
 we shall find that it is formed of innumerable grains of 
 quartz, and that these grains are often not angular but 
 more or less rounded ; and if you take up a handful of 
 sea-sand and examine it in the same manner, you will 
 frequently find that it does not consist of a quantity of 
 small angular fragments, but of grains, the edges of 
 which have been worn off by the action of the waves 
 moving them constantly backwards and forwards upon 
 themselves.' Thus the little particles rubbing for ages 
 upon each other, their angularity is gradually worn off, 
 and they become grains, like rounded pebbles in shape, 
 only much smaller. In this manner a very large 
 amount of mechanical sediments are forming and have 
 been formed. 
 
 If we examine the rocks that form the land, we very 
 soon discover that a large proportion of them are 
 
6 Classification of Rocks. 
 
 arranged in layers or bands of shale, sandstone, or 
 conglomerate, in a manner analogous to that which I 
 have just described as taking place at the mouths of 
 rivers and in the sea, thus proving that these layers 
 have been formed by the action of water. Take, for 
 instance, a possible cliff b;y the sea-shore, and we shall 
 probably find that it is made of a number of strata, 
 which may be horizontal, as in fig. 1, or inclined, or 
 even bent and contorted into every conceivable variety 
 of form, as in parts of figs. 3 and 4. If, as in the fol- 
 lowing diagram, we take a particular bed, No. 4, we 
 
 Kg. 1. 
 
 may find that it consists of sandstone, formed of a 
 number of differently-coloured layers arranged one 
 upon the top of another. Bed No. 3 may be of coarser 
 pebbly material, also arranged in layers, but not so 
 regularly as in No. 4, because the material is coarser. 
 No. 2 may consist of beds of thin shale of the finest 
 material, also arranged in layers, but the material being 
 much finer, each individual layer may be as thin as a 
 sheet of paper. Then in No. 1, the next and lowest 
 deposit, we may have a mass of limestone, arranged in 
 massive beds, the whole in the aggregate forming one 
 
Fossils. 7 
 
 cliff. Kocks, more or less of these kinds, compose the 
 bulk of the British islands ; and remember that these 
 were originally loose stratified sediments, piled on each 
 other often to enormous thicknesses, and consolidated 
 and hardened by pressure and chemical action. In 
 some cases they have since been still further altered by 
 heat and other agencies, but sometimes they are almost 
 undisturbed except by mere upheaval, while in other 
 cases the beds have been violently broken and con- 
 torted. 
 
 Then comes the question : Under what special con- 
 ditions were given areas of these rocks formed? When 
 we examine them in detail, we generally find that most 
 of them contain, more or less, fossils of various kinds, 
 shells, corals, sea-urchins, the remains of plants and 
 fishes, &c., and more rarely of the bones of terrestrial 
 animals. For instance, in the bed of sandstone, No. 4 
 (fig. 1), we might find that there are remains of sea- 
 shells; occasionally but more rarely similar bodies 
 might occur in the conglomerate, No. 3 ; frequently 
 they might lie between the thin layers of shale in 
 No. 2 ; and it is equally common to find large quantities 
 of shells, corals, sea-urchins, encrinites, and various 
 other forms of life in such limestones as No. 1, which, 
 in a number of cases, are wholly, or very nearly, com- 
 posed of entire or broken shells and other marine 
 organic remains. 
 
8 Classification of Rocks. 
 
 Now, though strata of limestone have, in great part, 
 been mechanically arranged, yet it comparatively rarely 
 happens that quantities of unmixed calcareous sediment 
 have been- carried in a tangible form by rivers to the 
 sea, or yet that it has been directly derived from the 
 waste of sea-cliffs. When, therefore, it so happens 
 that we get .a mass of marine limestone consisting 
 entirely of shells, which are the skeletons of marine 
 creatures, the conclusion is forced upon us that, be the 
 limestone ever so thick, it has been formed entirely by 
 the growth and death of marine animals. In many a 
 specimen, for instance from beds called the Carboni- 
 ferous limestone, the naked eye tells us that it is 
 formed perhaps entirely of rings of Encrinites, or stone- 
 lilies as they are termed ; and in many other cases 
 where the limestone is homogeneous, the microscope 
 reveals that it is made of exceedingly small particles 
 of organic remains. It sometimes happens that such 
 beds of limestone attain the enormous thickness of five 
 hundred feet, or even of from one to four thousand 
 feet in vertical thickness. 
 
 I will not tell you at present how we attain to the 
 knowledge of the enormous thickness of these strata, 
 because it would lead to a geological discussion which 
 is, to a great extent, foreign to my present object; so 
 that I must ask you to believe and take for granted, 
 that the fact is so. But where does all the lime come 
 
Limestone, how formed. 9 
 
 from by which these animals make their skeletons ? If 
 you analyse the waters of the rivers that run through 
 our own valleys, you will discover that most of them 
 consist of hard water that is to say, it is not pure 
 like rain-water, but contains a quantity of various 
 kinds of salts in a state of chemical solution, the 
 most important of which is generally lime; for the 
 rain-water that falls upon the surface of the land per- 
 colates the rocks, and rising again in springs, carries 
 with it, if the rocks be at all calcareous, a quantity of 
 lime in solution. The reason of this is, that all rain 
 in descending through the air takes up a certain 
 amount of carbonic acid one of the constituents, acci- 
 dental or otherwise of the air; and this carbonic 
 acid has the power of dissolving the lime which, more 
 or less, enters into the composition of a large pro- 
 portion of stratified rocks. In this way it happens 
 that springs are often charged with lime, in the form 
 of what chemists call a soluble bi-carbonate, which is 
 carried into the rivers, and finding its way to the sea 
 affords material to shell-fish and other marine animals, 
 through their nutriment to make shells, bones, and 
 tissues ; and thus it happens, that by little and little 
 lime is abstracted from the sea-water to form parts 
 of animals, which dying, frequently produce, by their 
 skeletons or shells, immense strata of nearly pure 
 limestone. 
 
io Classification of Rocks. 
 
 But it often happens that along with shells there 
 are various other sediments found in the form of mud 
 or sand carried from the land into the sea ; and in 
 this case, instead of pure limestone being formed, you 
 get impure limestone, or mixtures of shells with 
 common mud, sand, or pebbles, as the case may be. 
 In one case, for instance, we have a mass of rock 
 formed of consolidated mud, and the shells of oysters ; 
 and by reason of the oyster-shells we obtain a large 
 percentage of lime in this specimen. In like manner 
 many other varieties of material may be intermingled, 
 as it were, almost at random. Sometimes strata consist 
 of lime and sand, or of lime, sand, and pebbles, or of 
 any two or all of these, mixed or alternating till they 
 become tens, or hundreds, or thousands of feet thick ; 
 but when the limestone is pure and formed of organic 
 remains, its formation must have taken place in a sea, 
 or more rarely in fresh water, in which other sediments 
 at that time and in that locality were not being formed. 
 
 The other class of rocks, to which I have alluded, 
 are termed Igneous, and form a much smaller proportion 
 of the outer rocks of the entire world. Thus, to take 
 England and Wales as an example : in North Wales, in 
 Merionethshire, Carnarvonshire, and Anglesea, a con- 
 siderable proportion, perhaps a tenth part, of the rocks 
 are formed of igneous masses. The whole of the rest 
 of Wales, down to Pembrokeshire, contains almost none 
 
Igneous Rocks. 1 1 
 
 whatever. But for twenty miles eastward of SU 
 David's Head, we have igneous rocks more or less dis- 
 tributed. The same comparatively small proportion of 
 igneous rocks is found in parts of Scotland and Cum- 
 berland, and they also exist in Derbyshire, Devon, and 
 Cornwall ; whereas, if we examine all the midland, 
 southern, and eastern parts of England, we shall find 
 no igneous rocks whatever. 
 
 Now I have to explain how we are able to distin- 
 guish igneous from aqueous rocks ; and, in a general 
 way, I would say, that we can do so because most of 
 them are unstratified, and have other external and 
 internal structures different from those of aqueous 
 deposits. To take examples : If we examine the 
 rocks from any existing volcano, we find that the lavas 
 poured out by it are frequently vesicular. This vesi- 
 cular structure is due to gases and watery vapour 
 in the melted mass, and these expanding, in their 
 efforts to escape, blow out the melted rock and form a 
 number of slnall vesicles or bubbles, just as yeast 
 does in bread, and this peculiar vesicular structure is 
 never found in the case of stratified rocks. Here then 
 experience tells that any rock with this structure once 
 formed part of a melted mass. I may know another 
 specimen, which is crystalline, to be part of an old 
 lava stream, because some one who obtained it, and on 
 whose word I rely, told me that such was the fact, or 
 
12 Classification of Rocks. 
 
 I have seen such cases, and know that this structure 
 is characteristic of some volcanic rocks, arising from 
 the circumstance that, in cooling, the substances of 
 which the lava is composed crystallised in distinct 
 minerals according to their chemical affinities. Another 
 specimen may be from a rock which no man ever saw in 
 a melted state ; because it was fused, and cooled, and 
 consolidated long before any human being looked upon 
 creation. It belongs to a period called in Geology that 
 of the Coal-measures ; and when I examine its structure 
 I find that it is nearly the same as in a specimen pre- 
 viously alluded to. It has been- vesicular, but is not 
 so any longer, because it happens that the original 
 vesicles have been filled by infiltration of carbonate 
 of lime. The mass has in fact been long under ground, 
 and was infiltrated by water that, percolating through 
 limestone rocks, carried lime in solution into the once 
 empty vesicles. In these empty vesicles it has been 
 deposited as carbonate of lime. But it frequently 
 happens that the carbonate of lime, after such a rock 
 has been exposed on the surface, is dissolved out by 
 the carbonic acid held in rain-water, which again carries 
 it away in solution as a bi-carbonate of lime, and then 
 such a specimen again assumes a vesicular character 
 analogous to that of some modern lavas. Therefore I 
 should presume that this was an igneous rock. Again, 
 we find that igneous rocks, in cooling, become crystal- 
 
Igneous Rocks. 13 
 
 line although they do not all do so. The melted 
 mass, in the first . instance, consists of a number of 
 substances mingled together ; but as it cools, these 
 substances, under certain conditions, are apt to ar- 
 range themselves according to their chemical affinities, 
 and the result is the development of various minerals 
 in the rock as, for instance, feldspar and augite. 
 On cooling, the constituents re-arranged themselves; 
 like drew to like, and the result was crystals of 
 feldspar, and crystals of augite. When I go abroad 
 and examine other igneous rocks, where no volcanic 
 action has occurred in the memory of man, or even for 
 an incalculable number of years before his existence, I 
 find, as in the case of the specimen from the Coal-mea- 
 sures, a structure similar, to that which I observe in 
 certain modern lavas, and infer their igneous origin. 
 
 Again, if I take a specimen of another lava from 
 a volcano not long extinct in the Island of Ascension I 
 find that it is arranged in layers which in some degree 
 bear a resemblance to those which I have described as 
 layers of stratification ; but if I compare it with the 
 slag which flows from iron furnaces, I find that they 
 are still more like that. Slag is in fact nothing but 
 artificial lava, being part of the silica and alumina of 
 the original iron ore and its flux of lime melted up 
 together. It frequently assumes a ribbon-like structure, 
 as any one must have observed, who has noticed slag as 
 
14 Classification of Rocks. 
 
 it flows out of the furnace in a number of different 
 coloured bands, and this old lava from the Island of 
 Ascension presents the same wavy ribbon-like appear- 
 ance. When I go to Wales and examine in the Silurian 
 region some of the oldest known lavas in the world, 
 I discover a similar structure an arrangement in 
 slaggy-like layers ; and therefore I infer that they were 
 ancient streams of lava. 
 
 Now, what would be the effect of a melted mass 
 of igneous rock coming in contact with stratified rocks, 
 such as some of these upon the table ? The effect 
 would naturally be that, if the heat were sufficiently 
 strong, and if it were long enough applied, the stra- 
 tified rock at the point of contact would undergo some 
 kind of alteration. If you place a mass of sandstone in 
 an iron furnace or, better still, if you examine the 
 sandstone floor of an iron furnace where a perpetual 
 heat has been kept up for a long series of years 
 where in fact the floor of the furnace has been in 
 contact with substances which are more or less of the 
 nature of melted lavas ; this floor is found to be 
 changed. The sandstone is no longer comparatively 
 soft, as it was in its original state, but it has been 
 metamorphosed, or baked, and turned into a substance 
 which is known to geologists as ( quartz-rock ; ' the 
 colour is discharged, it has become white and hard, and 
 breaks with a splintery fracture. If again we submit 
 
Altered Rocks. 1 5 
 
 rocks composed originally of clay, like shales or slates, 
 to intense heat, they assume the appearance of a kind 
 of porcelain, and so completely is this recognised by 
 geologists, that the term applied to rocks thus altered, 
 is that it has been ' porcelainised,' or baked like 
 potter's clay. 
 
 When I come to places among the hills where igneous 
 or trap rocks rise through layers of sandstones, perhaps 
 in a vertical manner, or where they send out branches 
 hither and thither in among the beds, if I examine the 
 strata at the point of contact with these, I find that 
 the stratified rock has often altered its texture and 
 structure, and changed its colour : and as you recede 
 from the point of contact, it gradually becomes softer 
 and softer until it parses into ordinary shale or sand- 
 stone. Experience has shown me that this is the effect 
 of artificial heat, and also by actual observation I know 
 that it has taken place in volcanic countries ; and once 
 having arrived at this point of experience, I have very 
 little difficulty in other cases in determining whether 
 or not I am in the presence of an igneous or a stratified 
 rock, altered or unaltered as the case may be. And 
 thus is it that geologists, by a process of analysis, are 
 enabled to determine that the whole rock-masses of 
 the outer world consists of two great classes one class 
 being Igneous and the other Aqueous. 
 
 The next point to be considered is Are rocks of 
 
1 6 Classification of Rocks. 
 
 different ages ? This they evidently are, and the 
 diagram, fig. 1, will assist us to make it clear. There 
 the bed No. 1 must be the oldest, and the next, 
 No. 2, a little younger, because it was deposited upon 
 one already formed, and which therefore lies below, 
 and so on to 3 and 4 taking the strata in different 
 stages. But that is not enough to know. We are 
 anxious to understand what is the actual history of the 
 different stages which these rocks represent. Now, if 
 we had never found any fossil remains, we should lose 
 half the interest of this investigation, and our discovery, 
 that the rocks were of different ages, would have only 
 a minor value. Let us turn again to the diagram. We 
 find at the base a bed- No. 1, say of limestone, com- 
 posed of shells, the shells in the upper part of the bed 
 lie above those in the lower part, and therefore these 
 shells, or any other organic remains you please, in the 
 lower part of the bed, were dead and buried before 
 the once living shells which lie in the upper part came 
 into the area. Above the bed of shale, No. 2, there is 
 another stratum, No. 3, a conglomerate, and then comes 
 the bed of sandstone, No. 4 ; therefore the shells in the 
 bed of shale, No. 2, are of younger date than those in 
 the bed of limestone, No. 1 ; the shells in the conglo- 
 merate, No. 3, are newer than those in the shale, and 
 those in the sandstone, No. 4, are latest of all; and 
 each of these particular forms had lived and passed 
 
Superposition of Formations. 17 
 
 away in succession before the sediment began to be 
 formed in the bed above. All these beds, therefore, 
 contain relics of ancient life of different dates, each 
 bed being younger or older than the others according 
 to the manner in which we read them. 
 
 But if we leave a petty cliff and examine the rocks 
 on a larger scale, what do we find ? Let us take, for 
 instance, the middle of England from the borders of 
 South Staffordshire and Warwickshire to the neigh- 
 bourhood of London ; then we discover that the whole 
 series is made of strata, formed more or less in the 
 manner which I have described, in successive stages, 
 the middle and upper parts of which added together 
 are represented in the table at page 20, and in colours 
 on the map. Thus, through Warwickshire and South 
 Staffordshire, we have rocks formed of New red sand- 
 stone ; the red sandstone dips to the east, and is over- 
 laid by New red marl ; the red marl dips also to the 
 east, under beds of blue clay, limestone, and brown marl, 
 called the Lias ; these pass under a great succession of 
 formations of limestones, clays, and sands, &c., which 
 geologists have termed Oolites ; these, in their turn, are 
 overlaid by beds of sand, clay, and chalk, named the 
 6 Cretaceous strata ; ' which again, in their turn, pass 
 under the Tertiary clays and sands of the London 
 Basin. All these pass fairly under each other in the 
 
 c 
 
1 8 Classification of Rocks. 
 
 order thus enumerated. Experience has proved this, 
 for though there are occasional interruptions, some of 
 the formations being absent in places, yet the order of 
 succession is never inverted, except where, by what may 
 be called geological accidents, in some parts of the 
 world great disturbances have locally produced forcible 
 inversions of some of the strata. The Oolites, for 
 example, when little disturbed, never lie under the 
 Lias, nor the Cretaceous rocks under the Oolites. 
 
 It is, therefore, not merely that the mere surface of 
 the land is formed of various rocks, but the several 
 formations dip or pass under each other in regular 
 succession, being, in fact, vast beds placed much in 
 the same way as a set of books, placed flat on each 
 other, and then slightly tilted up at one end, may 
 slope in one direction. As further proof of this suc- 
 cession, I may refer to the London basin, where we 
 have strata round London, called the London Clay. 
 Well sinkers frequently bore several hundreds of feet 
 through this, and invariably they come to the chalk 
 beneath ; and so, if in some other places we bored 
 through the chalk, we should come to Oolites, and if 
 we bored through the Upper Oolites, we should come 
 to the Middle and Lower Oolites, and so on through 
 the Lias and other strata ; and if we go further west, 
 we find older more disturbed formations, cropping 
 
Succession of Species. 19 
 
 out in succession to the surface. Vertical sinking 
 therefore often proves practically, what we know theo- 
 retically, viz. the underground continuity of strata one 
 beneath the other, so that our island is formed of a 
 series of beds of rock, some of many hundreds and 
 some of several thousands of feet in thickness, arranged 
 in succession, the lowest formation being of oldest and 
 the uppermost of youngest date. 
 
 As we proceed from west to east, and examine 
 minutely the various kinds of fossils found in those 
 successive formations, we soon discover that they are 
 not the same in all, and that most of them contain 
 marine organic remains, which are in each formation 
 of genera and species more or less distinct from those 
 in the formation immediately above or immediately 
 below. There are also a few freshwater deposits, and 
 all of the fossil-bearing formations, whether of fresh- 
 water or of marine origin, contain the remains of 
 animals that lived and died in the waters of the re- 
 spective periods. 
 
 After a minute examination, therefore, of the struc- 
 ture of our island, the result is that geologists are able 
 to recognise and place all the rocks in serial order, so 
 as to show which were formed first and which were 
 formed latest, and the following is the result of this 
 tabulation, omitting minor details. 
 
 C 2 
 
Classification of Rocks. 
 
 TABLE OF THE BRITISH FORMATIONS. 
 
 Recent. 
 
 l! 
 
 |1 
 
 H 
 
 MIDDLE. 
 
 Post Pliocene. 
 
 J River gravels, raised 
 \ beaches, bone caves, &c. 
 
 Hempstead beds. 
 Various formations, 
 chiefly freshwater. 
 
 
 CRETACEOUS. 
 
 
 WEALDEN 
 
 SERIES. 
 
 'o 
 
 f 
 
 g< 
 
 OOLITIC 
 
 SERIES, 
 
 f 
 
 
 1 
 
 and 
 LIAS. 
 
 
 TRIASSIC. 
 
 
 PERMIAN, 
 
 CARBONIFE- 
 ROUS. 
 OLD RED 
 
 .g , SANDSTONE, & 
 DEVONIAN. 
 
 SILURIAN. 
 
 CAMBRIAN. 
 LAWRENTIAN. 
 
 L Older Pliocene. 
 Miocene. 
 
 r Upper Eocene. 
 
 j Middle Eocene. 
 I Lower Eocene. 
 
 Chalk. 
 
 Upper Greensand. 
 
 Gault. 
 
 Lower Greensand. 
 
 Wealden. 
 
 Purbeck Beds, 
 f Portland Oolite. 
 
 Kimeridge Clay. 
 
 Coral Rag. 
 
 Oxford Clay. 
 
 Cornbrash. 
 
 Forest Marble. 
 
 Bath Oolite. 
 
 Stonesfield Slate. 
 
 Inferior Oolite. 
 
 Upper Lias Clay and sand. 
 
 Marlstone (Middle Lias). 
 
 Lower Lias Clay and Limestone. 
 
 Upper. New red marl (Keuper). 
 
 Lower. New red sandstone (Bunter). 
 f Magnesian limestone. 
 
 Permian. ( Rofhliegende. 
 
 r Coal-measures. 
 j Carboniferous limestone and shales. 
 
 } 
 
 Upper Silurian. 
 Lower Silurian. 
 
The Formations. 21 
 
 The Lawrentian rocks, which are the oldest known 
 formation in the world, lie in Scotland in some of 
 the Western Isles and the western parts of Sutherland, 
 and consist of gneiss in a very far advanced stage of 
 metamorphism. 
 
 The Cambrian rocks, which succeed them, contain a 
 few obscure fossils, and the area occupied by this series 
 is not large, being chiefly confined to small parts of 
 Shropshire and Wales and the north-western part of 
 Scotland. If we examine the Silurian rocks, which 
 come next in succession, and which occupy for the most 
 part Wales and Cumberland, we there find the relics 
 of a number of peculiar forms of life, which, in the 
 lower and upper divisions of the series, are vastly 
 developed, both numerically and specifically; so with 
 the succeeding age, the Devonian; so with the Car- 
 boniferous and Permian epochs ; then through the Trias 
 and Lias to the Oolitic epochs and their fossils ; then, 
 still higher in the scale of time, we arrive at the 
 Cretaceous series, and so on into the Eocene beds and 
 higher Tertiary strata, till at last we corne to the pre- 
 sent age. It is not, however, my business, in lectures 
 bearing specially on physical geography, to give you 
 a description of the various organic forms that have 
 lived through these ages : that can only be done in a 
 regular course of palseontological lectures. 
 
 Thus by an analysis of the order of deposition of the 
 
22 Classification of Rocks. 
 
 rocks and their contents, geologists led by the re- 
 searches of the father of modern geology, William 
 Smith are enabled to come to the important conclu- 
 sion, that each formation was marked by its own 
 peculiar forms of life; that is to say, that each 
 formation was in its time a sea-bottom or a series of 
 sea-bottoms, in which peculiar kinds of life nourished, 
 which life for some reason in part or altogether disap- 
 peared, before a new period commenced, in which new 
 species inhabited the waters, which in their turn also 
 slowly died out ; and so on in successive stages, from the 
 oldest epochs, through the whole of the formations, until 
 at last we come to the epoch in which we are now living. 
 
 It was necessary to explain this, because I shall have 
 frequent occasion to speak of the rocks by their names, 
 and to show their physical relations to each other in a 
 scenic point of view, these relations being connected 
 with phenomena dependent on their ages. 
 
 But before starting on this new subject, I must ex- 
 plain the meaning of a term which I shall have occa- 
 sion to use ver} T frequently, namely, Denudation. 
 
 4 Denudation,' in the geological sense of the word, 
 means the stripping away of rocks from the surface, 
 so as to expose other rocks that lie beneath them. 
 
 Water running over the surface wears away the 
 ground over which it passes, and carries away detrital 
 matter, such as pebbles, sand, and mud, and if this goes 
 
Denudation. 23 
 
 on long enough over large areas, there is no reason why 
 any amount of matter should not in time be removed. 
 For instance, we have a notable case in North America 
 of a very considerable result from denudation, now 
 being effected by the river Niagara, where, below the 
 Falls, the river has cut a deep channel through the rocks, 
 about seven miles in length. The proofs are perfect 
 that the Falls originally began at the great escarpment 
 which is at the lower end of what is now this long 
 gorge ; that the river, falling over this ancient cliff, by 
 degrees wore for itself a channel backwards, about a 
 hundred and sixty feet deep, through strata that on 
 either side of the gorge form a great plateau. 
 
 I merely give this instance to show you what I mean 
 by denudation produced by running water. At one 
 time the channel did not exist. The river has cut it 
 
 out, and in doing so, strata formerly one hundred and 
 
 i 
 
 sixty feet beneath the surface have been exposed by 
 denudation. Probable but very uncertain calculations 
 show that to form this gorge a period at the least of 
 something like ten or twelve thousand years has been 
 
 employed. 
 
 Fig. 2. 
 
 Now, refer to fig. 2, and suppose that we have 
 different strata, 1, 2, 3, and 4, lying horizontally one 
 
24 Denudation 
 
 above the other, together forming a mass several hun- 
 dreds of feet in thickness. Kunning water in the state 
 of a brook or river by degrees wears away the rocks 
 more in one place than another, so that the formations 
 or strata 3, 2, and 1 are successively cut into and exposed 
 at the surface, and a valley may in time be formed. 
 This is the result of denudation. 
 
 In another way rain-water charged with carbonic 
 acid, falling age after age on limestone rocks such as the 
 chalk, not only wears away part of these rocks by ordi- 
 nary denudation, but also dissolves the lime and carries 
 it. off in solution, thus by waste of the upper beds 
 bringing the lower strata to the surface. The evidence 
 of the former existence of the wasted beds of chalk is 
 witnessed, by prodigious numbers of unworn flints, 
 scattered on the surface, these insoluble flints having 
 once formed interrupted beds well apart from each 
 other in the mass of the denuded chalk. 
 
 The constant atmospheric disintegration of cliffs, and 
 the beating of the waves on the shore, is also another 
 
 mode by which watery action denudes and cuts back 
 
 i 
 rocks. Caverns, bays, and other indentations of the 
 
 coast, needle-shaped rocks standing out in the sea 
 from the main mass of the cliff, are all caused by 
 the long-continued wasting power of the sea, which 
 first helps to destroy the land and then spreads the 
 ruins in new strata over its bottom, in time to be 
 
and Reconstruction. 25 
 
 consolidated and again upheaved into land. Denudation 
 by this process has always to a great amount been 
 produced. 
 
 It requires a long process of geological education to 
 enable any one thoroughly to realise the conception of 
 the vast amount of old denudations ; but when we con- 
 sider that, over and over again, strata thousands and 
 thousands of square miles in extent, and thousands of 
 feet in thickness have been formed by the denudation of 
 older rocks, equal in extent to the strata formed by 
 their waste, we begin to get an idea of the greatness of 
 this power. The mind is then more likely to realise 
 the vast amount of matter that in times comparatively 
 quite recent has been swept away from the surface of 
 any country before it has assumed its present form. 
 Without much forestalling the subject of a subsequent 
 lecture, I may now state that a notable example on a 
 grand scale may be seen in the coal-fields of South 
 Wales and of the Forest of Dean. These two coal- 
 fields were once united, but have been separated by the 
 agency of vast and long extended denudations, which 
 have swept away strata thousands of feet thick over a 
 large area of Wales and the adjacent counties. 
 
 Observation and argument alike tell us that we need 
 have no hesitation in applying this reasoning to other 
 areas, and thus we come to the conclusion that the 
 greater portion of the rocky masses of our island have 
 
26 Denudation. 
 
 been arranged and re-arranged, under a slow process of 
 the denudation of old, and the reconstruction of newer 
 strata, extending over periods that seem to our finite 
 minds to stretch into infinity. 
 
 To explain in some detail the anatomical structure of 
 our island, as dependent on the nature of its strata and 
 the alterations and denudations they have undergone, 
 will be the main object of the present course; and if 
 you have been able to follow me in what I have already 
 said, I am sure you will understand what I shall have to 
 say in the remaining lectures. 
 
LECTUEE II. 
 
 THE PHYSICAL STRUCTURE OF SCOTLAND. 
 
 I HAVE now come to that part of the course in which it 
 will be my duty to explain the connection between 
 the geological phenomena of Britain and the nature 
 of its scenery. In this lecture it is my intention to 
 describe that district of Great Britain which is most 
 mountainous, and to explain to you why it is that 
 for the most part Scotland is so rugged. In another 
 lecture I shall have to show you that there is a strong 
 contrast between the physical features of Scotland and 
 that of the middle and eastern parts of England, and 
 to explain why the features o*f these two districts are 
 essentially so distinct. 
 
 In last lecture I commenced by explaining that all 
 rocks are divided into two great classes, namely, those 
 of Aqueous and those of Igneous origin, and I showed 
 you how aqueous rocks may be determined by the 
 circumstance, that a great many of them contain relics 
 
28 Met amor f hie Rocks. 
 
 of marine and other life, in the shape of fossil shells, 
 fish-bones, and various other kinds of organic remains. 
 Also they are what is termed stratified, that is to 
 say, arranged in beds or layers one upon the other, and 
 the materials of which these beds are composed 
 generally show traces of having been acted upon by 
 water ; being rounded and worn by the action of the 
 waves of the sea, or by the running waters of rivers. 
 The other great class of rocks, termed Igneous, are fre- 
 quently crystalline, and from the effects which they 
 produce upon stratified rocks when they are in contact, 
 the latter are often altered. Then by comparing 
 igneous rocks of old date with those of modern volcanic 
 origin, we are able to decide with perfect truth that 
 rocks which were melted long before the human race 
 appeared upon the world, are yet of truly igneous 
 origin ; and all the solid world above the surface of the 
 sea consists of these two great classes of rocks. But 
 there is a third division, which I called a sub-class, 
 known as metamorphic rocks ; that is to say, stratified 
 rocks which have undergone a very serious kind of 
 alteration. All stratified rocks as they assume the solid 
 form become, indeed, to a certain extent altered ; for 
 originally they were loose sediments of mud, sand, 
 gravel, or of lime, spread abroad sometimes in lakes, 
 but chiefly over the sea bottom, for fresh-water beds 
 form but a small part of the strata of the earth. But 
 
Contorted Strata. 
 
 29 
 
 when these were accumulated, bed upon bed, till thou- 
 sands of feet were piled one upon the other, then, by 
 intense and long continued pressure, which alone is 
 sometimes sufficient to harden strata, and by chemical 
 changes which take place in the interior of the strata 
 themselves, by degrees they have become changed into 
 hard masses, consisting of shale, sandstone, conglo- 
 merate, or limestone, as the case may be. But these 
 have not always remained in the same condition in 
 which they were originally consolidated, for it has often 
 happened that disturbances have taken place of a 
 powerful kind, and the originally flat strata have been 
 bent into every possible curve, in some cases for in- 
 stance as shown in the following diagram. 
 
 Fig. 3. 
 
 These are what is termed contorted strata when the 
 disturbance has been extreme. 
 
 Now the metamorphic rocks, about which I have to 
 speak, have been generally highly disturbed, and occupy 
 a very large part of Scotland I may say one-half 
 most of which includes, and lies north-west of the 
 
jo Metamorphic Rocks. 
 
 Grampian mountains ; and I must endeavour to explain 
 by what processes metamorphism of rocks has taken 
 place, not in detail, but simply in such a manner as to 
 give you a general idea of the subject. 
 
 Metamorphic rocks, when the metamorphism is ex- 
 treme, consist of gneiss and mica schist, chlorite schist, 
 crystalline limestone, hornblende rock, and a number 
 of others, which I need not name. It is enough for my 
 present purpose if I make you understand that there 
 are metamorphic rocks. 
 
 A typical specimen of gneiss consists of irregular 
 laminaB of the minerals called mica, quartz, and/eWspar, 
 and it frequently happens that they are bent in a re- 
 markable manner, or rather minutely folded in a great 
 number of convolutions so small, that in a few feet of 
 gneiss they may sometimes be counted by the hun- 
 dred. Long ago all these rocks, that we term meta- 
 morphic, were, by the old geologists, called Primitive 
 strata, and they were considered to have been formed in 
 the earliest stages of the world's history, because in 
 those countries that were first geologically described, 
 they were found or at least were supposed to lie 
 always at the base of the other strata, and from the 
 peculiarity of the minute contortions in the gneissic 
 rocks a theory now known to be erroneous was de- 
 veloped, which was this : 
 
 It is frequently found that granite and granitic rocks 
 
Old 'Theory of Metamorphism. 3 1 
 
 are intimately associated with gneiss. Thus you will 
 find, possibly, a mass of granite, with gneiss upon its 
 flanks arranged in a number of small wavy folds or 
 contortions. But granite is a crystalline rock, composed 
 of feldspar, quartz, and mica, and the old theory was 
 that the world at one time was in a state of perfect 
 igneous fusion ; but by and by, when it began to cool, 
 the materials arranged themselves as distinct minerals, 
 according to their different chemical affinities, and con- 
 solidated as granite. The great globe was thus composed 
 entirely of granite, at all events at the surface ; and 
 by and by, as cooling still progressed, and water by 
 condensation attempted to settle on the surface, that 
 surface still remaining intensely heated, water could not 
 lie upon it, for it was constantly being evaporated, and 
 filled the atmosphere ; but when the cooling became 
 more decided, and consolidation had fairly been estab- 
 lished, then water was able to settle on the surface of 
 the mass of granite. But as yet it could not settle quietly 
 like an ordinary sea of the present day ; for by reason 
 of the strong radiating heat, all the sea was kept in a boil- 
 ing state, constantly playing upon the granite that rose 
 above its surface here and there. The detritus thus 
 worn from the granite by the waves of this primitive 
 sea, was spread over its bottom; and because the 
 sea was boiling, the sediment did not settle down in 
 the form of regular layers, but became twisted and 
 
32 Gneiss of various Ages. 
 
 contorted in the manner I have described. All gneiss 
 therefore was conceived to be the original primitive 
 stratified rock of the world. 
 
 Subsequent research has shown that this theory will 
 not hold ; for this among other reasons, that we now 
 know gneissic rocks of almost all ages in the geological 
 scale. Thus in Scotland the gneissic rocks are of 
 Lawrentian and Silurian age; in Devon and Corn- 
 wall we have gneiss both of the Devonian and Carbon- 
 iferous ages. In the Andes, there are gneissic rocks of 
 the age of the chalk, and in the Alps, of the New red 
 Oolitic and Cretaceous series; and in 1862 I saw in 
 the Alps a species of gneiss of Eocene date, pierced by 
 granite veins, these strata being of the age of some of 
 the soft and often almost horizontal strata of the 
 London and Hampshire basins. It is therefore now 
 perfectly well known to geologists that the term Pri- 
 mitive, as applied to gneiss, is no longer tenable ; for 
 we find rocks of every age metamorphosed, and there- 
 fore the old theory has been abandoned. 
 
 The oldest rock, however, in the British Islands is 
 gneiss, but that originally was doubtless a common 
 stratified rock of some kind or other. In fact, as far 
 as the history told by the rocks themselves informs us, 
 we cannot get at their beginning at all, for all strata 
 are or have been made from the waste of rocks that 
 existed before ; and this proves that the oldest stratified 
 
Metamorphism. 33 
 
 rocks, whether metamorphosed or not, have a derivative 
 origin. In some manuals the word Primary is still 
 used as a convenient word to express the older strata, 
 but no one now means by the term that they were the 
 earliest rocks that ever existed, but simply that they 
 are the oldest rocks known. 
 
 Now I must briefly endeavour to give you an idea of 
 the theory of metamorphism. The simplest kind is of 
 that nature which I spoke of in last lecture, namely, 
 when an igneous is forced through or overflows a strati- 
 fied rock, and remaining for a long time in a melted 
 state, an alteration of the stratified rock in immediate 
 contact with it takes place. Thus, sandstone may, by that 
 process, become converted into quartz-rock, which is no 
 longer hewable, like ordinary sandstone, but breaks with 
 a hard and splintery fracture. It frequently happens 
 also that when you find an igneous rock which passes 
 through strata, the stratified rocks on each side for a 
 certain distance, say a few inches, are altered, and im- 
 perfect crystals of some kind or other are developed 
 where none existed before. Here then rocks are changed 
 or metamorphosed a short distance from the agent that 
 has been employed in effecting that metamorphism. 
 
 On a much larger scale, the sort of phenomena you 
 meet with in a truly metamorphic region are as follows. 
 In the midst of a tract of mica-schist, gneiss or other 
 altered rocks, a boss of granite (or one of its allies) 
 
 D 
 
34 Met amor fhism. 
 
 rises, like that for instance of Dartmoor or of the north 
 end of the Island of Arran. At a distance from the 
 granite, the beds may consist, perhaps, of unaltered 
 shale, or perhaps of slate, sandstone, and limestone. As 
 you approach the granite, the limestones become crystal- 
 line, and often lose all traces of their fossils, the sand- 
 stones harden and pass into quartz-rocks, and the shale 
 or slate loses its ordinary finely laminated texture, and 
 passes by degrees into mica-schist, or gneiss, in which 
 you find rudely alternating bands of quartz, feldspar, 
 and mica, often arranged in gnarled or wavy layers. 
 As you approach the granite still more closely, }^ou find 
 possibly that, in- addition to the layers of mica, quartz, 
 and feldspar, distinct crystals, such as garnet, stauro- 
 lite, schorl, &c. are developed near the points of contact, 
 both in the gneissic rock and in the granite itself. 
 
 It is not necessary for my argument that I should 
 describe these minerals, beyond putting you in posses- 
 sion of the fact that such minerals are developed under 
 these circumstances, and this is due to the influence of 
 metamorphism. 
 
 Now, if we chemically analyse a series of specimens 
 of clays, shales, slates, gneissic rocks and granites, it 
 is remarkable how closely the quantities of their ulti- 
 mate constituents will, in many cases, approach to each 
 other. In all of them silica would form by far the 
 largest proportion, say from 60 to 70 per cent. ; alumina 
 
. 
 
 Metamorphism . j j 
 
 would come next, and then other substances, such as 
 lime, soda, potash, iron, &c. would be found in smaller 
 varying proportions ; and what 1 now wish to impress 
 upon you is, that the minerals developed in the gneiss, 
 such as quartz, feldspar, mica, garnets, &c. are not 
 new substances introduced into the rock, by contact 
 with the granite, or by any other process ; but were all 
 developed under the influence of metamorphism from 
 materials that previously existed in the strata before 
 the metamorphic action began. Through some process, 
 in which heat played a large part, the rock having 
 been softened, and water present in all rocks under- 
 ground having been diffused throughout the mass 
 and heated, chemical action was set up, by which like 
 drew to like, and the matter that composed the clay, 
 shale, or slate, was enabled more or less to re-arrange 
 itself, according to its chemical affinities, and minerals 
 became visibly developed from elements that were in 
 the original rock. This is a short sketch of the theory 
 of metamorphism. I do not now attempt to give you 
 the details, as that would occupy a lecture in itself. 
 
 Now to produce metamorphism, heat is necessary, 
 to allow of internal movements by softening, without 
 which I do not see how complete re-arrangement of 
 matter and crystallisation could take place ; and though 
 it has always been easy to form theories about it, yet 
 so little is known with precision about the interior of 
 
 D 2 
 
3 6 Metamorphism . 
 
 the earth beyond a few thousand feet in depth, that 
 how to obtain the required heat is a difficulty. We 
 know, however, that strata which were originally de- 
 posited horizontally at the surface, have often de- 
 scended thousands of feet towards the centre of the 
 earth, by gradual sinking, and the simultaneous piling 
 up of newer strata upon them. The layer that, is 
 formed to-day is at the surface ; but neither the land 
 nor the sea-bottom are steady; the land is in places 
 slowly descending beneath the sea, and the sea-bottoms 
 are themselves descending and shifting also. It has 
 frequently happened, therefore, that for a long period 
 a steady descent over a given area has taken place, 
 and simultaneously with this many thousands of feet 
 of strata have by degrees accumulated bed upon bed. 
 Every one knows that as we descend into the earth 
 the temperature increases, whence, in the main, the 
 theory of central heat has been derived. Heat increases 
 about 1 for every 60 feet, and the temperature there- 
 fore at so great a depth as 14,000 or 20,000 feet, 
 to which it could easily be shown some strata have 
 sunk, is much higher than at the surface. Further- 
 more, strata that were deposited horizontally have 
 been frequently disturbed and thrown into rapid con- 
 tortions, or into great sweeping curves; and by this 
 means especially strata which once were at the surface 
 have been thrown, for aught we know to the contrary, 
 
Met amor phism. 37 
 
 twenty, thirty, or forty thousand feet downwards, and 
 therefore more within the influence of internal heat, 
 as for instance in the bed marked* fig. 3. I do not 
 wish you to understand that the globe is entirely filled 
 with melted matter that is a question still in doubt : 
 but, were this a course of lectures on theoretical geo- 
 logy, I think I could prove that the heat in the 
 interior of the globe sometimes in places apparently 
 capriciously eats its way towards the surface by the 
 fusion or alteration of parts of the earth's crust in a 
 manner not immediately connected with the more 
 superficial phenomena of volcanic action and thus it 
 may happen that strata which are contorted are in 
 places brought within the direct influence of great 
 internal heat. Under some such circumstances, you 
 will easily understand how stratified rocks may have 
 been so intensely heated, that they were actually 
 softened; and all rocks being moist (because water 
 that falls upon the surface percolates to unknown 
 depths towards the interior of the earth), chemical 
 actions were set going resulting in a re-arrangement of 
 the substances which composed the sedimentary rock. 
 Thus, common shale, or clay-slate, may have become 
 changed into a mass of gneiss. 
 
 This theory of re-arrangement leads me to another 
 question, connected with, but not quite essential to 
 my argument, as far as relates to physical geography, 
 
j 8, Metamorphism. 
 
 viz. what is the origin of granite, which in most ma- 
 nuals is classed as an igneous rock ? For my own part, 
 with some other geologists, I believe that in one sense 
 it is an igneous rock, that is to say, that it has been 
 completely fused. But in another sense it is a meta- 
 morphic rock, partly because it is impossible in many 
 cases to draw any definite line between gneiss and 
 granite, for they pass into each other by insensible gra- 
 dations ; and on the largest scale, both in Canada and in 
 the Alps, I have frequently seen gneissic rocks regularly 
 interbedded with less altered strata, the gneiss being so 
 crystalline that in a hand specimen it is impossible to 
 distinguish it from some granitic rocks, and even on a 
 large scale the uneducated eye will constantly mistake 
 them for granites. Another very important circum- 
 stance is that granite and its allies frequently occupy 
 the spaces that ought to be filled with gneiss or other 
 rocks, were it not that the gneiss has been entirely 
 fused. I therefore believe that granite and its allies 
 are simply the result of the extreme of metamorphism 
 brought about by great heat with presence of water. 
 
 One reason why it has been inferred that granite is not 
 a common igneous rock, is, that enveloping the crystals 
 of felspar and mica, there is generally a quantity of 
 free silica, not crystallised out in definite forms like the 
 two other minerals. Silica being far less easily fusible 
 than felspar, it seems clear that had all the substances 
 
Granite. 39 
 
 that form granite been merely fused together in a dry 
 state, the silica ought on partial cooling to have crystal- 
 lised first, whereas the felspar and mica have crystal- 
 lised first, and the silica not used in the formation of 
 these minerals wraps them round in an amorphous 
 form. Therefore it is said that it was probably held in 
 partial solution in extremely hot water, even after 
 crystallisation by segregation of the other minerals 
 had begun. This theory, now held by several distin- 
 guished physical and chemical geologists, seems to me 
 to be sound, especially as it agrees exceedingly well 
 with the metamorphic theory as applied to gneiss 
 granite being, as already stated, simply the result of the 
 extreme of metamorphism. In other words, when the 
 metamorphism has been so great that all traces of the 
 semi- crystalline laminated structure has disappeared, a 
 more perfect crystallisation has taken place, and the 
 result is a mass without any lamination in it. 
 
 Now in Scotland gneissic rocks and granites are: 
 extensively developed. The north-western Highlands 
 and the Hebrides consist, to a great extent, of a for- 
 mation which has been of late called Lawrentian, 
 named from a vast tract of gneissic rocks on the north 
 shore of the St. Lawrence, the geological age of which 
 was first determined by Sir William Logan. Above 
 them, in Scotland, other strata lie in the same district, 
 which, as they occur beneath the fossiliferous Silurian 
 
4O Scottish Formations. 
 
 series, are therefore supposed to be equivalent to the 
 strata called Cambrian in Wales, and have received 
 the same name. The Lower Silurian rocks come next in 
 the series, and form nine-tenths of the Highlands of 
 Scotland. They are chiefly gneiss and mica-schist, but 
 have thick masses of quartz-rock at the base, inter- 
 bedded with two bands of limestone, each of which con- 
 tains fossils, and by this their age has been ascertained. 
 
 Next, on the north-east coast, we have the Old red 
 sandstone, the Upper Silurian rocks which form such 
 an important part of the English strata being absent.* 
 
 Above the Old red sandstone lie the Carboniferous 
 rocks, consisting of Carboniferous limestone, and Coal- 
 measures, the limestone forming in Scotland but a very 
 small part of the series. These Carboniferous rocks lie 
 in the great valley between the Grampian range on 
 the north and the Lammermuir, Moorfoot, and Carrick 
 hills in the south. Besides these formations there are 
 others, in some of the Western Islands, such as Skye and 
 Mull, and also on the east of Scotland and elsewhere. 
 These consist of various members of the New red, Lias, 
 and Oolitic strata, which, however, form such a very 
 small part of Scotland, that they do not seriously affect 
 its physical geography, and therefore I shall at present 
 
 * This order for the north of Scotland was first established by Sir 
 E. Murchison. See ' Siluria' and Map of Scotland by Sir E. Murchison 
 and Mr. G-eikie. 
 
Arrangement in Sutherland. 41 
 
 say nothing about them, for I wish merely to put you 
 in possession of the facts connected with the greater 
 physical features of Scotland, omitting minor details. 
 
 Now, in the extreme north of Scotland, in Suther- 
 land and Caithness, the manner in which these strata lie 
 is shown in the following diagram. (See Map, line 4.) 
 
 Fig. 4. 
 
 In some of the Western Isles from the Lewes to 
 Bara, and in the north-west of Scotland from Cape 
 Wrath to Grairloch, the country to a great extent con- 
 sists of certain low tracts formed of Lawrentian gneiss 
 (No. 1) twisted and contorted in the most violent 
 manner. Upon this oldest gneiss the Cambrian rocks 
 (2) lie, rising often into high mountains, which face 
 the west in bold escarpments, and slope more gently 
 towards the east. These strata frequently lie at low 
 angles quite unconformably upon the older Lawrentian 
 gneissic rocks; the meaning of this being, that the 
 latter were disturbed, contorted, and extremely de- 
 nuded before the deposition of the Cambrian strata 
 upon them. The bottom beds of the latter consist of 
 conglomerate of rounded pebbles, derived from the 
 waste of this ancient Laurentian gneiss, which, there- 
 fore, is so old that it had been metamorphosed and was 
 
42 Scottish Formations. 
 
 land before the deposition of the Cambrian strata. 
 Upon these unaltered Cambrian beds, and again quite 
 unconformably, the Lower Silurian strata are placed in 
 the manner shown in the Diagram. The bottom beds 
 consist of quartz-rock and two beds of limestone (3), 
 the latter so altered that the fossils are sometimes with 
 difficulty distinguishable, even by those most skilled in 
 determining their nature. Then above the upper 
 limestone we have a vast series of beds of mica-schist 
 and gneissose rocks (4), mostly flaggy in the north- 
 western region, but in the eastern parts of Sutherland, 
 Aberdeenshire, &c. often so highly metamorphosed, 
 that they are in many respects very similar to the 
 more ancient Lawrentian gneiss. 
 
 Now these metamorphosed Silurian rocks, here and 
 there associated with great bosses of granite and syenite 
 (g) form by far the greater part of that extremely rocky 
 region known as the Highlands of Scotland, stretching 
 over brown heaths and barren mountain ranges, all the 
 way from Loch Eribol on the north shore far south 
 across the Grampians, to the Firth of Clyde on the west 
 and Stonehaven on the east. 
 
 In Sutherland as a whole the Silurian strata dip 
 eastward, and in Caithness we have the Old red sand- 
 stone (5) lying quite unconformably upon the Si- 
 lurian gneiss, and descending towards the sea. At its 
 base the Old red sandstone consists of conglomerate, 
 
South of the Grampians. 43 
 
 not formed merely of small pebbles like Fig. 5. 
 those of an ordinary shingle-beach, but fre- 
 quently of huge masses sometimes yards in 
 diameter, mingled with others of smaller 
 size. All of them have evidently been de- 
 rived from the partial destruction of those 
 ancient Silurian gneissic rocks (4) that 
 underlie the Old red sandstone. 
 
 Again, if you examine the Map of Scot- 
 land (line 5) you will find a broad band 
 of Old red sandstone running from Stone- 
 haven on the east coast to Dumbarton on 
 the west, and there also masses of con- 
 glomerate lie at the base as in No. 2, 
 fig. 5. Overlooking this broad band, the 
 gneissose mountains No. 1 rise high into 
 the air; still reminding the beholder of 
 that ancient line of coast, against which 
 the waves of the Old red sandstone period 
 beat, and from its partial waste formed 
 that boulder-beach that now makes the 
 conglomerates. We are thus justified in 
 coming to the conclusion that the North 
 Highlands generally, formed land before 
 the time of the Old red sandstone, the 
 Grampian mountains as a special range 
 forming a long line running from north-east 
 
44 Old Red Sandstone and 
 
 to south-west, the bases of its hills having been washed 
 by the waters which deposited the Old red sandstone 
 itself. 
 
 If you again examine the map you will find that 
 a vast tract of country, forming half the Lowlands, 
 stretches right across Scotland from north-east to south- 
 west, including the Firths of Tay and Forth, and all 
 the southern and eastern shores of the Firth of Clyde. 
 This area is occupied by Old red sandstone and rocks 
 of Carboniferous age (2 & 3, fig. 5), mostly stratified, 
 but partly igneous. To the south lie the heathy and 
 pastoral uplands known as the Carrick, Moorfoot, Pent- 
 land and Lammermuir hills, marked 1', which like 
 the Highlands are also chiefly formed of Silurian rocks, 
 but much less altered, and possessing nothing of a 
 gneissic character. The Carboniferous rocks and Old 
 red sandstone thus lie as a whole in a great hollow 
 between the Grampian and the Lammermuir ranges, 
 the coal-bearing strata consisting of alternations of 
 shale, sandstone, ironstone, limestone, and coal, mingled 
 with the volcanic products of the period. 
 
 Now how were the Carboniferous rocks formed ? 
 They consist of strata partly of fresh-water but chiefly 
 of marine origin, for not only are the limestones formed 
 chiefly of corals and shells, but many of the shales 
 also yield similar fossils. Beds of coal are numerous, 
 (whence the name Coal-measures, originally derived 
 
Carboniferous Rocks. 45 
 
 from the miners) and under each bed of coal there is 
 a peculiar stratum, which often, but not always, is of 
 the nature of fire-clay. Sometimes, it is called ' under- 
 clay,' this being the miners' term, on account of its 
 position beneath each bed of coal. Coal itself is well 
 known to consist of mineralised vegetable matter, and 
 when you examine the shales and sandstones associated 
 with it, you frequently find in them quantities of 
 vegetable remains, ferns, stems of reed-like plants 
 (Catamites), trunks of various trees, &c. When the 
 fire-clay is narrowly examined, you also generally find 
 in it a number of portions of plants called Stigmaria, 
 now known to be the roots of a fossil tree called Sigil- 
 laria, and this led Sir William Logan, Mr. Binney, and 
 other geologists to infer that the under-clay was the 
 original soil on which the plants grew, the decay and 
 subsequent mineralisation of which formed beds of coal. 
 
 Among those plants which are found in the coal and 
 its associated under-clay, and in the shale, may be enu- 
 merated the following genera: Sigillaria, Lepidodendron, 
 Ulodendron, Calamites, Halonia, &c., and numerous 
 genera of Ferns. 
 
 Now in the Scottish Coal-measures there are in 
 Edinburghshire 1 over 3,000 feet of coal-bearing strata, 
 so that the lowest bed of coal may be nearly three 
 thousand feet below the highest bed, in the centre of 
 the basin, where the strata are thickest. Most of them 
 
46 Carboniferous Rocks. 
 
 rise or f crop,' as miners term it, to the surface some- 
 where or other, this * out-crop ' being the result of 
 disturbance of the strata and subsequent denudation, 
 and it is by means of this disturbance and denudation 
 that we are enabled to estimate the thickness of the 
 whole mass of strata, and to prove that one bed lies 
 several thousands of feet below another. Now, as the 
 ' under-day ' contains roots, and was the soil on which 
 the plants grew, it is clear that the lowest bed of 
 coal was originally at the surface, and was formed by 
 the growth and decay of plants. After a time it seems 
 to have descended steadily and slowly, and other 
 strata were deposited upon it, sometimes in the sea, or 
 sometimes probably at the mouths of great rivers, 
 where a certain area was being filled with sediment. 
 By degrees a portion of the area, by filling up again, 
 became fit for the growth of terrestrial plants, 
 which plants decayed and formed another carbonaceous 
 stratum, that in its turn again sunk, and other strata 
 were deposited upon it. Vegetable growth again took 
 place, and so by intermittent sinkings and accumula- 
 tions a great number of strata were produced, terres- 
 trial, marine, estuarine and fresh-water, which by degrees 
 became a vast pile several thousands 'of feet thick. 
 The beds of vegetable remains were, probably, when first 
 formed, somewhat in the state of peat, and by immense 
 pressure and internal chemical changes, they in a long 
 
Igneous Rocks. 47 
 
 lapse of time became mineralised, while by still later 
 disturbance and denudation they are now in places ex- 
 posed to view. In this way the Coal-measures were 
 formed. 
 
 But in the Scottish area, during the formation of 
 part of the Old red sandstone and of the Coal-mea- 
 sures, many volcanoes were at work ; and thus, we 
 have dykes and bosses of feldspathic trap and green- 
 stone, and inter-stratifications of old lava streams, and 
 beds of volcanic ashes mingled with the common sedi- 
 mentary strata. These, being generally harder than 
 the sandstones and shales with which they are inter- 
 bedded, have more strongly resisted denudation, and now 
 stand out in hilly ranges like the Pentland and Ochil 
 Hills, or in craggy lines and bosses like Salisbury Crags, 
 the Lomond s of Fife, and the Grarlton Hills in Hadding- 
 tonshire, which give great diversity to the scenery, 
 without ever rising to the dignity of mountains. 
 
 Having fhus given a brief history of the mode of 
 formation of the more important Scottish formations, 
 you will already have begun to perceive what is the 
 cause of the mountainous character of the Highlands 
 and of the softer features of the Lowlands. It is 
 briefly this : that in very ancient geological times, 
 before the deposition of the Old red sandstone, the 
 Silurian rocks which form almost entirely the northern 
 
48 General Structure of Scotland. 
 
 half of Scotland, had already been metamorphosed and 
 greatly disturbed. Such metamorphic rocks, though as 
 a whole difficult of destruction, yet consist of inter- 
 mingled masses of different degrees of hardness, 
 whence the height of the mountains and their great 
 variety of outline. In the south of Scotland from 
 Gralloway to the coast of Berwickshire, the same 
 strata, forming the uplands of the Carrick, Moorfoot 
 and Lammermuir hills, have been equally disturbed, 
 but being comparatively unmetamorphosed, they are 
 less hard, and have been more worn by denudation, 
 whence their lower elevation. Then on the flanks of 
 the Highland mountains, and partly round the eastern 
 margin of what is now Scotland, the softer strata of 
 the Old red sandstone, in various subformations, were 
 deposited, formed partly, as the conglomerates testify, 
 from the waste of the older Silurian strata. In time, 
 the Old red sandstone period came to an end, and 
 above that series for it consists of several members, 
 according to present nomenclature, which lie uncon- 
 formdbly on each other the Carboniferous rocks were 
 formed. The whole were then again disturbed to- 
 gether, a disturbance not confined to Scotland only, 
 but embracing large European and other areas. In 
 this lecture, however, I have merely to show you how 
 these things affect the physical structure of Scotland. 
 But before the deposition of the Old red and Carbon- 
 
Relations of the Strata. 49 
 
 iferous series, there is reason to believe that a wide 
 and deep valley already existed between the Grampian 
 mountains and the Carrick, Lammermuir, and Moorfoot 
 range; and in this hollow the Old red sandstone was 
 deposited, partly derived from the waste of the Silurian 
 hills on the north and south. But by-and-by, as depo- 
 sition progressed, the land began to sink on the south, 
 and the upper strata of Old red sandstone overlapped 
 the lower beds, and began as it were to creep south- 
 wards across the Lammermuir hills, which, sinking still 
 further, were in turn invaded by the lower Coal-mea- 
 sures and Carboniferous limestone series. It appears, 
 therefore, from a consideration of all the circumstances 
 connected with the physical relations of the strata, that 
 the Coal-measures once spread right across the Lam- 
 mermuir range, and were united to the Carboniferous 
 strata that now occupy the north of England; thus, with 
 part of the Old red sandstone, covering the Silurian 
 strata of the south of Scotland. This unconformable 
 covering has, however, in the course of repeated denu- 
 dations, been removed from the greater part of that high 
 area, and now the Carboniferous strata are only found 
 in force in the great central valley through which flow 
 the rivers Forth and Clyde. 
 
 You will easily understand this if we refer to the sec- 
 tion, fig. 5, across the central valley of Scotland from 
 the Grampian mountains to the Lammermuir hills. 
 
 E 
 
50 Central Valley of Scotland. 
 
 The gneissic rocks (No. 1), with bands of Lime- 
 stone marked *, of the Highlands, pass under the Old 
 red sandstone (2), and rise again, highly disturbed, but 
 not much metamorphosed, in the Lammermuir hills (I'). 
 On these the Old red sandstone (No. 2) lies unconform- 
 ably, above which come the Carboniferous rocks No. 3, 
 lying in a wide broken and denuded synclinal curve. 
 The diagram is, however, too small to show these 
 breaks. The southern continuation of these strata 
 once spread over the Lammermuir hills in a kind of 
 anticlinal curve, in the manner shown by the dotted 
 lines on the diagram below No. 3'. 
 
 Now why is it that the Carboniferous and Old red 
 sandstone rocks have been specially preserved in the 
 great valley, and almost entirely removed from the 
 upland region of the Lammermuir hills ? The reason is 
 probably this. 
 
 When strata are thrown into a series of anticlinal and 
 synclinal curves it frequently happens that those parts 
 of the disturbed strata that are thrown downwards, so 
 as to form deep basin-shaped hollows as in the bed 
 or beds marked with an asterisk,* fig. 3, are by this 
 means saved from the effects of denudation, while the 
 upper parts of the neighbouring anticlinal curvatures 
 have been denuded away. 
 
 In other words, in one place the beds lay so deep that, 
 
Denudations. 5 1 
 
 being below the influence of the denuding agent, they 
 have escaped denudation, and the basin as geologists 
 term it remains ; and this is the reason why so many 
 coal-fields lie in basins. It is not, as used to be sup- 
 posed, that the beds were deposited in basins, but 
 that by disturbance, part of the strata have been thrown 
 into that form, and were saved from the effects of 
 denudation. Such basins are, therefore, equally com- 
 mon with all kinds of formations ; though, because they 
 rarely contain substances of economic value, they have not 
 obtained the same attention from geologists that Coal- 
 basins have received. In the case now under review, 
 it happens that the Old red sandstone and Carboniferous 
 rocks lie in the hollow, while the continuation of part of 
 the same strata that lay high in an anticlinal form, and 
 originally spread over the Lammermuir hills (3'), has 
 been removed by denudation; the reason being that 
 during frequent oscillations of land, relatively to the 
 level of the sea, the higher ground was much more often 
 above water than the lower part. To understand this 
 thoroughly let us suppose, for the sake of argument, 
 that the whole of this country was underneath the 
 waters of the ocean, and then let it be raised to a 
 certain extent above the level of the sea. Part of the 
 Lammermuir area, then covered with Coal-measures, 
 rose above the water, and was immediately subjected to 
 
 2 
 
5 2 Origin of Mountains. 
 
 the wear and tear of breakers on the shore, and of rain 
 and other atmospheric influences ; while, on the other 
 hand, that portion that Jay deep in the synclinal curve 
 was beneath the level of the sea, and thus escaped 
 denudation, because no wasting action takes place in 
 such situations. 
 
 By such geological accidents as these, the greater 
 features of Scottish scenery have been produced. The 
 Highlands are necessarily mountainous because they 
 are composed of disturbed rocks mostly crystalline; 
 which, having been often and long above water, have 
 been extremely denuded; such denudations having 
 commenced so long ago, that they date from before 
 the time of that extremely venerable formation, the 
 Old red sandstone, and have been repeated over and 
 over again down to the present day. Being formed 
 generally of materials of great but unequal hardness, 
 and associated with masses of granite, they have thus 
 been cut up into innumerable valleys, whence their 
 mountainous character; for mountains are rendered 
 rugged, less by disturbances of strata than by the 
 scooping out of the valleys. By mere disturbance of 
 strata, the land might rise high enough, but as our 
 mountain regions (and all others) now exist, it is by 
 a combination of disturbance of strata with extreme 
 denudation, that peaks, rough ridges, and all the cliffs 
 and valleys of the Highlands in their present form have 
 
The Highlands. 
 
 S3 
 
 been called into existence. Farther south the different 
 nature, both of the Silurian and newer rocks, coupled 
 with other geological accidents, have produced the 
 great valley, and the tamer but still hilly scenery of 
 the Southern Lowlands. 
 
54 
 
 LECTUEE III. 
 
 THE PHYSICAL STRUCTURE OF ENGLAND. 
 
 THE geology of England and Wales is much more com- 
 prehensive than that of Scotland, in so far that it 
 contains a great many more formations, and its features, 
 therefore, are more various. England is the very 
 Paradise of geologists, for it may be said to be in itself 
 an epitome of the geology of almost the whole of 
 Europe. Very few known geological formations are 
 absent in England, and when they are so, with few 
 exceptions, these are of minor importance. In some 
 countries larger than England the whole surface is 
 occupied by one or two formations, but here, we 
 find all the formations shown in the column (page 20) 
 more or less developed. Those of Silurian age lie 
 chiefly in the north of England in Cumberland and 
 Westmoreland, and, in the west, in Wales and Cornwall. 
 Above them lie the Old red sandstone and Devonian 
 rocks, occupying vast tracts in Herefordshire, Worces- 
 tershire, South Wales, and in Devonshire and Cornwall. 
 
England and Wales. 
 
 55 
 
 I" 3 
 
 g 1' 
 is 
 
 to "S 
 
 To S 
 
 65 
 
 *^ *~ 
 
 ^ is 
 
 ^5 O 
 
 O 
 
 ' 
 
 % 
 
 
 z e 
 
5 6 Lower Silurian Rocks. 
 
 Above the Old red sandstone comp the Carboniferous 
 limestone and the Coal-measures, which in South 
 Wales skirt the Bristol Channel, and stretch into the 
 interior, while in the north they form a great backbone 
 of country that reaches from the borders of Scotland 
 down to North Staffordshire and Derbyshire. Other 
 patches, here and there, rise from below the Secondary 
 strata of the heart of England, and skirt the older for- 
 mations in the west from Shropshire to Anglesey. 
 
 The general physical structure of our country from 
 the coast of Wales to the Thames, will be easily under- 
 stood by a reference to fig. 6 and to the following descrip- 
 tions, and this structure is eminently typical, explain- 
 ing, as it does, the physical geology of the chief part of 
 England south of the Staffordshire and Derbyshire hills. 
 
 The Lower Silurian rocks of Wales (No. 1, fig. 6) 
 and Cumberland consist chiefly of slaty and gritty 
 strata, accompanied by, and interbedded with, various 
 kinds of feldspathic lava and volcanic ashes, marked + , 
 and mingled with them there are numerous bosses and 
 dykes of greenstone, quartz-porphyry, and the like. 
 These last, by their superior hardness, have helped to 
 give that mountainous character to the western arts 
 of our island, now called North Wales and Cumberland. 
 In Pembrokeshire also, in a less degree, igneous rocks 
 are largely intermingled with the Silurian strata, helping 
 to form a very hilly country. 
 
Earliest Denudations. 57 
 
 Without entering into details respecting the minor 
 formations, known as the Lower and Upper Llandovery 
 beds, it is sufficient to state that the Cambrian and 
 Lower Silurian epoch ended in the British area by 
 disturbance and contortion of the strata, and their up- 
 heaval into land. This disturbance necessarily gave 
 rise to long-continued denudations of this earliest 
 English land, both by ordinary atmospheric agencies, 
 and also by the action of the waves of the sea of a 
 younger Silurian period, the evidence of which is seen 
 in the conglomerates of the Upper Llandovery beds, 
 which mingled with marine shells lie unconformably 
 on the denuded edges of the Cambrian and Lower Silu- 
 rian strata of the Longmynd, like an old consolidated 
 sea beach. Slow submergence then took place beneath 
 the Upper Silurian sea, in which the Upper Silurian 
 rocks themselves were gradually accumulated uncon- 
 formably on the Lower Silurian strata (2, fig. 6), till in 
 places they attained a thickness of from three to six 
 thousand feet. 
 
 Their uppermost strata then pass insensibly into the 
 newer series known as the Old red sandstone (3, fig. 6), 
 formed, if we include the entire formation, of beds of 
 red marl, sandstone, and conglomerate, which, with a 
 probable unconformable break in the middle, in turn 
 again pass upwards in some regions into the Carbon- 
 iferous limestone, which is overlaid in 'Wales and 
 
58 Carboniferous Rocks. 
 
 England by the Millstone grit and the Coal-measures.* 
 This Carboniferous limestone is entirely formed of sea 
 shells, encrinites and other organic remains, and attains 
 a thickness of two thousand five hundred feet in South 
 Wales and the south-west of England, and in Derby- 
 shire, where no man has ever seen its base, because 
 it rolls over in an anticlinal curve, it reaches even 
 a much greater thickness. The Millstone grit is in 
 South Wales 1,000 feet thick, and the true Coal- 
 measures, which are generally more or less of the 
 same nature as those that I described as occurring 
 in Scotland in the last lecture, are in Monmouthshire 
 and Glamorganshire not less than from 10,000 to 
 12,000 feet thick. The English Carboniferous rocks 
 differ from the Scottish beds in this, that in general 
 they have not been mixed with igneous interstrati- 
 fications, except in Northumberland and Derbyshire, 
 where the Carboniferous limestone is interbedded with 
 ashes and lava, locally in Derbyshire called toad-stones.' 
 In South Staffordshire and in Coalbrook Dale, &c., 
 there is a little basalt ; but in Glamorganshire and 
 Monmouthshire, where the Coal-measures are thickest, 
 no igneous rock of any kind occurs. There and else- 
 where in England the Coal-measures as usual consist 
 
 * This is not shown in fig. 6, but the Carboniferous limestone No. 4 
 is shown in fig. 7, lying, as it does in North Wales, unconformably on 
 Silurian rocks. 
 
Permian Rocks. 59 
 
 of alternations of sandstone, shale, coal, and ironstone ; 
 the coal everywhere being the remains of the decayed 
 plants that grew upon the soils of the period, in the 
 same way that I described them as growing in their day 
 on what is now the Scottish Coal-measure area. 
 
 Next in the series come the Permian rocks (5, fig. 8), 
 which however do not occupy so large a space in England 
 as materially to affect the larger features of the scenery 
 of the country. They form a narrow and very marked 
 strip on the east of the Coal-measures from Northum- 
 berland to Nottinghamshire, where they frequently 
 consist of certain beds of conglomerate and sandstone 
 at the base, above which lies a long, low, flat-topped 
 terrace of Magnesian limestone, the scarped edge of 
 which faces west, and overlooks the lower undulations 
 of the Coal-measure area. There are also certain other 
 patches of Permian rocks known as the Rothliegende* 
 here and there present on the borders of the North 
 Wales and Shropshire coal-fields. The same formation, 
 partly in the form of rough angular conglomerates, 
 also lies on the Silurian rocks of the Malvern hills, 
 and borders the coal-fields in the centre of England. 
 But though these conglomerates here and there form 
 
 * A German name pretty generally adopted over Europe, for strata 
 that were formerly called in England Lower new red sandstone. It is 
 used to prevent confusion between these strata and the true New red 
 sandstone, sometimes called the Bunter beds. 
 
60 Primary or Paleozoic Rocks. 
 
 prominent points in the landscape, such as Wars Hill 
 on the Malvern range, and Frankly Beeches in South 
 Staffordshire, they produce no marked general feature 
 in the physical structure of the country, and therefore I 
 say little about them. 
 
 The Permian beds form the uppermost members 
 of that Palaeozoic or old-life period, which begins in 
 England with the Cambrian rocks. The whole together 
 are sometimes called for the sake of convenience by the 
 old name of Primary strata. During the time they 
 were forming, this part of the world suffered many ups 
 and downs, accompanied by large denudations ; and at 
 the close of the Permian period, a disturbance of the 
 strata on the greatest scale marks the end of this 
 great Palaeozoic epoch over all Europe and more be- 
 sides. By this disturbance, which was acccompanied 
 by much contortion of the strata, a large part of what 
 is now England was heaved up and formed dry land, 
 to be again wasted and worn away by sea-waves and 
 rivers, and all the common atmospheric agencies. This 
 old land in great part consisted of what we now know 
 as Wales, and the adjacent counties of Hereford, Mon- 
 mouth, and Shropshire, of part of Devon and Cornwall, 
 Cumberland, the Pennine chain and all the moun- 
 tainous parts of Scotland. Around old Wales, and part 
 of Cumberland, and probably all round and over great 
 part of Devon and Cornwall, the New red sandstone 
 
New Red Sandstone. 6 1 
 
 was deposited. Part at least of this oldest of the 
 Secondary rocks was formed of the material of the 
 older Palse.ozoic strata, that had then risen above the 
 surface of the water, though it is not easy to trace 
 precisely the whole of its subdivisions to the waste of 
 special portions of the more ancient formations. 
 
 The New red sandstone series (No. 6, figs. 6 and 8) 
 consists in its lower members of beds of red sandstone 
 and conglomerate, more than a thousand feet in thick- 
 ness, and above them are placed red and green marls, 
 chiefly red, which in GrermaDy go by the name of the 
 Keuper strata, and in England are called the New red 
 marl. The whole is often called the Trias. These 
 formations fill the Vale of Clwyd in North Wales, and 
 in the centre of England range from the mouth of the 
 Mersey round the borders of Wales to the estuary of 
 the Severn, eastwards into Warwickshire, and thence 
 northwards into Yorkshire and Northumberland, along 
 the eastern border of the Magnesian limestone. In the 
 centre of England the unequal hardness of its subdi- 
 visions sometimes gives rise to minor escarpments, most 
 of them looking west, over plains and undulating ground 
 formed of softer strata. In the New red sandstone of 
 Great Britain there are few relics of life, except at the 
 very top where it passes into the Lias. They are 
 plentiful in the Muschelkalk, which forms the middle 
 part of the series in Germany, but is absent with us. 
 
62 Lias and Oolite. 
 
 The Lias series (7 and 8, fig* 6), conformably suc- 
 ceeds the New red sandstone. The Lias constitutes 
 a well defined belt of strata, running continuously from 
 Lyme Eegis on the south-west through the whole of 
 England, to Yorkshire on the north-east, and is an 
 extensive series of alternating beds of clay, shale, and 
 limestone, with occasional layers of jet. The Lias is 
 rich in the relics of ancient life, and it is in these strata 
 that those remarkable marine reptiles, the Ichthyosauri 
 and Plesiosauri, occur so plentifully. The unequal 
 hardness of the clays and limestones of the Liassic 
 strata causes some of its members to stand out in dis- 
 tinct minor escarpments, often facing west and north- 
 west. The Marlstone (8, fig. 6) forms the most pro- 
 minent of these, and overlooks the broad meadows 
 of lower Lias clay that form much of the centre of 
 England. 
 
 Conformable to and resting upon the Lias are the 
 various members of the Oolitic series (9 and 10, fig. 6). 
 That portion termed the Inferior Oolite occupies the 
 base, being succeeded by the Great or Bath Oolite, 
 Cornbrash, Oxford clay, Coral Eag, Kimeridge clay and 
 Portland beds. These, and the underlying formations, 
 down to the base of the New red sandstone, constitute 
 what geologists term the Older Secondary formations, 
 and all of them, from their approximate conforma- 
 bility one to the other, occupy a set of belts of variable 
 
Pur beck and Wealden. 63 
 
 breadth, extending from Devon and Dorsetshire north- 
 wards, through Somersetshire, Gloucestershire, and 
 Leicestershire, on to the north of Yorkshire, where 
 they disappear beneath the German Ocean. 
 
 When the Portland beds had been deposited (forming 
 the top of 10, fig. 6), the entire Oolitic series in what 
 is now the south and centre of England, and much 
 more besides in other region^, was raised above the 
 sea-level and became land ; and because of this ele- 
 vation, in the Isles of Purbeck, Portland and the Isle 
 of Wight, and in the district known as the Weald, 
 there is evidence of a state of affairs common in all 
 times of the world's history, but from causes that it 
 would take long to enumerate, very unusual as far as 
 preserved strata are concerned. In fact, we have here 
 a series of beds, consisting chiefly of clays, sands, sand- 
 stones, and shelly limestone, indicating by their fossils 
 that they were accumulated in an estuary where fresh- 
 water and occasionally brackish-water and marine 
 conditions prevailed. The position of these beds with 
 respect to the Cretaceous strata, you will find in fig. 10, 
 p. 78, marked w, h, and to prove that they are inter- 
 mediate in date to the Oolites and Cretaceous rocks, 
 I may mention that in the Isle of Purbeck, they are 
 seen lying between the two. The Wealden and Pur- 
 beck beds, indeed, represent the delta of an immense 
 river, which in size may have rivalled the Ganges or 
 
64 Pur beck and Wealden. 
 
 the Mississippi, and whose waters carried down to 
 its mouth land-plants, small mammalia, and great 
 terrestrial reptiles, and mingled them with the remains 
 of shells, fish, crocodiles, and other forms native to its 
 waters. I do not by any means wish you to understand 
 that this immense river was formed simply by the 
 drainage of the small territory we now call Great 
 Britain. I do not indeed quite know where the mass 
 of the continent lay through which it ran and which 
 it drained, but I do know that England formed a part 
 of it, and that in size it that continent must have 
 been far larger than Europe and probably as large as 
 Asia, or the great continents of North or South America. 
 I must, however, explain how we know that the 
 Wealden series were accumulated under fresh-water 
 conditions, and as a river deposit. The proof lies partly 
 in the nature of the strata, but chiefly in the nature of 
 the organic remains contained in them. The fish give 
 no positive proof, but a number of Crocodilian reptiles 
 give more conclusive evidence, together with the 
 shells, most of them being of fresh-water origin, such as 
 Unio, Paludina, Planorbis, Limnaaa, Physa, and such 
 like, which you may find living in many a river, pond, 
 or canal of the present day. Some of these are so very 
 like existing species that it requires all the skill of 
 the accomplished paleontologist to tell that there is any 
 difference between them. But now and then we find 
 
Cretaceous Rocks. 65 
 
 bands of marine remains, not confusedly mixed with 
 the fresh-water deposits, but interstratified with them ; 
 showing that at times the mouth and delta of the river 
 had sunk a little, and that it had been invaded by the 
 sea, so that oysters and other salt-water mollusca lived 
 and died there. Then by gradual changes it was again 
 lifted up, and became an extensive fresh-water area. 
 It is important to mention these circumstances, because 
 the nature of some of these half consolidated strata 
 exercises a considerable effect on the amount and nature 
 of the denudation of the rocks in the south-east of 
 England, and consequently upon its scenery. \ 
 
 This episode at last came to an end, by the complete 
 submergence of the Wealden area ; and upon these 
 fresh-water strata a set of marine sands and clays were 
 deposited, and upon these thick beds of pure white earthy 
 limestone, all belonging to the Cretaceous period. The 
 lowest of these formations is known as the Lower 
 greensand (s d, fig.10, p. 78) ; then comes the clay of the 
 Grault, above which lies the Upper greensand. Then 
 resting upon the Upper greensand comes the vast mass 
 of Chalk (c, fig. 10, and No. 11, fig. 6), the upper por- 
 tion of which contains numerous bands of interstratified 
 flints which originally were mostly sponges, since sili- 
 cified. The cbalk strata, where thickest, are from one 
 thousand to twelve hundred feet in thickness. The 
 upheaval of the Chalk into land brought this epoch to 
 
 F 
 
66 Eocene Beds. 
 
 an end, because those conditions that had contributed 
 to its formation ceased in our area, and, as the upper- 
 most member of the Upper Secondary rocks, it closes 
 the record of Mesozoic times in England. 
 
 This brings us to the last divisions of the British strata, 
 of which I shall speak in this lecture. These were 
 deposited on the Chalk, and are termed Eocene forma- 
 tions (No. 12, fig. 6, p. 55). At the base they consist of 
 marine and estuary deposits, known as the Thanet sand 
 and Woolwich and Eeading beds. These lie below the 
 London Clay and form the outer border of the London 
 basin. The same strata are found in the Isle of Wight, 
 and in part constitute the Hampshire basin. In the 
 Woolwich and Eeading beds we have in places the same 
 kind of alternations of fresh-water and marine shells 
 that I mentioned to you as occurring in the Wealden 
 and Purbeck strata; but with this difference, that 
 though the shells belong mostly to the same genera, 
 they are altogether of different species the old fresh- 
 water life is replaced by the new. Upon the London 
 Clay, which is a marine formation, were deposited the 
 Bracklesham and Bagshot beds. Upon these were 
 formed various newer fresh-water strata occasionally 
 interbedded with thin marine bands, the whole evi- 
 dently accumulated at the mouth of another great river. 
 I may mention that the word Eocene was first used 
 by Sir Charles Lyell tc express the dawn or begin- 
 
Mountains and Plains. 67 
 
 ning of recent life, or of that kind of life that exists 
 in the world at the present day. It is applied to 
 all the members of the lower Tertiary strata. 
 
 Now I think I have given you an idea of the series 
 of the larger and more solid geological formations that 
 are concerned in producing the physical structure of 
 England, and I will now endeavour to show you, by 
 the help of the diagram fig. 6, the part that these 
 formations play in producing the scenery of the 
 country. 
 
 First, then, in the far west, in Devon and Cornwall, 
 and in Wales, also in the north-west in Cumberland, 
 and in the Pennine chain which stretches from North- 
 umberland to Derbyshire, we have what forms the 
 mountainous and more hilly districts of England and 
 Wales. 
 
 In Wales the country is essentially of a mountainous 
 character; and the middle part of England, such as 
 Staffordshire, Worcestershire, and Cheshire, may be 
 described as flat and undulating ground sometimes 
 rather hilly. But as a whole, these midland hills are 
 insignificant when considered upon a large scale, for 
 when viewed from any of the mountain regions in the 
 neighbourhood, the whole country below appears like 
 a vast plain. To illustrate this let us imagine any 
 one on the top of the granitic or gneissic range of the 
 Malvern Hills (g, fig. 6), which have something of a 
 
 F 2 
 
68 Table-Lands and Plains. 
 
 mountainous character, and let him look to the west : 
 then, as far as the eye can reach, he will see hill after 
 hill stretching far into Wales (1 to 3, fig. 6) ; and if he 
 cast his eye to the north-east, he will there see what 
 seem to be interminable low undulations, almost like 
 perfect plains; while to the east lies a broad flat 
 (6 to 8) through which the Severn flows, bounded by 
 a flat-topped escarpment (9) rising boldly above the 
 plain, formed of the Oolitic formations which consti- 
 tute so large a part of Gloucestershire. These, as the 
 Cotswold Hills, form a high table-land, overlooking on 
 the west a broad plain of Lias clay and of New red 
 marl. This Oolitic escarpment stretches in a more 
 or less perfect form from the extreme south-west of 
 England northward into Yorkshire ; but it is clear 
 that the Oolitic strata were not originally deposited 
 in the scarped form they now possess, but once spread 
 continuously over the plain far to the west, and in all 
 probability only ended where the Oolitic seas washed 
 the land formed by the more ancient disturbed Palaeo- 
 zoic strata. Indeed I firmly believe that the Lias 
 and Oolites entirely surrounded this old land, passing 
 westwards through what is now the Bristol Channel 
 on the south, and the Dee and Mersey on the north. 
 They have only a slight dip to the south-east, and 
 great denudations having taken place, a large part 
 of them, miles upon miles in width, has been swept 
 
Denudation and 'Table-Lands. 69 
 
 away, probably partly by marine denudation ; and thus 
 it happens that a bold escarpment, once in part at 
 least an old line of Coast cliff, overlooks those central 
 plains of England, from which so vast an extent and 
 thickness of Lias and Oolite have been removed. 
 
 An inexperienced person standing on the plain near 
 Cheltenham or Wotton-under-edge would scarcely ex- 
 pect that when he ascended the Cotswold Hills, from 
 800 to 1,200 feet high, he would find himself on a 
 second plain (9, fig. 6) ; that plain, however, being a 
 table-land, in which here and there deep valleys have 
 been scooped, chiefly by the aid of running water.* 
 If you go still farther to the east, and pass in succession 
 all the outcrops of the different Oolitic formations (some 
 of the limestones of which form minor terraces), you 
 come to a second escarpment (1 1, fig. 6) formed of the 
 Chalk, which in its day also spread far to the west, 
 covering somewhat unconformably the half-denuded 
 Oolites, till it also abutted upon the ancient land formed 
 of the Palaeozoic strata of Wales. This also has been 
 partly denuded, and so we have another great feature, 
 in a bold escarpment of chalk which stretches from the 
 south-west of England into Yorkshire. 
 
 The Eocene strata, which lie above the Chalk, in their 
 day also extended much farther to the west, because 
 
 * Such valleys are necessarily omitted on so small a diagram, and 
 the minor terraces on the plain, especially such as 7, are exaggerated. 
 
7<D 'Table-Lands and Plains. 
 
 here and there at the extreme edge of the escarpment 
 of chalk you find outlying fragments of them. The 
 proof of this original extension westward is shown in 
 the following diagram. 
 
 Fig. 7. 
 
 1. Chalk. 2. The main mass of the Eocene beds. 2'. Outlying 
 patch of Eocene beds near the edge of the escarpment. 
 
 It is impossible that these outliers could have been 
 originally deposited on this edge of chalk and not on 
 the other strata that lie west of the escarpment, and 
 therefore they originally extended westward, and with 
 the Chalk, have been denuded backwards, till they 
 occupy their present area. But the Eocene beds 
 being formed of soft strata chiefly clays and sands 
 though they make undulating ground, form no bold 
 scenery, but rest upon the table-land or in depressed 
 areas somewhat in the manner shown at 12 in fig. 6. 
 
 Such is the general manner in which part of our 
 country has attained its present form. The whole of 
 the west of England, that is to say, of Wales, and part 
 of the north, consists of Palaeozoic strata, viz. : Cambrian, 
 and Silurian with all its igneous interstratifications, 
 Old red sandstone, the Carboniferous series, and the 
 
Mountains of Wales y &c. 7 1 
 
 Permian rocks. All these have been exceedingly dis- 
 turbed and extensively denuded. They are formed 
 of beds of variable hardness some of them being of 
 a slaty character, and others of masses of exceedingly 
 hard igneous rocks, which attain in some instances a 
 thickness of two or three thousand feet. You will, 
 therefore, easily understand how it happens that with 
 disturbed and contorted beds of such various kinds, 
 those great denudations which commenced as early 
 as the close of the Lower Silurian period, and have 
 been continued 'intermittently ever since, through 
 periods of time so immense that the mind refuses to 
 grapple with them, you will, I repeat, easily see how 
 the outlines of the country have assumed such exceed- 
 ingly varied and often rugged outlines as those which 
 Wales, Cumberland, and in a less degree parts of 
 Devon and Cornwall, now present. 
 
 But I have said that the Secondary and Lower Ter- 
 tiary strata have not been disturbed nearly to the same 
 extent #s the Palaeozoic or Primary formations anywhere 
 in England. Though occasionally traversed by faults, 
 yet with rare exceptions most of the strata have 
 been elevated above the water without any bending 
 or contortion on a large scale. What has chiefly taken 
 place was a slight uptilting of the strata to the west, 
 which, therefore, all through the centre of England, 
 dip as a whole slightly but steadily to the east and 
 
72 Effects of Disturbance, &c. 
 
 south-east. This is evident from the circumstance that 
 on the Cotswold hills the lowest Oolitic formation 
 (Inferior Oolite, No. 9, fig. 6) forms the western edge of 
 the Table-land, while, in spite of a few minor escarp- 
 ments that rise on the surface of the upper plain, the 
 higher Oolitic beds that dip below the Cretaceous strata 
 are at a lower level than the Inferior Oolite at the 
 edge of the plateau, as shown in fig. 6. 
 
 The result, then, of the great disturbance and denu- 
 dation of the Palaeozoic strata, and of the smaller dis- 
 turbance and denudation of the Secondary rocks, is, 
 that the general features of England present masses of 
 Palaeozoic strata forming a group of mountains in the 
 west, then certain undulating grounds and plains com- 
 posed of New red sandstone and Lias clay, and then 
 two great escarpments, the edges of table-lands, which 
 rise in some places to a height of more than a thousand 
 feet; the western one being formed of Oolitic, and 
 the eastern of Cretaceous strata, which, in its turn, is 
 overlaid by the Eocene series, comprising the London 
 and Hampshire basins. See fig. 6. 
 
 Again, if we construct a section from the Menai 
 Straits, across Snowdon and over the Derbyshire hills 
 to the east of England, the arrangement of the strata 
 may be typified in the following manner (fig. 8 and 
 Map, line 8). In the west, rise the older disturbed 
 Palaeozoic strata, Nos. 1 to 3, which form the mountain 
 
Section across England. 73 
 
 region of Wales. On the east of these 
 lies an upper portion of the Palaeozoic 
 rocks, 4, consisting of Carboniferous rocks 
 less disturbed than the underlying Si- 
 lurian beds on which they lie uncon- 
 formably. Then in Cheshire, to the east 
 of the Dee, lie the great plains of New 
 red sandstone 6, and these beds form 
 plains because they consist of strata that 
 have never been much disturbed, and 
 the beds of which are soft and easily de- 
 nuded. Then more easterly, from under 
 the flat strata of New red sandstone, the A 
 
 disturbed Coal-measures again rise, to- 
 gether with the Millstone grit and Car- 
 boniferous limestone forming the Derby- 
 shire hills, 4'. These strata dip first to 
 the west, underneath the New red sand- 
 stone, and then roll over to the east, 
 forming what is called an anticlinal curve, 
 the limestone being in the centre, and the 
 
 Millstone grit on both sides dipping west 
 and east; and above the Millstone grit 
 come the Coal-measures, also dipping west 
 and east. Together they form the southern 
 part of the Pennine chain which stretches 
 northward into Northumberland, and is 
 
74 Disturbance and Denudation. 
 
 also directly united to the Cumberland mountains on 
 the west. Then upon them, very little disturbed, 
 dipping easterly but at low angles, we have, first, a low 
 escarpment of Magnesian limestone 5, then the New 
 red sandstone and Lias plains 6 and 7, which are 
 covered to the east by the Oolite 9, forming an escarp- 
 ment, the latter being overlaid by the Chalk 1 1 ; but 
 in this case, the Oolitic strata being much thinner, do 
 not form the same bold table-land that they do in 
 Gloucestershire and in the more southern parts of 
 England. As shown in the diagram (fig. 8), the Creta- 
 ceous rocks also rise in a tolerably marked escarpment. 
 Further north the same grand general features pre- 
 vail. If a section were drawn across England from the 
 Cumberland mountains to Bridlington Bay, the effect 
 would be much as if the Lancashire and Derbyshire 
 Carboniferous hills were added on to the east of North 
 Wales, without the intervention of the New red sand- 
 stone and marly plains of Cheshire, for all across the 
 Palaeozoic rocks from Whitehaven into western York- 
 shire it is either mountainous or hilly. Then come the 
 New red and Liassic plains, above which rises the great 
 Oolitic escarpment, that stretches from the Humber 
 to the coast south and east of the Tees, and there 
 the Oolitic series, becoming harder and thicker, attain 
 great importance, and rise into scarped hills, as bold 
 as the Cotswolds. 
 
The Weald. 75 
 
 If we examine the country farther to the south-east, 
 in the Weald of Kent and Sussex, we generally find a 
 plain, bounded by chalk hills on the north, south, and 
 west, while the plain itself surrounds a series of undu- 
 lating hills in the centre. The whole of this Wealden 
 area, in fact, forms a great amphitheatre, on the outside 
 rim of which the Chalk rises in exceedingly bold es- 
 carpments, forming what are known as the North and 
 South Downs. On the east it is bounded by the sea. 
 There cannot be any doubt but that the Chalk and 
 the underlying formations of Upper greensand, (zault, 
 Lower greensand, and Weald clay originally extended 
 fairly across all the area of the Weald for a breadth of 
 from twenty to forty miles from north to south, and 
 nearly eighty from east to west. This vast mass, many 
 hundreds of feet thick, has been swept away, according 
 to the general opinion, by the wasting power of the 
 sea, but I believe to a great extent also by atmospheric 
 agencies: so much so, indeed, that I am convinced 
 that all the present details, great and small, of the 
 form of the ground are due to the latter. The result 
 of this is the great oval escarpment of Chalk sur- 
 rounding the Wealden area, rising steeply above the 
 plain, which is composed of strata termed the Weald 
 clay, from beneath which the Hastings sands crop out, 
 forming a central nucleus of hilly ground, in the manner 
 shown in the following diagram, the height of which 
 
7 6 The Weald. 
 
 is prodigiously exaggerated so as to bring the features 
 prominently before the eye. 
 
 Fig. 9. 
 
 a a Upper Cretaceous strata, chiefly Chalk, forming the North and 
 South Downs; b b minor escarpments of Lower greensand ; cc "Weald 
 clay, forming plains ; d, hills formed of Hastings sand and clay. The 
 Chalk, &c. once spread across the country, as shown in the dotted lines. 
 
 Let us endeavour to realise how such a result may 
 have been brought about. The prevalent idea that the 
 Wealden area once formed a vast oblong bay, of which 
 the Chalk hills were the coast cliffs, is exceedingly 
 tempting ; for, standing on the edge, for instance, of 
 the North Downs near Folkstone, and looking south- 
 west across the Romney marshes, it is impossible not to 
 compare the great flat to a sea overlooked by all the 
 bays and headlands, which the winding outlines of the 
 Chalk escarpment are sure to suggest. And in less 
 degree the same kind of impression suggests itself 
 wherever one may chance to stand on the edge of the 
 chalk Downs all the way from Folkstone to Alton and 
 Petersfield, and from Petersfield to Eastbourne. For 
 years, with others, I held this view ; but of late I have 
 begun to feel that it is not easily tenable, though it is 
 perhaps not very easy completely to disprove it, especially 
 
Denudation. 77 
 
 to those who have long been accustomed to, and have 
 never before doubted, the commonly received hypothesis. 
 If the Weal den area were lowered into the sea just 
 enough to turn the Chalk escarpments into cliffs (see 
 Map and fig. 10), we should have the following general 
 results. Let the line a 6 represent the present sea level, 
 and the lines sss the level of the sea after depression ; 
 then so far from the area presenting a wide open sea, 
 where heavy waves could play between the opposite 
 Downs, we should have an encircling cliffy coast of 
 chalk c ; the base of which, unlike all coasts, is at 
 very unequal levels. This land would be formed of 
 two narrow strips of country, one on the south at least 
 60, and the other on the north not less than 100 miles 
 long, both of which would project eastward from the 
 Chalk of Hampshire, and form what we now call the 
 North and South Downs. These hills generally rise 
 high above the Eocene strata that skirt them on the 
 north and south, which under the supposed circum- 
 stances would be covered by sea, while the scarped cliffs 
 of Chalk, as shown on the diagram, would overlook a 
 sea-covered plain of Grault g ; outside of which, near the 
 shore, would be a long ridgy island of Lower green- 
 sand s d, which at present, round part of the country, 
 rises into an escarpment in places higher than the 
 Downs themselves. Then again there would be a space 
 of sea where the flats of Weald clay w now lie; 
 
Effects of Submergence. 
 
 I 
 
 ; 3 
 
Marine Denudation. 79 
 
 inside of which would lie an island, or rather group of 
 islands, formed of the Hastings sand series h h. This 
 form of ground would certainly be peculiar, and ill 
 adapted for the beating of a powerful surf, so as to pro- 
 duce on one side only, the cliffy escarpment that forms 
 the inner edge of the oval of Chalk. Further, if the 
 area had been filled with sea, we might expect to find 
 traces of superficial marine strata of late date, as in 
 other parts of England, scattered across the surface 
 between the opposite downs cc. But none of these 
 traces exist. On the contrary, the underlying strata 
 of the Cretaceous and of the Wealden series everywhere 
 crop up and form the surface of the ground, except 
 where here and there near the Chalk escarpments they 
 are strewn with a few flints, or where they are covered 
 by fresh-water sands, gravels, and loams of the ancient 
 rivers of the country. 
 
 I suspect, therefore, that the form of the ground in 
 the Wealden area which has been attributed to marine 
 action has been mainly brought about by the running 
 water of rivers. One great effect of marine denudation 
 when prolonged over periods of enormous length, is to 
 produce extensive plains like the line 66, fig. 14, p. 
 140 ; for, the result produced by the wasting power 
 of breakers is to plane off as it were the asperities of 
 the land, and reduce it to its own average tidal level. 
 Suppose the curvature of the various formations across 
 
8o Atmospheric Denudation 
 
 the Wealden area to be restored by dotted lines as 
 in the following figure, No. 11, which is very nearly 
 on a true scale. Then let the upper part of the curve 
 be planed across in the manner explained in a subse- 
 quent lecture, p. 141, the newly-planed surface, slightly 
 inclined towards the interior, being represented by the 
 line p p. Against this line the various masses of the 
 Hastings sand h h, Weald clay w, the Lower greensand s, 
 the Grault g, and the Chalk and Upper greensand c, would 
 crop up. Then I believe it to be possible, and even 
 probable, that by aid of the running water of streams, 
 large parts of these strata might be cut away, so as to 
 produce in an immense length of time the present con- 
 figuration of the ground. If it were not so we would 
 expect that the rivers of the Wealden area should all 
 flow out at its eastern end, where the ground is now 
 low, and looks out upon the sea, and towards which 
 the long plains of Grault and Weald clay directly 
 lead. But this, except with certain rivulets, is so far 
 from being the case, that some streams rise close 
 to the sea coast and flow westward. If such a plain 
 as pp once existed, it is easy to understand how 
 the rivers might in old times have flowed from a 
 low central watershed to the north and south across 
 the top of Chalk at elevations at least as high as, 
 and perhaps even a little higher than the present 
 summit-levels. Then, as by their action the general 
 
of the Weala. 
 
 81 
 
8 2 Denudation 
 
 level of the inner country was being partly reduced, 
 they would cut north and south channels through the 
 chalk downs as we now see in the Stour, the Medway, 
 the Dart, the Mole, the Wey, which run athwart the 
 North Downs, and the Arun, the Adur, the Ouse, and 
 the Cuckmare, which, through gaps in the South Downs, 
 flow south. On any other supposition it is not easy 
 to understand how these channels were formed, unless 
 they were produced by fractures or by marine denuda- 
 tion, of neither of which is there any direct proof.* 
 Through most of these gaps no known faults run of any 
 kind, and the whole line of the Chalk is singularly 
 destitute of fractures. We get a strong hint of the 
 probability of the truth of this hypothesis of denu- 
 dation in the present form of the ground. Thus after 
 the formation of the marine plain pp, the Chalk being 
 comparatively hard has only been partly denuded, and 
 now stands out as a bold escarpment in the Downs. The 
 soft clay of the Grault has been more easily worn away, 
 and forms a hollow or plain. The Lower greensand, 
 full of hard bands and ironstone, more strongly resisting 
 
 * This kind of argument was first applied by Mr. Jukes to explain 
 the behaviour of some of the rivers of Ireland, and he then said that it 
 might possibly apply to the Weald. Geol. Journal, 1 862, vol. xviii. p. 378. 
 The rejection of the old hypothesis of the common marine denudation of 
 the Weald has been gradually forcing itself on Mr. Drew, Mr. Foster, 
 and other officers of the geological survey who mapped the area, and 
 in these remarks, in some degree, I express their opinions as well as 
 my own. 
 
of the Weald. 83 
 
 denudation, forms a second range of scarped hills over- 
 looking the more easily wasted Weald clay, which forms 
 a second broad plain, from under which rises the harder 
 subdivisions of the Hastings sands forming the un- 
 dulations seamed by brooks of the central hills of Ash- 
 down Forest, and other places. The absence of flints 
 over nearly the whole of the Wealden area, excepting 
 near the Downs, is easily explained by this hypothesis, 
 for the original marine denudation had removed all 
 the Chalk, except near the margin, long before the river 
 denudations which commenced the escarpments began. 
 
 Given sufficient time, I see no difficulty in this result. 
 But the question arises, how much time in a geological 
 sense can be given ? 
 
 It is well known that, excepting for a few feet close 
 upon the coast, this southern part of England was not 
 depressed beneath the sea during the great icy period of 
 the Drift. It has, therefore, been above water for a 
 very long time. On the edge of the North Downs 
 there are certain fragmentary outliers described by 
 Mr. Prestwich. These by some persons have been 
 supposed to be outliers of the lower Eocene strata 
 called the Woolwich and Eeading beds, but Mr. Prest- 
 wich considers them to belong to the lowest part of the 
 Crag. 
 
 If they belong to any part of the Eocene series, then 
 the denudation of the Weald that produced its present 
 
 G 2 
 
84 Denudation of the Weald. 
 
 form may have been going on ever since the close of 
 the Eocene period, that is to say, all through the 
 Miocene and subsequent epochs. Those who are ac- 
 quainted with Continental geology will realise the 
 meaning of this when they consider that it implies a 
 lapse of time far longer than it has taken to form 
 the labyrinthine network of valleys cut into the great 
 table-land of the Rhine and Moselle, or more striking 
 still, to form the whole range of the Jura, and all the 
 lowlands of Switzerland that lie between those moun- 
 tains and the Alps. On the other hand, if the outliers on 
 the chalk escarpment west of Folkestone be parts of 
 the earlier Crag beds, then the bay-like denudation of 
 the Weald has probably entirely taken place since that 
 epoch ; implying another lapse of time so long, that by 
 natural processes alone, in rough terms, half the animal 
 species in the world have disappeared and been as slowly 
 replaced by others. This may mean little to those who 
 still believe in the sudden extinction of whole races of 
 life ; but to me it signifies a period analogous to the 
 distance of a half-resolved nebula, so vast, that if it 
 were possible to express it in figures the mind would 
 refuse to grasp its immensity. 
 
 I have gone so far into details on the point because 
 the c Denudation of the Weald ' has given rise to much 
 theorising by several distinguished authors, and I wish 
 to shew the reasons why I think that the amphitheatre- 
 
Isle of Wight. 85 
 
 like form of the area and the escarpment of the chalk 
 are not directly due to marine denudation or the beating 
 of sea waves, but rather, that the harder outer crust of 
 the chalk that once cased the anticlinal curve having 
 been planed off by marine denudation, and by sub- 
 sequent elevation, a table-land having been formed, the 
 softer rocks below that cropped up to the surface of 
 this plane were then attacked by running water, and 
 worn away so as to form the hills and valleys of the 
 district including the great escarpments of the North 
 and South Downs. 
 
 Though the Secondary and older Tertiary strata gene- 
 rally lie flat or dip at low angles, yet in one instance 
 they have been very considerably disturbed ; for on a 
 line which runs through the Isle of Wight and the Isle 
 
 Fig. 12. 
 
 Solent 
 
 of Purbeck they stand fairly on end. Those who are 
 familiar with the Isle of Wight will remember that 
 from east to west, or from White Cliff Bay to Alum 
 Bay, there is a long range of Chalk hills c, the strata 
 
86 Denudation 
 
 of which dip towards the north, and are overlaid by 
 the older Tertiary strata e, that is to say the Woolwich 
 and Eeading beds and the London clay, the Bracklesham 
 and Bagshot sands, and the higher fresh-water beds of 
 the Eocene series. 
 
 The whole pass under the Solent, as shown in the 
 lower dotted lines ef e', fig. 12, and rise again on the 
 mainland in Hampshire, a considerable portion of which 
 is entirely composed of various sub-divisions of the 
 Eocene rocks. 
 
 Now these disturbed strata were originally deposited 
 horizontally, and after disturbance the Chalk c once 
 spread over an extensive area of Lower greensand, &c. g, 
 to the south, and the Eocene rocks e once spread over 
 the Cretaceous rocks in a curve, at a great height, as 
 shown in the dotted lines e e. Here then in our 
 Secondary and Tertiary rocks you get evidence of the 
 same kind of disturbance and denudation, of which we 
 have such striking proofs when we consider the struc- 
 ture of the country in the western and north-western 
 area, which are composed of Palaeozoic rocks. But in 
 the central part of England the Secondary and Tertiary 
 strata, not having been so much disturbed, have neces- 
 sarily not been much denuded in height, but chiefly 
 backwards from west to east. 
 
 I have still, however, a few words to add respecting 
 the denudation of the Eocene strata. Some of these 
 
of Eocene Strata. 87 
 
 beds in the Woolwich and Eeading and in the Bagshot 
 series consist of sands, portions of which become ex- 
 ceedingly hard, especially when exposed to the air. 
 I have already said that these formations, together 
 with the Chalk, once spread much further to the west 
 than they do now, because outlying patches of Eocene 
 rocks occur here and there almost at the very edge of 
 the great Chalk escarpment, as shown in figure 7. The 
 original continuation of both in a westward direction 
 is shown in the dotted lines in the same diagram. 
 
 Now it so happened that when the wasting process 
 took place that wore away both these formations from 
 west to east, the softer clays and part of the sands of 
 the Eocene strata were more easily removed than 
 certain much harder portions of the sands, and the 
 result is that over large areas, such as Marlborough 
 Downs, great tracts of chalk are strewn with huge blocks 
 
 Fig. 13. 
 
 of tabular sandstone lying so close together, that some- 
 times over miles of country you may almost leap from 
 block to block without touching the chalk on which 
 they lie. In the above figure No. 1 represents the 
 Chalk, and 2 the overlying Eocene clays and sands ; and 
 the isolated blocks lying directly on the topmost beds 
 
88 Denudation of Eocene Strata. 
 
 of the chalk represent the thickly scattered masses of 
 stone left on the ground after the removal by denu- 
 dation of other and softer- parts of the Eocene strata 
 No. 2. Frequently they are found scattered even on 
 the terraces of the Lower Chalk, a remarkable ex- 
 ample of which occurs at the old British town of 
 Avebury, near which the lower terrace of Chalk (as in 
 the diagram) is strewn with 'grey wethers,' as they 
 are termed, and immense masses set on end by a 
 vanished people stand in the ancient enclosure. Some- 
 times even on the plains of Grault or Kimeridge clay 
 well out to the north or west of the escarpment, as 
 for instance at Swindon, blocks angular or half-rounded 
 lie in the meadows, marking the immense waste to 
 which the whole territory has been subjected long 
 after the close of Eocene times. Besides the name of 
 ' grey wethers,' they are known by the name of Sarsen 
 stones, and Druid stones, and all the standing masses 
 of Avebury and Stonehenge, popularly and probably 
 erroneously supposed to be Druidical temples, have 
 been left by denudation not far from the spots where 
 they have since been erected into such grand old monu- 
 ments by an ancient race.* 
 
 I think I have now stated enough to enable you to 
 
 * The smaller stones at Stonehenge have been brought from a dis- 
 tance. They are mostly of igneous origin, and are believed by Mr. Fer- 
 gusson to have been votive offerings. 
 
Mountains and 'Table-Lands. 89 
 
 form a general idea of the geological phenomena which 
 produce the leading features of the scenery of England. 
 I might add many details respecting other portions of 
 England, such as the relation of the Secondary rocks to 
 the older rocks of Devon, the structure of the Malvern 
 range and of the Mendip Hills, or of the beautiful Vale of 
 Clwyd, in North Wales, consisting of a bay of soft New 
 red sandstone, bounded by Silurian mountains and old 
 limestone cliffs, and of the still larger Vale of Eden, in 
 the North, where the mountains of Cumberland look 
 down on an undulating ground of Permian and New 
 red strata. But it would not add much to the general 
 knowledge which I wish to impress on you, viz. that 
 England is mountainous in the west, or in Devon, 
 Wales, and Cumberland, because of disturbance and 
 great denudations ; and that it consists of plains and 
 table-lands in the central and eastern parts because 
 the strata there are flat and softer, and because they 
 have been denuded in such a manner that their western 
 portions have been chiefly cut away and thus their 
 edges form long escarpments. 
 
 In the next lecture I shall have something to say 
 about the softer coverings of this hard skeleton. 
 
9 
 
 LECTURE IV. 
 
 THE MIOCENE AND PLIOCENE TERTIARY STRATA. GLACIAL 
 PHENOMENA ; AND ORIGIN OF CERTAIN LAKES. 
 
 WE now come to the Middle and Upper Tertiary strata, 
 the first of which consists of the Miocene beds. Their 
 position is shown on the geological scale at page 20, 
 above the upper Eocene formations. They, however, 
 play such a very unimportant part in the physical 
 geology of the mass of our country, that I shall dismiss 
 them in a very few words. 
 
 The Miocene beds are only known in Britain in the 
 island of Mull, one of the Western islands of Scotland, 
 where there are certain strata of shale, interstratified 
 with beds of basalt and volcanic ash, first described 
 by the Duke of Argyll, and known to be of Miocene 
 date, because of the plants which occur in them being 
 all distinct from any living species, and many the 
 same as those well-known to be of Miocene age, in 
 
Miocene Beds. 91 
 
 Bohemia, on the banks of the Khine, in Switzerland, 
 and in other places where Miocene formations are well 
 developed. 
 
 In the south-west of England, in the neighbourhood 
 of Dartmoor, at a place called Bovey Tracey, in a flat 
 area ten miles long by two miles wide, there are also 
 found beds of Miocene clay interstratified with bands 
 of imperfect lignite ; and of late these beds, the age of 
 which was for long a puzzle, have been investigated 
 through the liberality of Miss Burdett Coutts, who 
 paid all the expenses to enable a gentleman in that 
 neighbourhood to examine the nature of these strata 
 because there were no commercial works there of 
 sufficient importance to develop them ; and it required 
 digging in order to enable any one to arrive at just 
 conclusions as to the nature of the strata. The result 
 was, from an examination of the fossil plants by Pro- 
 fessor Heer of Zurich, that they were also found to be 
 of Miocene date ; and it is an important fact, that 
 similar plants are not only found here and there in 
 Scotland, Ireland, and England, in Bohemia, and on 
 the Ehine, but many of them also occur in Iceland, 
 and in North America and Greenland beyond the Arctic 
 circle. The meaning of this is not yet understood^ 
 for many of the plants are of a nature that seem to 
 bespeak a warmer climate than that of the British 
 Islands at the present day, and it is besides difficult to 
 
92 Crag. 
 
 see how such plants could grow in Arctic regions, where 
 the stimulus of light is wanting during half the year. 
 This is one of those things which we cannot explain, and 
 about which we are waiting for light. 
 
 Above the Miocene beds come the Pliocene strata ; 
 that is to say beds still newer in the series, and these in 
 the lower part consist of subdivisions generally known 
 as the Crag (a workman's term). At the base lies the 
 Coralline Crag, and above this lies the Eed Crag, which 
 in some places is not conformable to the Coralline Crag 
 below, showing that an interval marked by denudation 
 elapsed between the deposition of the strata. Much 
 newer than the Eed Crag is the Norwich or Mammali- 
 ferous Crag, differing in many details from either of the 
 others. All of these occupy certain minor patches in 
 Norfolk and Suffolk ; and here and there on the borders 
 of the Weald, in some situations on the very top of the 
 Chalk Downs, there are small patches of sand which are 
 provisionally placed by some geologists on the horizon 
 of part of the Crag. But this is doubtful. The lower, 
 or Coralline Crag, contains 51 per cent, of species of 
 shells still living in the present seas. The Red Crag 
 has a still larger proportion of existing species, showing 
 that it approaches nearer to our own day, not only 
 because it lies above the Coralline Crag, but also 
 because it contains a greater per-centage of living 
 species mixed with the fossil remains ; and along with 
 
Crag. 93 
 
 the shells which form the chief mass of that formation, 
 there are found the bones of a few species of Mammalia, 
 some belonging to the sea, and others to the land. 
 Those of marine origin are cetacean, as the whale; 
 and along with these also occur the remains of the 
 Mastodon, a remarkable kind of Elephant, with teeth 
 which differ very much from that of the true elephant 
 in certain particulars, but these details it is not my 
 object now to explain. Then, in the Mammaliferous 
 crag of newer date, we have a larger proportion of 
 Mammalian remains, hence its name. In it have been 
 found the bones of the Mastodon, also of an extinct 
 Elephant and other large mammalia, and of the ass, 
 the beaver, and a great number of other smaller 
 animals. I mention these things, not because these 
 formations play an important part in British physical 
 geography, as they are generally so far buried under 
 superficial strata of one kind or another that they re- 
 quire to be looked for, and thus do not at all affect the 
 scenery, but to show you the kind of changes in phy- 
 sical geography that our country, in comparatively late 
 times, must have undergone. If it has undergone these 
 changes in late times, far greater are the numbers and 
 the kinds of changes that it must have undergone in 
 periods that went before, of which the records are often 
 entirely lost. 
 
 We are not of necessity to consider Great Britain as 
 
94 Forest Bed. 
 
 having always been an island during and between the 
 periods that I have already described. It is an accident 
 that it is now an island ; and it has been an island or 
 islands probably many times before, and in many 
 shapes ; and when you consider that we have here two 
 epochs of the Crag, both containing remains of great 
 terrestrial animals, you will see that it must have been 
 joined at times to the main-land, for otherwise these 
 great terrestrial animals could not have found their 
 way into our area. When I describe other periods, still 
 later than the Crag, we shall be able to understand 
 a little more definitely the precise kind of changes that 
 our land in latter days has undergone. 
 
 Younger than the Crag there are certain other minor 
 deposits, portions of which are scattered here and there 
 throughout England. One of the most remarkable of 
 these is the s Forest Bed,' lying underneath the glacial 
 drift on the shore at Cromer in Norfolk. This bed 
 has been traced for miles between high and low water 
 mark, and contains numerous erect stumps of Scotch 
 fir, spruce, yew, alder, oak, &c., together with remains 
 of three elephants, E. meridionales, E. antiquus, and 
 E. primigenius (the Mammoth), a rhinoceros, hippopo- 
 tamus, horse, pig, and other mammalia ; and the whole 
 speaks of a past physical geography, at least during 
 part of which, with a mild climate, our country may 
 have been joined to the Continent. 
 
Glacial Epoch. 95 
 
 Later still there are other small formations, important 
 in themselves and definite to those who study fossil re- 
 mains, but like the Cromer beds, as they scarcely affect 
 the features of the country, I shall say nothing about 
 the causes that brought about a patch here and a patch 
 there of gravel or loam, in which we find relics of the 
 hippopotamus, the rhinoceros, and other mammalia. 
 
 But I must now describe a remarkable episode in the 
 latest Tertiary (or, as some authors call them, the Post- 
 Tertiary) times, known as the Glacial epoch, said to be 
 altogether of later date than the Cromer ' Forest Bed,' 
 and certainly of earlier date than some of the patches 
 just alluded to. This formation has left its traces uni- 
 versally over the whole northern half of the northern, 
 and also over a large portion of the southern hemisphere ; 
 and I hope I shall be able to describe the history of that 
 period, as it affects the scenery of Britain, with some- 
 thing like tolerably accurate detail. Before doing so, 
 however, I must lead you into Switzerland, and show 
 you what kind of effect is being produced there by 
 the ice of the present day, and afterwards into Green- 
 land, and show you what takes place there, and then by 
 the knowledge thus gained, I shall be able to bring 
 you back into our own country, and explain what took 
 place here in that icy episode which is so far distant 
 in time, but which, by comparison with the more 
 ancient periods, almost approaches our own day. 
 
9 6 Modern Glaciers 
 
 Now the first thing I have to do, is to describe what 
 a glacier is. In any large and good map of Switzerland 
 you will see certain white patches here and there on the 
 higher mountain ranges of the Alps. The highest 
 mountain in the Alps, Mont Blanc, rises more than 
 fifteen thousand feet above the sea, and there are other 
 mountains in this great chain which approach that 
 height, ranging from 12,000 to 15,000 feet. The 
 mean limit of perpetual snow upon the Alps is 8,500 feet 
 above the level of the sea. Above that line, speaking 
 generally, the country is mostly covered with snow, 
 and in the higher regions it gathers on the mountain 
 slopes and in the larger recesses, and by force of 
 gravity it presses downwards into the main valleys; 
 where, chiefly in consequence of the immense pressure 
 exerted by the weight and movement of this accumu- 
 lated mass, the snow year after year is converted into 
 ice. Without entering on details, it is enough if I 
 now state that this is proved by well-considered obser- 
 vations made by the best observers of the icy pheno- 
 mena of the Alps. Still accumulating, year upon year, 
 by degrees this ice slides down the valleys, and is 
 often protruded in a great tongue far below the limits 
 of perpetual snow ; for some glaciers descend as low as 
 from three to four thousand feet or thereabouts above 
 the level of the sea, whereas the limit of perpetual 
 snow is 8,500 feet. Now I will not enter into all the 
 
of the Alps. 97 
 
 details of the structure of glaciers, because that will 
 not help us in the special investigation we have now 
 in view ; but I will describe to you what are the effects 
 produced by a glacier in the country over which it 
 slides, and various other glacier-phenomena affecting 
 the scenery of the Alps, and therefore affecting the 
 scenery of our own country in past times when glaciers 
 existed here, and still affecting it in the relics they 
 have left. 
 
 A glacier slides more or less rapidly, according to 
 the mass of ice that fills the valley, and also according 
 to the greater or less inclination of the slope, for in 
 this respect it behaves very like a river. If you 
 have a vast body of water like the Mississippi flowing 
 down a broad valley, although the slope of the valley 
 may be very gentle, still the river flows with great 
 rapidity in consequence of the greatness of the body of 
 water ; so if you have a mass of ice, which represents 
 the snow-drainage of a large tract of country, covered 
 with perpetual snow, then the glacier flows with a 
 rapidity proportionate to the mass of ice, and that 
 rate of progress is modified, increased, or diminished, 
 in accordance with the fall and width of the valley, so 
 that when it is steep, the glacier flows comparatively 
 fast, and when the angle at which the valley slopes is 
 small, it flows with comparative slowness. 
 
 All glaciers are traversed by cracks which are termed 
 
9 8 Modern Glaciers. 
 
 crevasses. Now the mountain peaks that rise above 
 the surface of a glacier in some cases are so steep that 
 the snow refuses to lie upon them, even when they 
 may happen to be above the limits of the average line 
 of perpetual snow, so that masses of rock are always 
 being severed by atmospheric disintegration, and 
 falling from the slopes they find a temporary resting 
 place on the surface of the ice at the margin of the 
 glacier, and, as it were, float upon its surface in long 
 and continuous lines ; for the motion of a glacier is 
 so slow, that the quantity of stones that fall upon its 
 surface is sufficiently numerous to keep up a continuous 
 line of blocks, earth and gravel, often of great width. 
 These stones, when two glaciers combine to form one 
 great stream of ice, as in the glacier of the Aar, at a 
 certain point meet and form one grand line running 
 down the centre of the glacier. These are termed 
 moraines, and at length all of this material that has not 
 fallen into crevasses floats on as it were to the end of 
 the glacier, and is shot into the valley at the end of the 
 ice-stream, frequently forming large mounds, known as 
 terminal moraines. 
 
 Beneath every glacier water is constantly flowing, 
 caused by the melting of the ice both below and on 
 the surface of the glacier, and also in some cases to 
 a less degree, by springs that rise in the rocks below 
 the ice. In the various parts of glaciers, where 
 
Modern Glaciers. 99 
 
 crevasses are not numerous, you frequently find large 
 brooks so wide that you cannot leap across them, 
 and you may have to walk half a mile before you find 
 a passage ; but in all the glaciers that I have seen, long 
 before you reach their lower end, all the surface water 
 has found its way to the bottom of the ice. The water 
 therefore that runs from the end of a glacier very often 
 emerges from an ice-cavern as a large ready-made 
 muddy river, which carries away the moraine rubbish 
 that the glacier deposits at its lower end, in some cases 
 almost as fast as it is formed; perhaps I might rather 
 say as slowly as it is formed, because if you go day 
 after day you might see scarcely any difference in 
 the detail of certain moraines, though in time, when; 
 favourably placed to be worked upon by water, stones 
 of moderate size that have been shed from the ice are 
 carried by the river down the valley. In other cases, 
 however, it happens that from various circumstances 
 moraines are preserved from destruction, and form 
 permanent features in the scenery. 
 
 Now I have something special to say about moraine- 
 stones before I describe the glacial phenomena of our. 
 own island. When an immense weight of ice, in some 
 cases thousands of feet in thickness, forming a glacier,, 
 passes over solid rocks, by the pressure of the moving, 
 mass, the rocks in the valley over which the glacier 
 passes become smoothed and polished not flatly, but in 
 
 H 2 
 
TOO Modern Glaciers. 
 
 wavy lines, presenting a largely mammillated surface. 
 Furthermore, the stones of the surface moraines fre- 
 quently fall into crevasses, and the small debris and 
 finely powdered rocks that more or less cover the 
 surface of a glacier are also borne into these crevasses 
 by the water that flows upon the surface ; the conse- 
 quence is that the bottom of a glacier is not simply 
 bare ice, but between the ice and the rock over which 
 it flows, there are blocks of stone imprisoned, and 
 siliceous and feldspathic debris (chiefly worn from the 
 floor itself), which may be likened to emery powder. 
 The result is, that let the rock be ever so hard, it is, in 
 time, polished almost as smooth as a sheet of glass, 
 and this polished surface is scratched and grooved by the 
 coarser debris that, being imprisoned between the ice and 
 the rocky floor, is pressed along in the direction of the 
 flow of the ice. By degrees, grooves and deep furrows 
 are thus cut in the rock over which the ice passes. 
 
 But the stones that are imprisoned between the ice 
 and the rocky floor not only groove that floor itself, 
 but in turn become scratched by the harder asperities 
 of the rocks over which they are forced; and thus it 
 happens that many of the stones of moraines are 
 covered with straight scratches, often crossing each 
 other irregularly, so that we are able by this means to 
 tell, independently of the forms of the heaps, whether 
 such and such a mass is a moraine or not. 
 
Modern Glaciers. 101 
 
 These indications of the rounding, smoothing, scratch- 
 ing and grooving of the rocks in lines coincident with 
 the flow of the glacier, together with old moraine heaps 
 and scratched stones, are so characteristic of all glaciers, 
 that by this means we are able to detect the important 
 fact that the Swiss glaciers were once of far larger 
 dimensions than they are now, and that they have 
 gradually retreated to their present limits. Far below 
 the present ends of the Swiss glaciers, 50 or 80 miles 
 farther down the valleys, we find all the signs I have 
 described, and others besides, frequently as marked as 
 if the glacier had only left the rocks before the ex- 
 isting vegetation began to grow upon their surfaces. 
 
 Such being the case in Switzerland, where we have 
 been able to study the action of glaciers in detail, we 
 have next to enquire, is there anything further to learn 
 in regions where glaciers are on a far greater scale? 
 Those who have read the descriptions of navigators 
 will be aware that in Greenland, the average ice-line, 
 as a whole, descends lower and lower as you go north- 
 ward, till in the extreme north the whole country is 
 one universal glacier. The same universal covering of 
 ice is found in that southern land, discovered by Eoss, 
 and known as Victoria Land, where the mountains rise 
 some of them ten, twelve, and fourteen thousand feet 
 above the sea, and except here and there, where the 
 cliffs are very steep, the country is covered with a 
 
IO2 Modern Glaciers. 
 
 coating of thick ice. In ^Greenland, where the coast 
 happens to be high and steep, the glaciers break off at 
 the top of the cliffs and fall in shivered icebergs into 
 the sea, but when valleys fairly open into the sea then 
 it frequently happens that prodigious glaciers push 
 their way across the land out to sea, and are in certain 
 cases 12 or 14 miles across at their ends. In the 
 extreme north the glacier has been described as pro- 
 ceeding out to sea, and forming a continuous cliff of 
 ice as far as the eye can reach, far outside the true 
 rocky coast. Some of these vast glaciers have been 
 estimated as being at the very least 3,000 feet in 
 thickness ; and great masses of ice breaking away from 
 their ends, form icebergs, which frequently laden with 
 moraine rubbish, just like that which covers the glaciers 
 of Switzerland, float out into the Greenland seas, 
 and are carried south by a current, along the coast of 
 North America. Some of these bergs are known to 
 float south beyond the parallel of New York, and 
 they have even been seen off the Azores. Melting by 
 degrees as they come into warmer climates the stony 
 freight is scattered abroad, here and there over the 
 bottom of the Atlantic, which thus becomes strewn 
 with erratic blocks, and other debris borne from far 
 northern regions. 
 
 I shall now apply these remarks in our own island, 
 and having ascertained what are the signs by which a 
 
Old British Glaciers. 103 
 
 glacier may be known, I shall show that a large part 
 of the British islands has been subjected to glaciation, 
 or the action of ice. 
 
 Those who know the mountains of the Highlands of 
 Scotland remember that though the weather has had 
 a powerful influence upon them, rendering them in 
 places rugged, jagged, and cliffy, yet, notwithstanding 
 this, their general outlines are often remarkably rounded, 
 flowing in greater and smaller mammillated curves ; 
 and when you examine the valleys in detail you also 
 find that in their bottoms and on the sides of the 
 hills, the same mammillated structure frequently pre- 
 vails. These rounded forms are known to those who 
 specially devote themselves to the study of glaciers by 
 the name of roches moutonnees, a name now in general 
 use in England, because it happened that in Switzer- 
 land glaciers were first described by authors who wrote 
 in French. Ice rounded rocks are exceedingly com- 
 mon in many British valleys, and not only so but 
 the very same kind of grooving and striation, so emi- 
 nently characteristic of the rocks in the Swiss valleys, 
 also marks those in the Highlands of Scotland, Cum- 
 berland, Wales, and other districts in the British 
 islands. Considering all these things, geologists, led 
 twenty-three years ago by Agassiz, have by degrees 
 almost universally come to the conclusion that a very 
 large part of our island was, during ( the glacial period/ 
 
IO4 Continental Ice. 
 
 covered, or nearly covered, with a coating of thick ice, 
 in the same way that the north of Greenland is at 
 present ; so that by the long-continued grinding power 
 of a great glacier or set of glaciers nearly universal 
 over the northern half of our country and the high 
 ground of Wales, the whole surface became moulded 
 by ice ; and the relics of this action still remain strongly 
 impressed on the country, to attest its former power. 
 
 It might be unsafe to form this conclusion merely by 
 an examination of such a small tract of country as the 
 British islands, but when we consider the great Scan- 
 dinavian chain, and the north of Europe generally, we 
 find that similar phenomena are common over the 
 whole of that area ; and in the North American con- 
 tinent, as far south as latitude 38 or 40, you find, when 
 you remove the soil or the superficial covering of what 
 is called drift, and get at the solid rock beneath, that 
 almost everywhere it is smoothed and polished, and 
 covered with grooves and striations similar to those of 
 which we have experience among the glaciers of the 
 Alps. I do not speak merely by common report in 
 this matter, for I know it from personal observation, 
 both in the Old World and the New. We know of no 
 power on earth, of a natural kind, which produces 
 these indications except ice, and therefore geologists 
 are justified in attributing them, even on this great 
 continental scale, to its action. 
 
Old British Glaciers. 105 
 
 You will presently see that this conclusion is forti- 
 fied by several other circumstances. Thus, in the Alps, 
 there is evidence that the present glaciers were once on 
 an immensely larger scale than at present. The proof 
 as usual lies in the polished and grooved rocks far 
 removed from the actual glaciers of the present day, 
 and in numerous moraines on a scale so immense that 
 the largest forming in the Alps in our time are of mere 
 pigmy size when compared with them. The same kind 
 of phenomena occur in the Himalayah, the Andes, 
 and in almost every northern mountain chain or cluster, 
 great or small, that has been examined critically, and 
 therefore there can be no doubt that at a late period of 
 the world's history an extremely cold climate prevailed 
 over much larger tracts of the earth's surface than at 
 present, produced by some cause about which there are 
 many vague guesses, but which no one has yet ex- 
 plained. 
 
 It was at this period that a great part of what is now 
 the British islands was covered with ice. I do not say 
 that they were islands at that time, and I think they were 
 not islands, but probably united with the Continent, and 
 the average level of the land may then have been much 
 higher than at present, chiefly by elevation of the 
 whole and partly because it had not suffered so much 
 degradation ; but whether this was so or not, the moun- 
 tains and much of the lowlands were covered with a 
 
106 Old British Glaciers. 
 
 universal coating of ice, probably as thick as that in the 
 north of Greenland in the present day. While this 
 large ice-action was going on, a slow submersion of the 
 land took place ; and as it sank the glaciers, descend- 
 ing to the level of the sea, deposited their moraine 
 rubbish there. Gradually the land sunk more and 
 more, the cold still continuing, till this country, pre- 
 viously united to the continent of Europe, became a 
 group of icy islands, still covered with snow and small 
 glaciers, which descended to the sea, and broke off in 
 icebergs. These floating south deposited their stony 
 freights as they melted. The proof of this is to be 
 found in the detritus which covers so much of Scot- 
 land and two-thirds of England, composed of clay and 
 gravels mixed with stones and great boulders, many 
 of which are scratched, grooved and striated, in the 
 manner of which we have every-day experience in the 
 glaciers of Switzerland, Norway, and Greenland. 
 
 Much of this clay is known as the * Till ' in Scotland ; 
 and it was only by very slow degrees that geologists 
 became reconciled to the idea that this Till is nothing 
 but moraine rubbish on a vast scale, formed by those 
 old glaciers that once covered the northern part of 
 our country. In fact, Agassiz who held these views, 
 and Buckland who followed him, were something like 
 twenty years before their time ; and men sought to 
 explain the phenomena of this universal glaciation by 
 
Submersion of the Land. 107 
 
 every method but the true one. Mr. Kobert Chambers 
 was, I think, the first after Agassiz, who asserted that 
 Scotland had been nearly covered by glacier ice, and 
 now the subject is being worked out in all its details; 
 thus coming back to the old generalised hypothesis of 
 Agassiz, which is now accepted or on the very verge 
 of acceptance by most of the best geologists of Europe 
 and America. 
 
 Besides the proofs drawn from the scattered boulders, 
 we know that the country was descending beneath the 
 sea during this glacial epoch for another reason, that 
 here and there in the heart of the moraine-matter of 
 the Till, there are patches of sand and clay interbedded. 
 The mass indeed is not stratified, because glaciers do 
 not stratify their moraines, but the waves playing upon 
 them, as they were deposited in the sea, here and there 
 arranged portions in a stratified manner; and there 
 occur at rare intervals, in these patches in Scotland,* 
 the remains of sea-shells of species such as now occur 
 in the far north. Here, therefore, we have another 
 proof of that arctic climate which, in old times, came 
 so far south. 
 
 In Wales we find similar evidence, long since described 
 by myself,f of the sea having risen at least 2,300 feet 
 upon the sides of the mountains, for Wales, like Scot- 
 
 * Lately described to me by Mr. Geikie, in the Scotch Till. 
 f See ' The Old Glaciers of North Wales.' Ramsay. 
 
io8 Ice-borne Drift 
 
 land, also became a cluster of islands, round which the 
 drift was deposited, and great blocks of stone were 
 scattered abroad, floated out on icebergs, that broke 
 from an old system of glaciers, and melted in the 
 neighbouring seas. In this stratified material sea-shells 
 were long ago found in Caernarvonshire by Mr. Trimmer 
 and myself, from 1,000 to 1,400 feet above the sea. 
 
 Erratic blocks of granite, gneiss, feldspathic traps, 
 and of other rocks, some of which came from the 
 Highlands of Scotland, some from the Cumberland 
 mountains, some from the Welsh mountains, and some 
 from the farther region of the great Scandinavian chain, 
 were in the same manner spread over the central 
 counties, and the west and east of England, just like 
 those boulder-beds that are now being formed at the 
 bottom of the Atlantic from the icebergs that float south 
 from the shores of Greenland. 
 
 All of these marine boulder-drifts are rudely strati- 
 fied when viewed on a large scale, and the clays are 
 often interbedded with sand and rounded gravel, but 
 it is remarkable that in most of the great beds of clay 
 that form the larger part of the formation, the stones 
 and boulders that stud the mass are scattered confusedly, 
 and frequently stand on end, like the stones in the 
 Moraine-Till of Scotland, and this is the case even 
 when associated with sea-shells, which shells prove 
 the true marine nature of what often looks like a mass 
 
Sea- shells in the Drift. 109 
 
 of heterogeneous rubbish. A great number of these 
 shells occur in a broken state, and from Scotland to 
 Norfolk on the coast cliffs, they may be found plenti- 
 fully enough when carefully looked for. Between 
 Berwick and the Humber, I have seen them in scores of 
 places ; the most plentiful species, as determined for me 
 by Mr. Etheridge, being Cardium edule, Cyprina Islan- 
 dica, Venus, Dentalium entails, Tellina, Leda oblonga, 
 Astarte borealis, and Saxicana rugosa. On the west 
 coast by the Mersey and near Blackpool, they are 
 equally plentiful, and far inland near Congleton and 
 Macclesfield, I observed the same kind of broken shells 
 600 feet above the sea, and I understand that Mr. 
 Prestwich observed them in the same region at a height 
 of fully 1,200 feet. It is remarkable also what a pro- 
 digious number of ice-scratched stones occur in this 
 drift, under such conditions, that the idea is suggested 
 that they were marked not by glaciers, but by the 
 agency of coast ice. As you travel south, you find that 
 the numbers of the kinds of stones increase according 
 to the number of formations you have passed. North 
 of the Magnesia limestone district, the fragments to a 
 great extent consist of Silurian Old red and Carbon- 
 iferous fragments, then these become mixed with pieces 
 of Magnesian limestone, by and by Oolitic fragments 
 are added, and in Holderness, in places half the number 
 of stones are of chalk generally well scratched, and 
 
1 1 o Emergence of the Land. 
 
 often mingled with broken shells. But it is evident 
 that the low chalk hills of Yorkshire are not of a kind 
 to have given birth to glaciers, and therefore the scratch- 
 ing and distribution of the chalk-stones may have been 
 produced by coast ice ; and the same may be said of 
 other low parts of England, both on the coast and 
 inland where the drift prevails, the currents which 
 scattered the ice-borne material having on a great 
 scale flowed approximately from north to south. 
 
 But England, south of the estuaries of the Severn 
 and the Thames, for the most part seems all this time 
 to have remained above the waters, for not only is the 
 country in general destitute of drift, but it is only close 
 on the sea near Selsea and Brighton that erratic boulders 
 of granite &c. have been found, apparently floated from 
 the Channel Islands or from France. 
 
 After a long period of submergence the country 
 gradually rose again, and the evidence of this I will 
 prove chiefly from what I know of North Wales, 
 although I could easily do the same by taking you 
 to the Highlands of Scotland. 
 
 I shall take the Pass of Llanberis as an example, for 
 there we have all the ordinary proofs of the valley 
 having been filled with glacier-ice. First, then, after 
 the great glacial epoch, the country to a great extent 
 sunk below the water, and the drift was deposited, and 
 more or less filled many of the valleys of Wales. When 
 
Decline of the Glaciers. 1 1 1 
 
 the land had risen again to a considerable height, the 
 glaciers increased in size, although they never reached 
 the immense magnitude which they attained at the 
 earlier portion of the icy epoch. Still, they became 
 so large, that such a valley as the Pass of Llanberis 
 was a second time occupied by ice, and the result was, 
 that the glacier ploughed out the drift and loose rub- 
 bish, that more or less covered the valley. Other 
 cases of the same kind could easily be given, while, 
 on the other hand, in many valleys you find the drift 
 still remaining. By degrees, however, as we approach 
 nearer our own days, for unknown reasons, the climate 
 slowly ameliorated, and the glaciers began to decline, 
 till becoming less and less, they crept up and up ; and 
 here and there, as they died away, they left their ter- 
 minal and lateral moraines, still in some cases as well 
 denned as moraines in lands where glaciers now exist. 
 Frequently too, masses of stone, that floated on the 
 surface of the ice, were left perched upon the rounded 
 roches moutonnees, in a manner somewhat puzzling 
 to those who are not geologists ; for they lie in 
 such positions that they clearly cannot have rolled into 
 them from the mountain above, because their resting 
 places are separated from it by a hollow ; and besides 
 many of them stand in positions so precarious, that if 
 they had rolled down from the mountains they must, 
 on reaching the points where they lie, have taken a 
 
ii 2 Glacial Origin of Lakes. 
 
 final bound, and fallen into the valley below. But 
 when experienced in the geology of glaciers, the eye 
 detects the true cause of these phenomena, and you 
 have no hesitation in coming to the conclusion, that as 
 the glacier declined in size, the errant stones were let 
 down upon the surface of the rocks so quietly and so 
 softly, that there they will lie, until an earthquake 
 shakes them down, or until the wasting of the rock on 
 which they rest precipitates them to a lower level. 
 Finally, the climate still ameliorating, the glaciers 
 shrunk farther and^ farther into the heart of the moun- 
 tains, until, at length, here and there in their very 
 uppermost recesses, you find the remains of tiny 
 moraines, marking the last relics of the ice before it 
 disappeared from our country. 
 
 All these things give distinctive characters to our 
 mountains, very different, I believe, from those of moun- 
 tain ranges where glaciers never were. I confess, how- 
 ever, that I have never seen any of the latter, my travels 
 having been confined to Europe north and immediately 
 south of the Alps, and to parts of North America. 
 
 There are certain other points that materially affected 
 the geography of our country, and that is what I 
 believe to be the glacial origin of many of our lakes. 
 
 When glaciers descended into valleys, and deposited 
 their terminal moraines, it has sometimes happened that 
 when a glacier declined in size its moraine still remained 
 
Moraine- dammed Lakes. 113 
 
 tolerably perfect, with this result that the drainage for- 
 merly represented by ice is now represented by running 
 water, which is dammed in between the surrounding 
 slopes of the solid mountain and the mound formed by 
 the terminal moraine, thus making a lake. There are 
 such lakes on the Italian side of the Alps, and there are 
 several among the mountains of Wales. Whether there 
 are any in Cumberland I do not know, but as yet I have 
 seen none in Scotland dammed by the terminal moraines 
 of common valley glaciers, although I have no doubt 
 that they may exist in parts that I have not visited. 
 Furthermore, sometimes on the outer side of these 
 moraines we find stratified boulder-drift, showing that 
 the old glacier descended to the level of the sea and 
 deposited its moraine there, and breaking up, floated 
 about as icebergs bearing boulders. By-and-by the 
 glacier that was produced by the drainage of snow dis- 
 appeared, and is now represented by water, forming a 
 lake dammed by a moraine, outside of which lie long* 
 smooth slopes of stratified drift. 
 
 Such lakes are always on a small scale, but there are 
 others on a larger scale, having a far more important 
 bearing upon the physical geography of our country, 
 and of many other countries in the northern hemi- 
 sphere, and I have no doubt also in the south. The 
 theory which I am going to propound to you is my own, 
 and is not old. It gave rise to a considerable amount 
 
 I 
 
ii4 Glacial Origin of Lakes. 
 
 of opposition, and also to some approval, and I believe 
 that in time it will be sure to make its way. 
 
 There is no point in physical geography more difficult 
 to account for than the origin of most lakes. When 
 thought about at all, it is easy to see that lakes are the 
 result of the formation of hollows, a great proportion 
 of which are true rock-basins, that is to say, hollows 
 entirely surrounded by solid rocks, the waters not being 
 retained by mere loose detritus. But the great diffi- 
 culty is, how were these rock-basins made? In the 
 first place, consider what is the effect of marine denu- 
 dation. On the sea-shore, where the waves are always 
 breaking, the effect of this and of the weathering of 
 cliffs that rise above the waves is to waste back the 
 land. But the sea in this case cannot make a hollow 
 below its own average level. What it does, if there 
 are any hollows there, is to fill them up with detritus, 
 for it cannot cut them out. The consequence is, that 
 the chief power of the sea working against the land 
 and wasting it back, is to act as a great planing 
 machine, wearing off the larger irregularities that rise 
 above its level in the manner shown in the description 
 of the first denudation of the Weald at page 80, and 
 of South Wales at page 1.40. 
 
 Again, what is the effect in any country of running 
 water ? Rivers cannot make hollows that are sur- 
 rounded by rocks on all sides. All that running water 
 
Synclinal Basins. 1 1 5 
 
 can do upon the surface is to scoop out trenches or 
 channels of greater or less width, forming gorges or 
 wider valleys, according to the nature of the rivers 
 and the rocks, and the time employed in the work. If 
 you have an inclined plane, with a long slope, gentle 
 or steep, water will run upon it because of the slope, 
 and, aided by atmospheric disintegration, it will cut out 
 a channel, but it cannot make a basin. 
 
 Again : it may be contended that the hollows were 
 formed by the disturbance of the rocks, so as to throw 
 them into a basin-shaped form. But when we take 
 such lakes as that of Geneva, the Lake of Thun, the 
 lakes of Lucerne, Zurich, Constance, and the great 
 lakes on the Italian side of the Alps, and examine the 
 strata critically, we find that they do not lie in the 
 form of basin-shaped synclinal hollows. Such de- 
 pressions are the rarest things in nature ; that is to say, 
 hollows formed of a number of strata bent upwards at 
 the edges all round into the form of a great dish, the 
 very uppermost bed or beds of which shall be con- 
 tinuous and unbroken underneath the water of the lake. 
 If such basins exist at all, I never saw one, though 
 specially looking out for them in many regions, and 
 I believe that they have been only assumed by those 
 who have not realised the meaning of denudations on 
 a large scale, and therefore are apt to consider hills 
 and valleys as the result, mainly, of disturbance and 
 
 I 2 
 
1 1 6 Glacial Origin of Lakes. 
 
 dislocation. From repeated examinations I feel assured 
 also that the Swiss valleys generally, and the lake-valleys 
 in particular, do not lie in gaping rents or fissures, 
 and, indeed, after half a life spent in mapping rocks, I 
 believe that there is no necessary connection between 
 fractures and the formation of valleys. 
 
 It might, however, be said that these lakes lie in 
 areas of special depression, made by the sinking of the 
 land underneath each lake. Lakes are, however, so 
 numerous in the Alps, and in the Highlands of Scot- 
 land, where they occur by the hundred, and in North 
 America by the thousand, that I feel sure the theory of 
 a particular depression for each lake will not hold. In 
 the northern part of North America it is as if the whole 
 country were sown broadcast with lakes, large and 
 small, and great part of the country not being moun- 
 tainous, but consisting of undulating flats, it becomes 
 an absurdity to suppose that, so close together, a special 
 area of depression was provided for each lake. The 
 physical geology of America and of Scotland entirely 
 goes against such a supposition, and I believe, though 
 the subject is a little less evident, that it is equally 
 untenable for the Alps, and the lowlands between the 
 Alps and the Jura.* Now, when you have come to 
 
 * For details see Quarterly Journal of the Geological Society, 1862, 
 p. 185. There are some lakes and inland seas said to occupy areas of 
 special depression, for I by no means wish you to understand me as 
 asserting that this theory accounts for the probable origin of all lakes. 
 
Denudation by Ice. 117 
 
 these conclusions, you will see that it is difficult to 
 account for the existence of hollows, composed of hard 
 rocks, which completely inclose lakes. 
 
 If, then, we have disposed of these erroneous hypo- 
 theses for the formation o such hollows, what is left ? If 
 the sea cannot do it, nor weather, nor running water, and 
 if the hollows were not formed by synclinal curves of 
 the strata, and if they do not necessarily lie in gaping 
 fissures, nor yet in areas of special depression, the only 
 remaining agent that I know is the denuding power 
 of ice. In the region of the Alps it is a remarkable 
 circumstance that all the larger lakes lie in the 
 courses of the great old glaciers each lake in a true 
 rock-basin. This is important, for though it is clear 
 that the drainage of the mountains must have found its 
 way into these hollows, either in the form of water or 
 of glacier-ice, yet if ice had nothing to do with their 
 formation, we might expect an equal number of lakes 
 great and small in other regions where the rocks are 
 equally disturbed or of like nature, but where there 
 are no traces of glaciers. I have never observed that 
 this is the case, but rather the reverse. 
 
 I will take the Lake of Geneva as a special example 
 before applying the theory to our own country. This lake 
 is about forty miles long, and in its broadest part about 
 
 Many are dammed up by drift, and in other regions some may owe 
 their origin to causes of which I know nothing. 
 
1 1 8 Glacial Origin of Lakes. 
 
 twelve miles wide. It lies at the mouth of the upper 
 valley of the Rhone and directly in the course of the 
 great old glacier, which was something like a hundred 
 miles in length from its source to where at its end 
 it abutted upon the Jura mountains, by 125 miles from 
 south-west to north-east at its lower end. It is known 
 to have been so large by the effects produced on the 
 country over which it flowed, and also by the fact that 
 huge blocks of gneiss, granite, and others from the 
 Alps lie scattered on the flanks of the Jura, associated 
 with moraine matter in such a way as to leave the 
 former existence of that great old glacier beyond a 
 doubt. 
 
 The Lake of Geneva where deepest, near its eastern 
 end, is 984 feet in depth, and it gradually shallows to 
 its outflow. By examining the sides of the mountains 
 on either side of the valley of the Ehone, through 
 which the glacier flowed, we are able to ascertain what 
 was the thickness of the ice in that valley when the 
 glacier attained its greatest size, viz. nearly 2,800 feet 
 above the surface of the lake, or nearly 3,800 if we add 
 the depth of the water.* By similar observations on 
 the Jura, it is clear, that where the ice abutted on 
 that range, it still maintained a thickness of something 
 like 2,200 feet where thickest, swelled as it was by 
 the vast tributary masses of the glacier of the Arve, 
 
 * But probably more. 
 
Scooping Power of Glaciers. 119 
 
 and by others of smaller size that flowed down the 
 valleys that open on the south of the Lake of Geneva. 
 Now, consider the effect of this gigantic glacier flowing 
 over the Miocene rocks, which in this part of Switzer- 
 land are comparatively soft, and yet of unequal hard- 
 ness ! That mass, working on slowly and steadily, for 
 a period of untold duration, must have exerted a pro- 
 digious grinding effect on the rocks below. Where 
 the glacier-ice was thickest, there the grinding power 
 was greatest, and the underlying rock was to a very 
 considerable extent destroyed and worn away; but 
 where at its western end near Geneva the ice was 
 thinner by reason of the melting of the glacier, there 
 the pressure and grinding power were less, and the 
 waste of the underlying rock was proportionately di- 
 minished. The result was, that a great hollow was 
 scooped out, at least 984 feet deep in the deepest part, 
 without allowing for any sediment that may now cover 
 the bottom, this hollow shelving up towards the present 
 margin of the lake. When you think of this, you may 
 at first deem it impossible, but when you compare the 
 depth with the length of the lake and the height and 
 weight of the ice above, and reduce all to a true scale, 
 you will see that in a drawing the depth of the rock- 
 basin is comparatively quite insignificant.* 
 
 * These points were illustrated by diagrams, as were all the other 
 questions raised in this lecture. 
 
I2O American Lakes. 
 
 Therefore I have been forced to the conclusion, from 
 a critical examination of many of the lakes in and 
 around the Alps, that their basins were scooped out by 
 the great glaciers of the icy period; some of which 
 were as thick or thicker than that which descended the 
 valley of the Ehone. 
 
 Now, if we examine the maps of the northern hemi- 
 sphere generally, beginning at the equator, and coming 
 north, it is remarkable that we find very few lakes in 
 its southern regions. As we proceed northwards into 
 America, in latitudes 38 and 40, the lakes begin to 
 increase, and soon become tolerably numerous; and 
 north of New York, towards the St. Lawrence, they 
 become so numerous that they appear to be scattered 
 over the whole country in every direction, and beyond 
 this to the north and west of Lake Superior and the 
 St. Lawrence, the whole country is dotted as thickly as 
 lakes can be put upon the maps, and a vast number of 
 the smaller ones are omitted for want of room. The 
 whole of that country has been completely covered by 
 ice as the researches of geologists show. 
 
 Coming to this side of the Atlantic, and examining 
 the Scandinavian chain on the east, where the slopes 
 are less than on the western flank, all round the Gulf 
 of Finland, and the Baltic, the whole country is covered 
 with lakes, many of which, I am informed, lie in true 
 rock-basins, while in Finland, according to Professor 
 
British Lakes. 121 
 
 Nordenskiold, they are in a glaciated country chiefly 
 dammed in by heaps of detrital matter called Osars.* Go 
 into North Wales, where glaciers were common in every 
 large valley : there we have the lakes of Llanberis, of 
 Cwellyn, Ogwen, Llyn-y-Ddinas, Llyn-Grwynant, Llyn- 
 llydaw, and all the minor tarns in the upper Corries. 
 There are many celebrated lakes in parts of Ireland 
 and Cumberland both eminently glaciated countries 
 and others unknown to fame besides. Gro from the 
 comparatively southern parts of our island, and examine 
 Scotland ; in Sutherland, and the Lewes, and in other 
 Western islands ; in Inverness-shire, Perthshire, Dum- 
 bartonshire, and the Mull of Cantyre, the whole country 
 is sown with lakes a vast number of which I can 
 testify lie in true rock-basins, though some may merely 
 lie in hollows made by unequal accumulation of glacier 
 drifts, or among the bending gravelly mounds of the 
 ' Kaims.' And all that country, like Greenland now, 
 was in the icy period ground by a heavy weight of 
 slowly moving and long enduring glacier-ice, which ice 
 I firmly believe was the scooping power that originated 
 most of the lake scenery of our country. I go further, 
 
 * The Eskirs of Ireland and the Kaims of Scotland. These are 
 common in the great valley of the Frith of Clyde, especially near 
 Lanark and Carstairs, where they form vast elongated irregular mounds 
 of gravel above the true glacial detritus. They inclose lakes and peat- 
 mosses, once lakes. They have been mapped and described by Mr. 
 Geikie. They also occur in Northumberland. 
 
122 Progress of 
 
 for I have shown that in rocky regions, the farther 
 north you go, the more do lakes increase in number, 
 and I am convinced that this fact is not a mere acci- 
 dental coincidence, but is one of the strongest proofs 
 of the former existence of that wide-spread coating of 
 glacier-ice, that in old times moulded the face of so 
 much of the northern hemisphere. 
 
 This theory, brought out in March, and published in 
 August 1862, of the glacial origin of so many lakes in 
 the northern hemisphere, or rather wherever there have 
 been either continental or mountain glaciers, was on 
 the whole received with disfavour or ' faint praise ' in 
 England when first produced, and it fared no better in 
 Switzerland, and but little better in the north of Italy, 
 where however it was allowed that it ( deserved the 
 gravest attention.' Nevertheless, it begins to make 
 way among some of those physical geologists whose 
 opinions I highly value. Mr. Greikie in his * Phenomena 
 of the Grlacial Drift of Scotland,' has declared that it 
 will be 'at last accepted as the true theory of the 
 origin of those rock-basins of the Alps and of the 
 northern hemisphere generally that are occupied by 
 lakes.' Sir William Logan, in his report on the geology 
 of Canada for 1863, has drawn attention to it in a foot- 
 note, and in the text he says, that the great North 
 American lake-basins ' are depressions not of geological 
 structure but of denudation ; and the grooves on the 
 
the Theory. 123 
 
 surfaces of the rocks which descend under their waters, 
 appear to point to glacial action as one of the great 
 causes which have produced these depressions.' Dr. 
 J. S. Newberry, in the American ' Annual of Scientific 
 Discovery ' for 1863, pp. 252 and 255, has also drawn 
 special attention to the subject ; and Dr. Otto Torre], 
 who has given so much attention to the glacial geology 
 of Greenland, Spitzbergen, and Scandinavia, informed 
 me that my theory threw an unexpected light on the 
 Swedish lakes.* 
 
 * Since the text was printed, Professor H. Y. Hind of Toronto has ' 
 informed me that in 1855-6 he read a paper before the Canadian Insti- 
 tute of Toronto, ' On the Origin of the Basins of the great American 
 Lakes,' in which he attributed that origin to ice, but the memoir was 
 never printed. He has also pointed out to me the following passage in 
 his work on the ' Canadian Ked River, and Assinniboine, and Saskat- 
 chewan Expeditions,' published in 1860 : ' The wide-spread phenomena 
 exhibiting the greater or less action of ice, such as grooved, polished, 
 and embossed rocks, the excavation of the deep lakes of the St. Lawrence 
 basin, the forced arrangement of drift, the ploughing up of large areas, 
 and the extraordinary amount of the denudation at different levels 
 without the evidence of beaches, all point to the action of glacial 
 ice previous to the operations of floating ice in the grand pheno- 
 mena of the drift,' 
 
I2 4 
 
 LECTURE V. 
 
 NEWER PLIOCENE EPOCH, CONTINUED. BONE-CAVES. 
 DENUDATION OF THE COASTS OF BRITAIN. BRITISH 
 CLIMATES AND THEIR CAUSES; AREAS OF DRAINAGE, 
 RIVER VALLEYS, AND THEIR ORIGIN ; OLD RIVER GRA- 
 VELS, AND PRE-HISTORIC HUMAN REMAINS. HISTORICAL 
 ELEVATION OF THE COUNTRY. 
 
 I HAVE already said that during the younger Tertiary 
 epochs, England has been repeatedly joined to the 
 main-land, a circumstance proved by the remains of 
 terrestial mammalia, the bones of which are found im- 
 bedded in the strata. Thus, to take one late instance, 
 it is clear that England must have been united to the 
 Continent before the formation of the Mammaliferous 
 Crag (one of the Newer Pliocene deposits), because we 
 find in these beds the remains of a number of terrestrial 
 quadrupeds, many of them of great size. Later still, at 
 Cromer, in Norfolk, there is a bed known as ( the 
 forest-bed? because there are a number of trees im- 
 
Britain joined to the Continent. 125 
 
 bedded in it. In this 'forest-bed' are found the 
 bones of the Rhinoceros Etruscus, the ElepTias meri- 
 dionalis, and the great Mammoth, known to naturalists 
 as the ElepTias primigenius according to Dr. Falconer 
 the oldest strata in which this elephant has yet been 
 found. Such large mammalia, on any hypothesis, did 
 not all originate in a small detached island like England, 
 but formed parts of large families of Pachydermata 
 that inhabited the north of Europe, America, and Asia 
 at various periods of geological time, and they could 
 only have passed into our area by the union of England 
 with the Continent. 
 
 Again, in the south of England, at Selsey Bill, there 
 are post-pliocene strata on the sea-shore described by 
 Mr. Godwin-Austen, one of the beds containing species 
 of living marine shells, not belonging to icy seas, and 
 overlaid by icy boulder-drift, and in the former there 
 were found the remains of another well-known species 
 of elephant, the E. antiquus, lying on clay on which 
 stumps of trees, the remains of an old wood, still 
 stand. 
 
 These boulder-drifts were formed during a period of 
 cold, accompanied by a vast extension of the great 
 glaciers that covered so much of the north of Europe 
 and America, as I have already explained. While 
 the boulder-drift was forming, the country slowly sunk, 
 in our country so far that the mountains of Wales, 
 
126 Severance and Reunion. 
 
 Cumberland, the higher parts of Derbyshire and of 
 Scotland, became merely groups of small islands. But 
 the cold continued so intense, even during that period of 
 submergence, that these islands were surrounded by ice, 
 and more or less covered by perpetual snow. Then, of 
 course, our country was entirely severed from the main- 
 land ; but after this period it was again elevated, and 
 there is evidence that it was again united to the Con- 
 tinent, for we now find the remains of a number of new 
 species of animals unknown in the older sub-formations. 
 The Mammoths which lived before this time must have 
 been driven out of our area by that submergence, 
 unless it be possible that a few, with other mammalia, 
 managed to live on in the extreme south of what is 
 now England, which apparently only suffered a very 
 small change of level. Farther north such large animals 
 could not have lived on mere groups of icy islands, on 
 which, if there was any vegetation, it was exceedingly 
 scanty. Such animals required a large amount of 
 vegetation to feed them, and it is therefore clear that 
 they must have died out or been banished from our 
 area by that submergence. We find, however, that 
 on the re-elevation of the country, it must have been 
 re-united to the Continent, because this great hairy 
 Elephant again appears, and is associated with a number 
 of other animals that also migrated from the Continent 
 of Europe to our area. Among these there is the 
 
Bone-Caves. 127 
 
 Rhinoceros tichorhinus, and various oxen, one of which, 
 the Auroch, is still living in the forests of Lithuania. 
 We have also, in the old lake and river-beds of that 
 period, Hippopotami, Horses, the great Deer known as 
 the Cervus megaceros, commonly called the Irish Elk; 
 the Reindeer ; the wild Ass ; a large Bear known as 
 the Ursus spelceus ; a great Tiger ; the Leopard ; the 
 Lynx ; the wild Cat of the existing species ; the Hyaena 
 spelcea, an extinct species, along with wolves, foxes, 
 otters, beavers, and a number of other small animals. 
 Besides these, found in alluvial, gravelly, and old lake 
 deposits, their remains are also found in the bone- 
 caves of the country. These bone-caves are often of 
 very old date, and always occur in limestone strata, in 
 which they have been formed in consequence of part 
 of the lime being dissolved. Most of the solid lime- 
 stone rocks are exceediogly jointed, and rain-water 
 finding its way down and in among the strata through 
 the joints, the carbonic acid in the water by degrees 
 dissolves part of the limestone in the form of bicar- 
 bonate of lime, and running in underground channels 
 sometimes as large rivers, caves have been formed often 
 of great extent, and branching in many directions, and 
 in these caves the remains of extinct mammals are 
 found mingled with the bones of species that still in- 
 habit our country and the Continent of Europe. Some- 
 times they seem to have been washed in through the 
 
128 Bone-Caves. 
 
 mouths of the caverns, sometimes they fell or were 
 washed in through openings in the roof; and not un-- 
 frequently the detached bones of animals, or the 
 animals themselves, have been dragged in by beasts 
 of prey, such as the old Hyena that inhabited these 
 caves. One evidence of this is, that the bones are 
 frequently gnawed, for very commonly you may detect 
 on them the marks of the teeth of carnivora. Another 
 proof of these caves having been inhabited (as shown 
 by Dr. Buckland) is, that the sides of the caverns 
 themselves are occasionally smooth, having been polished 
 by the animals rubbing against the rock as they passed 
 by corners and along other uneven surfaces in their 
 way in and out of the recesses of their dens. 
 
 There is no doubt that many of these caves date 
 from before the epoch of the icy drift, and also that 
 the bones of animals found their way into some of 
 them before that period ; and since it closed, many of 
 them have been more or less tenanted as caverns down 
 to the present day, or bones have been at intervals 
 washed into them, and thus it happens that organic 
 remains perhaps of older date than the drift are found in 
 the same cave with bones belonging to the icy period, 
 and to minor epochs of still later date. Mingled with 
 the bones of extinct species in various parts of England 
 and Wales, flint implements and other remains of man 
 have been found, and though it is usually said that 
 
Plains of Boulder-Drift. 1 29 
 
 they are always of later date than the boulder-beds, 
 it is by no means certainly proved that this is the case. 
 Some of the Devonshire caves in which the works of 
 man were found were above water during the drift 
 period, and others farther north, like that of Cefn in 
 North Wales, were below the sea, for the boulder beds 
 reach a higher level ; and along with Dr-. Falconer I 
 found fragments of marine shells of the drift, in the 
 cave overlying the detritus that held the bones. No 
 human remains were found in that cavern, and it is just 
 possible that some of those in the south of England 
 may have been above water and inhabited, while others 
 farther north lay underneath the icy sea. 
 
 After the elevation of the country that succeeded 
 the drift period, the probabilities are that England was 
 united to the Continent, not by a mass of solid rock 
 above the sea level, but by a continuation of the 
 boulder-drift over what is now the Grerman ocean ; and 
 across this plain many of the animals of which I have 
 spoken migrated into our area, some of them for the 
 second time. It is the belief of some geologists that at 
 the same period Ireland was united to England and 
 Scotland by a similar plain across the area now covered 
 by the Irish sea, and over this the Megaceros Hiber- 
 nicus, formerly called the Irish Elk, and a number of 
 other animals migrated. The proof is equally clear 
 that Ireland during the drift period, like England, was 
 
ijo Union of England with the Continent. 
 
 in great part submerged, so as to form a group of small 
 islands, and therefore to allow of the country being re- 
 inhabited by large mammals, there must have been 
 ground over which these mammals walked into the 
 Irish area, after the re-elevation of the country. 
 
 An excellent surmise was offered us on this subject 
 by the late Professor Edward Forbes, who drew at- 
 tention to some remarkable observations made by the 
 late Mr. Thompson of Belfast, with regard to the com- 
 parative number of reptiles that are found in Belgium, 
 in England, and in Ireland. In Belgium there are in 
 all 22 species of serpents, frogs, toads, lizards, and the 
 like. In England the number of species is only 11, 
 and in Ireland 5, and the inference that Professor 
 Forbes drew was, that these reptiles migrated from 
 east to west, across the old land that joined our island 
 to the Continent, before the denudations took place 
 that disunited them. Before the breaking up of that 
 land a certain number of them had got as far as 
 England, and a smaller number as far as Ireland, and 
 the continuity of the land being broken up, their 
 further progress was stopped. 
 
 These denudations, of course, did not cease with 
 the breaking up of the land that joined our territory 
 to the Continent, and there are clear proofs of several 
 oscillations of the relative levels of sea and land since 
 that period. This waste of territory is indeed going 
 
Waste of Sea Coasts. 131 
 
 on still, and will always go on while a fragment of 
 Britain remains. Before proceeding further, I would 
 advance one or two proofs, to show you how steady the 
 waste of our country is, that you may know what I 
 have said to be founded on observation. 
 
 Along the east coast of England, between Flam- 
 borough Head and Kilnsea, the strata are composed of 
 what I have called drift or boulder-clay, sometimes 
 of great thickness, and forming well-marked sea-cliffs. 
 This district is called Holderness, and many towns, 
 built upon the coast, have been forced by degrees to 
 migrate landwards, because of the encroachment of the 
 sea. ' The materials,' says Professor Phillips, c which fall 
 from the wasting cliff,' (a distance of 36 miles) ' are 
 sorted by the tide, the whole shore is in motion, every 
 cliff is hastening to its fall, the parishes are contracted, 
 the churches wasted away.' The whole area on which 
 Ravenspur stood, once an important town in York- 
 shire, where Bolingbroke, afterwards Henry IV., landed 
 in 1399, is now fairly out at sea. The same may be 
 said of many another town and farmstead, and the 
 sea is ever muddy with the wasting of the unsolid land. 
 In like manner, all the soft coast cliffs, from the Hum- 
 ber to the mouth of the Thames, are suffering similar 
 destruction, in places at an average rate of from 2 to 4 
 yards a year. One notable example is found at Eccles- 
 by-the-sea in Norfolk. The town at a comparatively 
 
 K 2 
 
1 32 Waste of Sea Coasts. 
 
 late period extended beyond the church tower, which 
 is now buried in blown sand, and the church itself has 
 been destroyed. 
 
 On the south side of the estuary of the Thames, 
 stands the ruined church of the Eeculvers on a low 
 hill of Thanet sand, half surrounded on the land side 
 by the relics of a Koman wall that in old times en- 
 circled the little town. The church has been aban- 
 doned, but is preserved as a landmark by the Admiralty, 
 and groins have been run out across the beach to pre- 
 vent the further waste of the cliff by the sea. As it 
 is, all the seaward side of the Roman wall has long 
 been destroyed, the waves have invaded the hill, and 
 half the church-yard is gone, while from the cliff the 
 bones of men protrude, and here and there lie upon 
 the beach. A little nearer Herne Bay the same marine 
 denudation sparingly strews the beach with yet older 
 remains of man, in the shape of flint weapons of a 
 most ancient type, washed from the gravels that crown 
 part of the cliff. In the Isle of Sheppey, great slips 
 are of frequent occurrence from the high cliff of London 
 clay that overlooks the sea.* 
 
 Again, in the Tertiary basin on the south coast of 
 England, if you walk along the foot-paths that are used 
 
 \ 
 
 * Two acres of wheat and potatoes have in this manner slipped sea- 
 ward in 1863. When I saw them the crops were still standing on the 
 shattered ground below the edge of the cliff. 
 
Waste of Sea Coasts. 
 
 by the coast-guardsmen, you often find that the path 
 on the edge of the cliff comes suddenly to an end, and 
 has been re-made inland. This is due to the fact, 
 that the cliffs, chiefly composed of clay and sands, 
 are so soft, that, as in Sheppey and Holderness, every 
 year large masses of country slip out seaward and are 
 rapidly washed away. 
 
 The waste of this southern part of England and of 
 Holderness, has been estimated at the rate of from 
 two to three yards every year. You will easily see, 
 therefore, that in the course of time, a great area 
 of country must have been destroyed. At Selsey Bill, 
 there is a farmhouse standing about 200 yards from 
 the shore, and the farmer told me, that since he first 
 settled there, as much land has been wasted away 
 as that which now lies between his house and the sea ; 
 and the site of the Saxon Cathedral Church that pre- 
 ceded that of Chichester, is said to be far out at sea. 
 But this waste is not confined to the softer kinds of 
 strata, for further west in Dorsetshire, where Oolites 
 and Chalk form the cliffs, we find the same kind of 
 destruction going on, one remarkable case of which is 
 the great land-slip in the neighbourhood of Axmouth, 
 which took place in the year 1839. The strata there 
 consist on the surface of chalk, underlaid by greensand, 
 which is underlaid by the Lias clay. The chalk is 
 easily penetrated by water, and so is the sand that 
 
1 34 Waste of Sea Coasts. 
 
 underlies it. After heavy rains the water sinking through 
 the porous beds, the clay beneath became exceed- 
 ingly slippery, and thus it happened that the strata 
 dipping seaward at a low angle, a vast mass of chalk 
 nearly a mile in length slipped out seaward, forming a 
 grand ruin, the features of which are still constantly 
 changing, by the further foundering of the chalk and 
 greensand. The waves beating upon the foundering 
 masses destroy them day by day, and in time they will 
 entirely disappear. If you walk along that coast and 
 criticise it with a geological eye, you will observe that 
 a great number of similar land-slips have taken place 
 in times past, of which we have no special record. 
 
 In parts of our country further west, the Silurian 
 rocks, Old red sandstone and Coal-measures on the 
 coast, show evidence of waste ; as for instance at St. 
 Bride's Bay in Pembrokeshire, where the north and 
 south headlands are formed of hard igneous rocks that 
 stand boldly out seaward ; while between these points 
 there are softer Coal-measure strata, which undoubtedly 
 once filled what is now the bay and probably with the 
 other strata spread far beyond. But because of their 
 comparative softness they have been less able than the 
 igneous rocks of the headlands to stand the wear and 
 tear of the atmosphere and the sea waves, and thus 
 they have been worn back, and a large bay is the 
 result. Indeed, all along the west coast where solid 
 
The Gulf Stream. 135 
 
 rocks prevail, hard rocks usually form the promontories, 
 while the bays have been scooped in softer material ; 
 and this, though the rate of waste may not be detected 
 in many years, yet proves its nature. The very exis- 
 tence of sea cliffs proves marine denudation. I merely 
 mention these things to show that denudations on a 
 great scale are going on now, and therefore when I 
 speak of former unions and separations of our island 
 with the main land by denudation, and oscillation of 
 level, the statement is founded on excellent data. 
 
 I now come to other phenomena connected with 
 the physical structure of our island, and its geo- 
 graphy generally ; and first, with regard to the rain 
 that falls upon its surface. If you examine the best 
 hydrographic map of the Atlantic, you will see numer- 
 ous lines and arrows showing the direction of the flow of 
 the ocean currents as drawn by Captain Maury. One 
 great current begins in the Grulf of Mexico, where the 
 water in that land-locked area within the tropics is 
 exceedingly heated ; and flowing out of the gulf it 
 first passes E. and then NE., across the Atlantic and 
 so reaches the European area of the North Sea. So 
 marked is the heat of this immense current, that in 
 crossing from England to America, the temperature of 
 the water suddenly falls some degrees. Several years 
 ago, in crossing the Atlantic, I was in the habit early 
 in the morning of taking the temperature of the water 
 
136 The Gulf Stream. 
 
 with one of the officers of the steam-boat. I then 
 found that at about five o'clock in the morning, for 
 several days, the temperature of the sea was always 
 about 4 degrees above the temperature of the air, but 
 quite suddenly, in passing out of the Gulf stream, at 
 the same hour of the morning the temperature of the 
 water was found to average about 4 degrees below the 
 temperature of the air. Where in the map the arrows 
 point southwards, there are cold streams of water coming 
 from the icy seas of the north. One of these passes 
 along the east coast of America, and coming from the 
 north sea and floating many an iceberg, the western 
 half of the north Atlantic is thus kept cool, and the 
 water is often colder than the air. 
 
 Now the Gulf stream occupies a very great width 
 in the Atlantic, and approaches tolerably near to our 
 own western coast, and the effect of this great body 
 of warm water flowing northward, is to divert the 
 isothermal lines (lines of equal temperature) far to 
 the north, over a large part of the Atlantic area. Thus 
 a certain line runs across North America, about 
 latitude 50, representing an average temperature for 
 the whole year of 32. Aeross that continent it passes 
 tolerably straight, but no sooner does it get well into 
 the Atlantic, than the Gulf stream flowing north- 
 wards, warms the air, and the result is, that the line 
 bends away to the far north above Norway ; thus in 
 
The British Climate. 137 
 
 the west of Europe producing an average warmer 
 climate, of the whole year, than exists in corresponding 
 latitudes in North America, the middle of Europe, and 
 the interior of Asia. Our British climate and all the 
 west of Europe, thus becomes as it were abnormally 
 warm, owing to the influence of the Gulf stream, and 
 you will at once recognise this fact, from the circum- 
 stance that trees of goodly size grow much further 
 north on the west coasts of Europe than on the east 
 coasts of North America. Another effect that the 
 Gulf stream produces, is to cause an unusual amount of 
 moisture in the west of Europe, and if you consult 
 a rain map of the British islands you will see repre- 
 sented by different shades the average amount of rain- 
 fall in different areas the darker the shade the greater 
 the quantity of rain. Now the prevalent winds in the 
 west of Europe are from the SW., and therefore during 
 a great part of the year the south-west wind comes 
 laden with moisture across the land, warm and moist 
 from the sea where the Gulf stream flows. 
 
 In the extreme south-west of England, in Cornwall, 
 about thirty-five inches of rain fall every year; and 
 in the western parts of the north of Scotland, and 
 roughly speaking, over great part of Ireland, the 
 amount of rain-fall is about thirty inches; while for 
 much of the middle and east of England we have a fall 
 of about twenty-five inches. The climate, therefore, of 
 
1 3 8 Climate and Fall of Rain. 
 
 Great Britain is varied in the fall of rain, and the 
 average temperature of the western area is also raised 
 and rendered agreeable by the influence of the Gulf 
 stream. So much is this the case, that certain garden 
 plants grow through the winter in Wales and the West 
 of England, and even in the far north-west of Scot- 
 land, which the winter cold of Middlesex kills. Now 
 this moisture in the air is partly intercepted on its pas- 
 sage eastward by the mountains which rise in the west 
 of the British islands. Every one who has visited 
 Cumberland and Wales knows what rainy regions they 
 are, compared with the centre and east of England, 
 because the moisture that is blown from the Atlantic 
 is precipitated upon the mountains and adjacent lands. 
 The same is the case in Scotland, where the Highland 
 mountains that rise on the west produce the same effect 
 in intercepting the moisture, and thus, partly because 
 it is the first land that the wind laden with moisture 
 reaches, and partly because of the mountains, it happens 
 that a greater amount of rain is precipitated in the 
 western than in the eastern parts of our island. 
 
 Now, if we examine our country with regard to 
 special areas of drainage, we find that they are exceed- 
 ingly numerous. The Spey, which runs into the 
 German ocean, drains an area of very nearly 1,200 
 square miles. The Tay drains an area formed by the 
 Grampian mountains, and part of the Old red sand- 
 
Areas drained by Rivers. 139 
 
 stone of 2,250 square miles. The Forth, includiDg its 
 estuary, drains an area of about 2,000 square miles. 
 The Clyde, not including the greater part of its estuary, 
 drains an area of 1,580 square miles. 
 
 If we take the Trent and the Ouse as draining one 
 area, the immense extent, for such a country as ours, of 
 about 9,550 square miles are drained into the Humber. 
 The Thames drains an area of about 6,000 square 
 miles ; and if we include all the estuary, about 10,000. 
 The Severn drains an area of 8,580 square miles ; and 
 many others of importance might be mentioned, too 
 numerous to name here. 
 
 Now, it is difficult even approximately to settle 
 what -are the geological dates of the valleys through 
 which the rivers run, or, in other words, when they 
 first began to be scooped out, and through what various 
 periods their excavation was intermittently or con- 
 tinuously carried on. No one has yet analysed this 
 subject, and, for my part, I only begin to see my 
 way into it. Nevertheless a little may be done even 
 now, and a great deal will be accomplished when 
 with sufficient data the whole subject may come to 
 be investigated. In Wales, for example, there are vast 
 numbers of rivers and brooks, small and large, and 
 when you examine the relation of these streams to 
 the present surface of the country you often find it very 
 remarkable. Fig. 14 (Map, line 14) is a diagram repre- 
 
140 Dates of River Galleys, &c. 
 
 Fig 14 senting no particular section, but simply 
 
 e the nature of the real sections across the 
 *IQ 
 
 Lower Silurian strata of Cardiganshire, as 
 shown by myself in a paper given to the 
 British Association at Oxford in 1847. The 
 dark-coloured part represents the form of 
 the country, given in the original sections 
 on a true scale of six inches to a mile 
 horizontally and vertically. The strata of 
 this area, and, indeed, of much of South 
 Wales, are exceedingly contorted. The level 
 of the sea is represented by the lower line, 
 and if you take a straight-edge, and place 
 it on the topmost part of the highest hill, 
 and incline it gently seaward, it touches the 
 top of each hill in succession in the man- 
 ner shown by the line 6 b. This line is as 
 near as can be straight, and on the average 
 has an inclination of from one to one-ahd-a- 
 half degrees; and it is a curious circum- 
 stance that in the original lines of section, 
 there were no peaks rising above that line, 
 they barely touched it as in the diagram, 
 and no more. It occurred to me, when I 
 first observed this circumstance, that, at a 
 period of geol ogical history of unknown date 
 perhaps older than the beginning of the 
 
Valleys in South Wales. 141 
 
 New red sandstone, this inclined line that touches 
 the hill-tops must have represented a great plain of 
 marine denudation. 
 
 The sea waves on the cliffs by the shore are the only 
 power I know that can denude a country, so as to 
 shave it across and make a plain either horizontally 
 or slightly inclined. If a country be sinking very 
 gradually, and the rate of waste by the waves on the 
 shore be proportionate to the rate of sinking, a little 
 reflection will show you that the result would be a 
 great inclined plane like that of the straight line b b in 
 the diagram. Let South Wales be such a country : 
 then when that country was again raised out of the 
 water, the streams made by its drainage immediately 
 began to scoop out valleys ; and though some of the 
 valleys may have been begun by marine denudation 
 during the process of emergence, yet in the main 
 I believe that the inequalities below the line b b have 
 been taade by the influence of running water. Hence 
 the number of deep valleys, many of them steep-sided, 
 that diversify Wales, all the way from the Towey in 
 Caermarthenshire to the southern flanks of Cader Idris 
 and the Arans. On ascending to the upper heights, in- 
 deed, anywhere between the Vale of Towey and Cardigan 
 Bay, it is impossible not to be struck with the average 
 uniformity of elevation of the flat-topped hills that form 
 a principal feature of the country. Between the rivers 
 
142 River Valleys and 'Table- Lands. 
 
 Towey and Teifi, and in other areas, these hills in fact 
 form the relics of a great plain or table-land in which 
 the valleys have been scooped out ; and in the case of 
 the country represented in fig. 14, ' the higher land, as 
 it now. exists, is only the relics of an average general 
 gentle slope represented by the straight line (6 6) drawn 
 from the inland heights towards the sea.' * My col- 
 league, Mr. Jukes, has lately applied and extended 
 the scope of the same kind of reasoning to the south 
 of Ireland, with great success. In various parts of 
 Europe, notably in those regions that have been longest 
 above the water on the banks of the Moselle and of 
 the Ehine you find innumerable valleys, intersecting 
 table-lands of a form that leads you to believe that they 
 have been made by the long-continued action of run- 
 ning waters, and I believe that the South Wales valleys 
 have been formed in a great measure in the same way. 
 But when we come to the region of the larger rivers, 
 there is a great deal that is difficult to account for. 
 One thing is certain, that before the glacial epoch, which 
 I described with so much detail in the last lecture, the 
 greater contours of the country were much the same as 
 they are now. The mountains of Scotland, Wales, and 
 of Cumberland, and the great Pennine chain, existed 
 then as now ; the central plains of England were plains 
 then, and the escarpments of the Chalk and Oolites 
 * Keports, British Association, p. 66, 1847. 
 
The Severn. 143 
 
 existed before the glacial period. All that the ice did 
 was to modify the surface by degradation, to smooth its 
 asperities by rounding and polishing them, to deepen 
 valleys where glaciers flowed, and to scatter quantities 
 of detritus in the shape of boulder-clay and sands and 
 gravels, over the plains that form the east of England, 
 and the Lias and New red sandstone in the middle. 
 If we examine the valley of the Severn from Bristol 
 northwards through Coalbrook Dale, we find that for 
 a large part of its course the river runs down a great 
 valley between the old palaeozoic hills and the escarp- 
 ments formed by the table-land of the Cotswold range, 
 that rises so high in the neighbourhood of Cheltenham. 
 That valley certainly existed before the glacial epoch, 
 because we find boulders and boulder drift far down 
 towards Tewkesbury, and therefore I believe, that 
 before the glacial epoch this part of the Severn ran 
 very much in the same course that it does at present. 
 Then the country sank beneath the sea, and Plinlimmon 
 itself, where the river rises, was buried in part, or 
 possibly altogether, beneath the waters. When the 
 country again emerged, the old system of river-drainage 
 in that area was resumed, and the Severn following in 
 the main its old course, cut a channel for itself through 
 the boulder-clay that partially blocked up the original 
 valley in which it ran. But when that original valley 
 was formed through which the older Severn ran, no 
 
144 'fhe Forth and Clyde. 
 
 man can yet say, although England having probably 
 been above the sea during great part, or perhaps the 
 whole of the undoubted Miocene epoch, it is likely 
 that some of our greater contours were then first begun, 
 or if not begun, carried on, and very seriously modified. 
 Again if we take the rivers Forth and Clyde ; as I 
 explained to you in a previous lecture, the areas occu- 
 pied by these rivers and by the rocks through which 
 they run, is an exceedingly ancient area of depression. 
 That country is also covered more or less with boulder 
 clay, and with later stratified detritus of sand and 
 gravel which were formed in part by the remodelling of 
 the glacial drifts. The great rivers I believe ran in 
 that area before the commencement of these deposits, 
 and for aught I know to the contrary for very long 
 before that period. But we have no perfectly distinct 
 traces of these earlier epochs in that part of Scotland, 
 and all we know is that rivers ran in these valleys 
 before the deposition of the boulder clay, and resumed 
 to some extent their old courses after the emergence 
 of the country. Again, if we examine the channels of 
 other rivers in the east of England, as for instance the 
 Ouse in Bedfordshire we find that some of them flow 
 through areas covered with this clay, and have cut 
 themselves channels through it in such a way as to 
 lead to the inference that the valleys in which they run 
 did not exist before the boulder-bed period, but that 
 
The Ouse and Thames. 145 
 
 they have cut their courses through it and the under- 
 lying Oolitic strata, and formed anew system of valleys. 
 These, however, are exceptional, and often only apply 
 to parts of their channels. 
 
 Again, with regard to the Thames, it is remarkable 
 that it rises in the Seven Springs not far from the edge 
 of the Oolitic escarpment of the Cotswold hills that 
 overlook the Severn, which runs in the valley about 
 1,000 feet below. The infant Thames thus flows at 
 first across a broad table-land of Oolite, and by and 
 by comes to a second table-land, formed of the Chalk, 
 and the wonder is, that there its course was not turned 
 aside by that high escarpment. Instead of that being 
 the case, a valley cuts right across the escarpment of 
 chalk, through which the river flows. This escarp- 
 ment is exceedingly old dating from long before the 
 boulder-beds, but how long no one knows, for we find 
 far-transported boulders in places at its base, while in 
 the same neighbourhood the drift has not been depo- 
 sited on its slopes nor yet does it lie on the top. How 
 did the Thames find its way through what was once 
 that great unbroken scarped barrier of chalk now called 
 the Chiltern Hills ? Not that such phenomena are con- 
 fined to this river alone it is a trick that rivers have ; 
 they will cut through escarpments in what seems an 
 unnatural fashion. Mr. Jukes, in a paper read before 
 the Geological Society in June 1862, on the Kiver- 
 
 L 
 
146 Influence of 'Time and Rivers. 
 
 valleys of the South of Ireland, has attempted an ex- 
 planation of this, with regard to those rivers, and I 
 firmly believe that his solution holds good in many 
 cases in England, as for instance in those that cut 
 across the escarpments of the Weald mentioned at 
 page 82. In the south of Ireland, Mr. Jukes finds that 
 some rivers break suddenly right across chains of hills, 
 and his explanation of the circumstance is that when a 
 certain river began to flow, the surface of the country 
 formed a kind of inclined plain, in the manner shown 
 at p. 140, part of that old surface being then the top 
 of the range of hills across which the river now flows ; 
 and just in proportion as it cut a channel downwards 
 so as to form the present valley at the foot of, and 
 along the strike of the hills, so without needful frac- 
 ture it also deepened by degrees its channel across the 
 range. It is astounding when first thought about, 
 because the time required to perform such an operation 
 is so stupendous that the mind almost refuses to grapple 
 with it. But the more we ponder on geological time, 
 the more is required for every individual subject; and 
 I for one easily grant it for the channel-cutting power 
 of rivers. 
 
 I will show you, however, that this process may 
 not necessarily always be required to cut a passage 
 through a range such as the Chalk escarpment. If you 
 follow the Oolitic strata northwards, you will see that 
 
Breaching of Escarpments. 147 
 
 they pass into the channel of the Humber, and reap- 
 pearing on the opposite side, pass north into Yorkshire. 
 The Chalk escarpment does the same, and both lie 
 low. Now by the side of the Humber, both Chalk and 
 Oolites are at the level of the sea, and it is possible 
 that the sea beating upon the rocks, during various old 
 oscillations of level, before the drift period, may in the 
 course of time have cut a channel for itself across the 
 ranges of low Chalk and Oolitic hills in that area now 
 partly occupied by the estuary of the Humber. If 
 this be true, the sea effected a breach in the rocks. 
 Then suppose these lands to have been heaved up, so 
 that the present salt-water estuary became high and 
 dry; the river then ran through it, and we have 
 a river-valley cutting right across the escarpment. 
 It seems not impossible, that at an old period of the 
 history of the estuary of the Thames, the escarpment 
 of the Chalk through which the river now flows may 
 at a lower, level have been breached by the sea in the 
 way I have supposed with the estuary of the Humber. 
 Then, the whole being heaved up, the Thames flowed 
 through the gap in the Chiltern hills, and across the 
 London clay down to the present sea. Though worth 
 consideration, I do not however depend on this hypo- 
 thesis, for as I have no doubt that the gaps both of the 
 Humber and the Thames are of far older date than the 
 glacial period, their precise origin is in the present 
 
 L 2 
 
148 River Terraces. 
 
 state of the subject lost in the mists of geological 
 antiquity. It may be that Mr. Jukes' hypothesis may 
 apply even to the Thames, the Ouse, and the Humber, 
 the origin of their scarp-cutting valleys dating from a 
 time inconceivably remote in years, when both Cretaceous 
 and Oolitic rocks spread much further west than they 
 do now, having with a low eastern dip in some old 
 period been simply cut by denudations into an in- 
 clined plane sloping east, in a manner analogous to 
 that of the Weald already described. 
 
 On the banks of the Thames and many other rivers 
 there are frequent terraces. It is one of the effects 
 produced by the action of rivers to form terraces upon 
 their banks ; close to or at a distance from the river as it 
 now is, according to its size and other circumstances. 
 The hills on either side are, perhaps, made of solid rock, 
 or of softer strata, as the case may be, and the terraces 
 lying between the higher slopes and the rivers consist 
 of gravel, sometimes of old date, remodelled by these 
 rivers as they cut their way from side to side, thus by 
 degrees deepening their valleys. A river for instance 
 at one time flowed over the top of the highest gravel 
 terrace, and winding about from side to side of the 
 valley and cutting away detritus in its course, it formed 
 various terraces one after another, the terrace on the 
 highest level being of oldest date, and that on the 
 lowest level that bounds the modern alluvium the 
 
River 'Terraces. 
 
 latest. Thus in the following figure, Nos. 1 and 2 
 represent the solid rocks of a country bounding a 
 wide valley partly filled with ancient gravel, No. 3, 
 which originally filled the valley from side to side as 
 
 Fig. 15. 
 
 high as the uppermost dotted line 4, but a river flow- 
 ing through by degrees bore part of the loose detritus 
 to a lower level, thus cutting out the terraces in suc- 
 cession marked No. 5, 6, and 7. Or again, in other 
 cases (as in the Moselle for example), where no special 
 valley of the present shape existed before the drainage 
 took the general direction of its present flow, the river 
 has actually excavated its own valley by the destruction 
 of the solid rocks through which it flows. In the occa- 
 sional terraces which accompany processes such as this, 
 it often happens that alluvial and gravelly deposits are 
 left marking ancient levels of the rivers. Or it some- 
 times happens that when the physical geography of the 
 country was a little different from what it is now, such 
 an ancient valley was in places partly filled by irregular 
 strata deposited by the river itself (as in the Ouse 
 near Bedford), through which in time, as circumstances 
 changed, the river cut its way, and formed terraces as 
 
150 River Gravels. 
 
 in fig. 15. It is in the gravel, sand, and loam of such 
 terraces that the works of old races of men have often 
 been found along with the bones of extinct animals. 
 
 In the year 1847, a French savant, Mons. Boucher 
 de Perthes, of Abbeville, published an account of these 
 remains in the first volume of his ( Antiquites Celtiques.' 
 In examining the old gravels of the river Somme, he 
 discovered the remains of terrestrial animals, some of 
 them of extinct species. The strata consisted of surface 
 soil, below which was nearly five feet of brown clay, then 
 loam, then a little gravel containing land shells, and 
 along with these shells the teeth of the Mammoth. 
 Below that, there occurred white sand and fresh-water 
 shells, and again the bones and teeth of the Mammoth 
 and other extinct species ; and along with these bones 
 and teeth, a number of well-formed flint hatchets. 
 Geologists were for long asleep on this subject. Mons. 
 de Perthes had printed it many years, but none of 
 them paid much attention to him. At length, Mr. 
 Prestwich having his attention drawn to the subject, 
 began to examine the question. He visited Mons. de 
 Perthes, who distinctly proved to him and afterwards 
 to other English geologists that what he had stated 
 was incontestably the fact. These hatchets are some- 
 what rude in form, but when I say 'rude,' I do 
 not mean that there is any doubt of their having been 
 formed artificially. They are not polished and finished, 
 
Flint Implements. 151 
 
 like those brought from the South Sea Islands ; but 
 there can be no doubt whatever that they have been 
 formed by the hand of man ; and I say this with 
 authority, since, for more than twenty-five years, I 
 have been daily in the habit of handling stones, and no 
 man who knows how chalk flints are fractured by nature, 
 would doubt the artificial character of these ancient tools 
 or weapons. 
 
 Of late the same kind of observations have been 
 made in our own country. In the neighbourhood of 
 Bedford on the Ouse, there are beds of river gravel of 
 this land which rise about 25 feet above the level of 
 the river lying in broad terraces ; and in one of these, 
 far above the level of the river, there have been found 
 associated with river shells, the bones of the Mammoth, 
 old varieties of oxen, and various other mammalia, and 
 along with these a considerable number of flint hatchets. 
 By the river Waveney also, on the borders of Norfolk 
 and Suffolk, near Diss, the same phenomena have been 
 observed in old gravel pits, made for the extraction of 
 road materials ; and it has been proved that near 'the 
 mouth of the estuary of the Thames between the Ke- 
 culvers and Herne Bay, flint hatchets have fallen 
 from the top of a cliff of Eocene sand capped with 
 recent gravel. These were first noticed by Mr. T. 
 Leech, and I have myself found one of them partly 
 water-worn by the waves. No bones have as yet 
 
152 Man and the Mammoth. 
 
 been observed in that district along with the imple- 
 ments. But it is very clear that the bones of Elephas 
 primigenius and of other extinct mammalia occur 
 in many places associated with the works of pre- 
 historic men. As yet, however, the bones of men 
 have never in our country been discovered along with 
 them in the gravels. In certain British caves in 
 limestone rocks such as Kent's hole near Torquay, 
 Brixham cave in the same county, those in Gower, 
 Glamorganshire, and in several others, remains of the 
 Mammoth, two species of Ehinoceros, together with the 
 Cave bear, Hyaena, and many other animals of species 
 both extinct and still living have been found, and with 
 these not only flint knives, flakes, and hatchets were 
 discovered, but implements made of bone, such as 
 needles or hair pins, and various other articles. On 
 the continent of Europe, also, in caverns in the lime- 
 stone on the river Meuse in Belgium, Dr. Schmerling 
 found bones of men and other living species mingled 
 with those of extinct mammals, such as the Cave bear, 
 Hyaena, Elephant, and Ehinoceros. His account, long 
 slighted, though full of errors of detail, has at length 
 obtained the attention it deserved. Further, within the 
 last few years, in the surface strata called the Loess of 
 the same river near Maestricht, human skeletons are said 
 to have been actually found. I have seen these remains, 
 which certainly have an antique look, but some doubt 
 
Raised Beaches and terraces. 1 53 
 
 exists as to their authenticity. In the same neigh- 
 bourhood, however, it is certain that a human jaw was 
 found in strata containing the remains of Mammoths, 
 &c. Many other examples might be given of the re- 
 mains of old races of men in such like caverns or in 
 river deposits, but enough has been said to show that 
 there can be no doubt that man was contemporary in 
 our island and elsewhere with extinct mammalia, and 
 it is possible that his origin in our island dates as far 
 back as the time when the country was united to the 
 mainland, and that along with the great hairy Mammoth, 
 the Hippopotamus, the Irish Elk, and the Khinoceros he 
 travelled across, at a time when the arts were so rude 
 that he had no other means of coming except upon his 
 feet. 
 
 One word more on a kindred subject, and then I 
 shall close this lecture. Eound great part of our coast 
 we find terraces, from twenty to fifty feet above the 
 level of the sea, and in some places the terrace runs 
 with great persistence for a number of miles. Kound 
 the Firth of Forth, for example, on both shores, there 
 is an old sea-cliff of solid rock, overlooking a raised 
 beach or terrace, now often cultivated in cornfields and 
 meadows, and then you come to the present sea beach. 
 This terrace usually consists of gravel and sea-shells in 
 great quantities, of the same species with those that lie 
 upon the present beach, where the tide rises and falls 
 
154 Ancient Canoes. 
 
 every day. The same kind of terrace is found on the 
 shores of the Firth of Clyde, and in almost all the 
 other estuaries of Scotland, and in places round the 
 west highlands on the coast of Scotland. Similar or 
 analogous raised beaches occur on the borders of Wales, 
 and in the south of England. In Devon and Cornwall, 
 there are the remains of old consolidated beaches clinging 
 to the cliffs from twenty to thirty feet above the level 
 of the sea. It is clear, therefore, that an elevation of 
 the land has occurred in places to the extent of about 
 forty feet, at a very recent period, long after all the 
 living species of shell-fish inhabited our shores. Fur- 
 ther, in the alluvial plains that border the Forth, and 
 on the Clyde in the neighbourhood of Glasgow, at 
 various times, in cutting trenches, canals, and other 
 works, the bones of whales, seals, and porpoises have 
 been found at a height of from twenty to thirty feet 
 above the level of high water-mark. Now it is evident 
 that whales did not crawl twenty or thirty feet above 
 high water-mark to die, and therefore they must either 
 have died upon the spot where their skeletons were 
 found or been floated there after death. That part of 
 the country therefore must have been covered with 
 salt water, which is now occupied simply by common 
 alluvial detritus. But the story does not stop there, 
 for in the very same beds in which the remains of these 
 marine mammalia have been discovered on the Clyde, 
 
Roman Remains. 155 
 
 canoes have been found in a state of preservation so 
 perfect, that all their form and structure could be 
 well made out. Some of them were simply scooped in 
 the trunks of large trees, but others were built of 
 planks nailed together, square-sterned boats indeed, 
 built of well dressed planks, and the inference has 
 been drawn by my colleague, Mr. Geikie, who has de- 
 scribed them, that this last elevation took place at a 
 time that is historical, and even since the Koman occu- 
 pation of our island. 
 
 There is one piece of evidence with respect to the 
 very recent elevation of these terraces which I think is 
 deserving of great attention, and it is this: In the 
 neighbourhood of Falkirk, on the south shore of the 
 Firth of Forth, there is a small stream, and several 
 miles up that stream, beyond the influence of the tide 
 of the present day, there were at the end of last 
 century remains of old Eoman docks, near the end of 
 the Eoman wall usually called the wall of Antoninus 
 that stretched across Scotland from the Firth of Clyde 
 to the Firth of Forth. Those docks are now no longer 
 to be seen : but so perfect were they, that General Eoy 
 was able to describe them in detail, and actually to 
 draw plans of them. When they were first built they 
 were of course close to the tide, and stood on the 
 banks of a stream called the Carron, believed by 
 Mr. Greikie to have been tidal ; but the sea does not 
 
156 The Wall of Antonine. 
 
 come near to them now ; and therefore he naturally 
 inferred, that when they were constructed the relative 
 height of the land to the sea must have been less than 
 at present. Again, the great wall of Antoninus, erected 
 to keep out the northern barbarians from the territory 
 conquered by the Roman legions, must have been 
 brought down close to the sea level at both ends. Its 
 eastern termination is recognised by most antiquarians 
 as having been placed at Carriden, on the top of a 
 considerable cliff, where the great Falkirk flats disap- 
 pear along the shore. Its western extremity, not having 
 the favourable foundation of a steep rising ground, now 
 stands a little way back from the sea-margin of the 
 Clyde. When it was built it was probably carried to 
 the point where the chain of the Kilpatrick Hills, 
 descending abruptly into the water, saved any further 
 need for fortification. But owing to a probable rise of 
 the land, a level space of ground twenty or twenty-five 
 feet above the sea now intervenes between high water- 
 mark and the base of the hills and runs westward 
 from the termination of the wall for several miles as 
 far as Dumbarton. Had this belt of land existed then, 
 there appears little reason to doubt that the Romans 
 would not have been slow to take advantage of it, so 
 as completely to prevent the Caledonians from crossing 
 the narrow parts of the river, and drive them into the 
 opener reaches of the estuary below Dumbarton. 
 
LECTURE VI. 
 
 QUALITIES OF WATERS. CONNECTION OF THE PHYSICAL 
 GEOLOGY OF THE COUNTRY WITH THE POPULATION. 
 
 IN last lecture I gave a sketch of the chief river 
 areas of Great Britain, but I did not enter upon 
 one important point connected with them, namely, the 
 qualities of their waters. If we examine the geological 
 structure of our island, with regard to its water-sheds 
 and river courses, we find that the larger streams, with 
 one or two exceptions, run into the German Ocean, the 
 chief exception being the Severn and its tributaries, 
 which drain a large proportion of Wales, and a con- 
 siderable part of the interior of England. The reason 
 why the larger rivers run chiefly to the east is, that in 
 consequence of the nature of old disturbances and 
 denudations of the rocks, the main water-shed of the 
 country from the north of Scotland far into England 
 is nearer to the western coast than to the eastern, 
 and thus it is that a much larger area of country is 
 
158 Waters of the Highlands. 
 
 drained towards the east than to the west. On the 
 west side of England we have more than one tract 
 of high ground, and in the middle and east, plains and 
 table-lands of which I had occasion to speak in a 
 former lecture, and the area occupied by these flats 
 being much larger than the western hilly districts, the 
 rivers there are larger, with, as I have already said, 
 the exception of the Severn. 
 
 Now, when we look at the qualities of the waters of 
 rivers, we find that this depends on the nature of the 
 rocks and soils over which they flow. Thus the waters 
 of the rivers of Scotland are, for the most part, soft. 
 All the Highland waters, as a rule, are soft ; the moun- 
 tains being composed of granitic rocks, gneiss, mica- 
 schist and the like, a very small proportion of limestone 
 being intermingled therewith, and the other rocks 
 being comparatively free from lime. Only a com- 
 paratively small proportion of lime, soda, or potash, is 
 taken up by the water that falls upon, flows over, or 
 drains through these rocks, the soda or potash being 
 chiefly derived from the feldspathic ingredients of the 
 various formations, and therefore the waters are soft. 
 For this reason, a few years ago, at a vast expense, 
 Glasgow was supplied with water derived from Loch 
 Katrine, which, lying amid the gneissic rocks, is like 
 almost all other waters from our oldest formations, 
 peculiarly soft, pure and delightful. The same is the 
 
Waters of Wales, &c. 159 
 
 case with the waters that run from the Silurian rocks 
 of the Lammermuir hills, except where these are covered 
 by a drift of foreign materials. 
 
 The water from the Welsh mountains is also in 
 great part soft, the country being composed of Silurian 
 rocks, here and there slightly calcareous from the pre- 
 sence of fossils mixed with the hardened sandy or slaty 
 sediment, that forms the larger part of that country. 
 From this cause so sweet and pleasant are the waters 
 of Bala lake, compared with the impure mixtures we 
 drink in London, that it has been more than once pro- 
 posed to lead it all the way for the supply of water for 
 the capital. But when in Wales and on its borders we 
 come to the Old red sandstone district, the marls are 
 somewhat calcareous, and interstratified with impure 
 concretionary limestones, called cornstones, and the 
 waters are hard. The waters are apt to be still harder 
 in the Carboniferous limestone tracts that sometimes 
 rise into high and almost mountainous ridges round the 
 borders of the great South Wales coal-field, and in 
 Flintshire and Denbighshire. Again, the waters which 
 flow from the Pennine chain, that extends from the 
 southern borders of Scotland into Derbyshire, are all 
 hard, because they drain areas composed chiefly of 
 Carboniferous limestone ; and all the rivers that run east 
 from this range, and all those that flow in areas as- far 
 south as the British Channel, over the New red sand- 
 
160 Salts in Solution Bath Wells. 
 
 stone and Lias, and the Oolitic and the Cretaceous 
 rocks, are of necessity charged with those substances in 
 solution that make water hard. 
 
 Before proceeding to other subjects I should like to 
 give you some idea of the quantity of certain salts 
 which are carried in solution into the sea by the agency 
 of running water. 
 
 The first case I shall take is at Bath, where there is 
 a striking example of what a mere spring can do. The 
 Bath Old well yields 126 gallons of water per minute, 
 which is equal to 181,440 gallons per day. There are 
 a number of constituents in this water, such as car- 
 bonate of lime, nearly nine grains to the gallon; 
 sulphate of lime, more than eighty grains to the gallon ; 
 sulphate of soda, more than seventeen grains to the 
 gallon ; common salt, rather more than twelve and 
 a half grains to the gallon ; chloride of magnesium, 
 fourteen and a half grains to the gallon ; etc. etc. 
 altogether, with other minor constituents, there are 
 144 grains of salts in solution in every gallon of this 
 water, which is equal to 3,402 Ibs. per day, or 420 tons 
 a year. Now a cubic yard of limestone may be roughly 
 estimated to weigh one ton. If, therefore, these salts 
 were precipitated, compressed, and solidified into the 
 same bulk as limestone, we should find the annual dis- 
 charge of the Bath wells to form a square column 9 feet 
 in diameter and about 140 feet high. Yet this large 
 
'Thames Water. 161 
 
 amount of solid mineral matter is carried away every 
 year in invisible solution in water which, to the eye, 
 appears perfectly limpid and pure. 
 
 Again, the Thames is a good type of what maybe 
 done in this way by a moderate-sized river, draining 
 a country which to a great extent is composed of calca- 
 reous rocks. It rises in the middle of England at the 
 Seven Springs, near the western edge, and therefore 
 not far from the top of the great Oolitic table-land, 
 of the Cotswold hills, and flows eastward through all 
 the Oolitic strata, which are composed mostly of thick 
 formations of limestone, calcareous sand, and masses 
 of clay, which often contain shelly bands and scattered 
 fossil shells. Then, bending to the south-east, below 
 Oxford, it crosses the Lower greensand, the Grault, the 
 Upper greensand, and the Chalk, the last of which 
 may be roughly stated as consisting of nearly pure 
 limestone ; then through the London clay, and other 
 strata belonging to the great Eocene formation of the 
 London basin, which are nearly all more or less cal- 
 careous. The Thames may therefore be expected to 
 contain numerous substances of various kinds in solu- 
 tion in large quantities; and to those derived from the 
 rocks must be added all the impurities from the drainage 
 of the villages and towns that line its banks between 
 the Seven Springs and London. 
 
 At Teddington, on a rough average, 1,337 cubic feet 
 M 
 
1 62 Chemical Solutions in Water. 
 
 of water (equal to 8,329 gallons) pass seaward per 
 second ; and upon analysis it was found that twenty-two 
 and a half grains of various matters, chiefly bicarbonate 
 of lime, occur in solution in each gallon, thus giving 
 187,402 grains per second passing seaward. This is 
 equal to 87,844 Ibs. per hour, or 33,497 tons per annum, 
 and this amount is almost entirely dissolved out of the 
 bulk of the solid rocks and surface soils of the country, 
 and is passing out to sea in an invisible form, and only 
 known to the analytical chemist. If you consider that 
 this is only one of many rivers that flow over rocks 
 which contain lime and other substances easily soluble, 
 you will then see what an enormous quantity of matter 
 by this to the eye perfectly imperceptible process is 
 being gradually carried into the sea. And it is a neces- 
 sary part of the economy of nature that it should be so, 
 for it is from salts thus obtained by the sea that plants 
 and shell-fish derive, to some extent, their nourish- 
 ment. 
 
 This waste of material by the dissolving of rocks is 
 indeed evident to the practised eye over most of the 
 solid limestone districts of England, and I shall there- 
 fore say a little more on the subject. On the flat tops 
 of the Chalk Downs, for example, over large areas in 
 Dorsetshire, Hampshire, and Wiltshire, quantities of 
 angular unworn flints, many feet in thickness, com- 
 pletely cover the surface of the land, revealing to the 
 
Dissolving of Chalk. 163 
 
 thoughtful mind the fact that all these thick accumula- 
 tions of barren stones have not been transported from 
 a distance, but rather represent the gradual destruction 
 by rain and carbonic acid of a vast thickness of chalk 
 with layers of flint that once existed above the present 
 surface. The following diagram will explain this. 
 
 Fig. 16. 
 
 1, Chalk without flints. 2, Chalk with flints, a a, the present surface 
 of the ground marked by a dark line, b b, an old surface of ground, 
 marked by a light line. Between a a the surface is covered by accu- 
 mulated flints, the thickness of which is greatest where the line is 
 thickest between a' and x , above which surface a greater proportion of 
 chalk has been dissolved and disappeared^ 
 
 There can be little doubt but that the great plateaus 
 of Carboniferous limestone and Oolite have suffered 
 waste by solution, equal to that of the Chalk, only from 
 the absence in them of flints-'we have no insoluble 
 residue by which to estimate its amount. 
 
 The soils of a country necessarily vary to a great 
 extent, though not entirely, with the nature of the un- 
 derlying geological formations. Thus, in the Highlands 
 of Scotland the gneissic and granitic mountains are 
 generally heathy and barren, because their hard rocky 
 materials frequently corne bare to the surface over great 
 areas. Strips of more fertile meadow land lie chiefly 
 
 in 2 
 
164 Mountain Soils. 
 
 on narrow alluvial plains, which here and there border 
 the rivers. Hence the Highlands mainly form a wild 
 and pastoral country, sacred to grouse, black cattle, sheep 
 and red deer. Further south similar rocks, though the 
 scenery is different, yet produce more or less the same 
 kind of soil, in the broad range of hills that lies 
 between the great valleys of the Clyde and Forth, 
 and the borders of England, including the Moorfoot 
 and the Lammermuir hills, and the high grounds that 
 stretch southwards into Carrick and Galloway. The 
 rocks there, being composed of hard untractable gritty 
 and slaty material, form but little soil, because they 
 are difficult to decompose. Hence the ground being 
 mostly high, is to a great extent untilled, though ex- 
 cellently adapted for pastoral purposes. Where, how- 
 ever, the slopes descend, and are covered more or less 
 with old ice drifts and moraine matter, the soil is 
 deeper and the ground is more fertile. 
 
 The great central valley of Scotland, between the 
 metamorphic rocks of the Highland mountains and the 
 less altered Silurian strata of the high-lying southern 
 counties, is occupied by rocks of a more mixed charac- 
 ter, consisting of Old red sandstone and marl, and of 
 the shales, sandstones and limestones of the Coal-mea- 
 Bures intermixed with considerable masses of igneous 
 rocks. The effect of denudation upon these various 
 rocks in old times, particularly of the denudation which 
 
Mountain Soils. 165 
 
 took place during the glacial period, and also and more 
 especially of the rearrangement of the ice-borne debris 
 by subsequent marine action, as the country sunk 
 beneath the sea and rose again, has been to cover large 
 tracts of country with a happy mixture of materials 
 such as clay, mixed with pebbles, sand and lime. In 
 this way one of the most fertile tracts anywhere to be 
 found in our island has been formed, and its cultiva- 
 tion for nearly a century has been taken in hand by 
 skilful farmers who have brought agriculture over great 
 part of that district up to the very highest pitch which 
 it has ever attained in any part of Great Britain. 
 
 Through the inland parts of England from Northum- 
 berland to Derbyshire, we have another long tract of 
 hilly country, composed of paleozoic rocks, forming 
 in part such high regions that much of it is unfitted 
 for ordinary agricultural operations. A considerable 
 part of it is therefore devoted to pasture land, as is 
 also the case with large portions of Cumberland and 
 the other north-western counties of England. The same 
 features are observable in Wales, where disturbance of 
 the palasozoic rocks has resulted in the elevation of a 
 great range, or rather of a cluster of mountains the 
 highest south of the Tweed. In that old Principality 
 and in the Longmynd of Shropshire there are great 
 tracts of land, amounting to thousands upon thousands 
 of acres, where the country rises to a height of from 
 
1 66 Mountain Soils. 
 
 1,000 to 3,500 feet above the level of the sea. Much 
 of it is covered with heath and is therefore fit for 
 nothing but pasture land ; but on the low grounds 
 and on the alluvium of the rivers, there is often excel- 
 lent soil. When we come to the eastern part of this 
 hill-country in Monmouthshire, Brecknockshire, Here- 
 fordshire, and parts of Worcestershire, occupied by the 
 Old red sandstone, the larger proportion of the country 
 though hilly, and in South Wales occasionally even 
 mountainous is naturally of a more fertile kind, from 
 the circumstance that the rocks are much softer and 
 therefore more easily decomposed ; and where the 
 surface is covered with drift, the loose material is 
 chiefly formed of the waste of the strata on which it 
 rests, and this adds to its fertility. The soil is thus 
 deepened and more easily fitted for purposes of tillage. 
 In the centre of England, in the Lickey hills, near 
 Birmingham, and in the wider boss of Charnwood 
 Forest, where the old palaeozoic rocks crop out like 
 islands amid the Secondary strata, it is curious to 
 observe that a wild character suddenly prevails in the 
 scenery, for the rocks are rough and untractable, and 
 stand out in miniature mountains. Much of Charn- 
 wood Forest is, however, covered by drift, and is now 
 being so rapidly enclosed, that, were it not for the 
 modern monastery and the cowled monks who till 
 the eoil, it has almost ceased to be suggestive of the 
 
Soils of the New Red Sandstone. 167 
 
 England of mediaeval times, when wastes and forests 
 covered half the land. 
 
 If now we pass to the Secondary rocks that lie in the 
 plains, we find a very different state of things. In the 
 centre of England formed of New red sandstone and 
 marl, the soils are for the most part more fertile than 
 in the mountain regions of Cumberland and Wales, or 
 in some of the Palaeozoic areas in the extreme south- 
 west of England. When the soft red sandstone and 
 marl are bare of drift, and form the actual surface, 
 they often decompose easily, and form deep loams, save 
 where the conglomerate beds, lying in the middle of 
 the New red sandstone, come to the surface. These 
 conglomerates consist to a great extent of gravels barely 
 consolidated, formed of well waterworn rounded pebbles, 
 of various kinds, but chiefly of liver-coloured quartz- 
 rock derived from some unknown region, and of sili- 
 ceous sand, sometimes ferruginous. This mixture forms 
 therefore, to a great extent, an exceedingly barren soil. 
 Some of the old waste and forest lands of England, 
 such as Sherwood Forest and Trentham Park, lie 
 almost entirely upon these intractable gravels, or on 
 other barren sands of the New red sandstone, and have 
 partly remained uncultivated to this day. As land 
 however becomes in itself more valuable, the ancient 
 forests are being cut down and the ground enclosed. 
 But a good observer will infer from the straightness and 
 
1 68 Red Marly Soils. 
 
 smallness of the hedges, that such ground has only been 
 lately taken into cultivation, and at a time since it has 
 become profitable to reclaim that which at no distant 
 date was devoted to forest ground and to wild animals. 
 In the centre of England there are broad tracts of 
 heavy land composed chiefly of New red marl and Lias 
 clay. When you stand, as I stated in a previous lec- 
 ture, on the summit of the great escarpment, formed by 
 the Oolitic table-land, you look over the wide flats and 
 undulations formed of this New red marl and Lias 
 clay. The marl consists of what was once a light kind 
 of clay, mingled with a small per-centage of lime, 
 and when on the surface it again moulders down, it 
 naturally forms a fertile soil. A great extent of the 
 arable land in the centre and west of England is 
 formed of these red strata ; and it is worthy of notice 
 that the fruit-tree districts of Great Britain lie chiefly 
 upon red rocks, sometimes of the Old and sometimes 
 of the New red series. The counties of Devonshire, 
 Herefordshire, and Gloucestershire, with their numerous 
 orchards, celebrated for cider and perry, lie in great 
 part on these formations, where all the fields and 
 hedgerows are in spring white with the blossoms of 
 innumerable fruit trees. Again, in Scotland the plain, 
 called the Carse of Gowrie, lying between the Sidlaw 
 Hills and the Firth of Tay, stretches over a tract 
 of Old red sandstone, and is famous for its apples. 
 
Lias Soils. 169 
 
 What may be the reason of this relation I do not know ; 
 but such is the fact, that soils composed of the New 
 and Old red marl and sandstone are better adapted for 
 fruit trees than any other in Britain. 
 
 The Lias clay in the centre of England forms a con- 
 siderable proportion of our meadow land. It is blue 
 when unweathered, and includes many beds of lime- 
 stone, and bands of fossil shells scattered throughout the 
 clay itself. From its exceeding stiffness and persistent 
 retention of moisture, it is especially adapted for grass 
 land, for it is not easy to plough, and thus a large 
 proportion of it in the centre of England is devoted to 
 pastures intersected by innumerable foot-paths of ancient- 
 date, that lead by the pleasant hedge-rows to wooded 
 villages and old timbered farms. When we pass into 
 the Middle Lias, which forms an escarpment over- 
 looking the Lower Lias clay, we find a very fertile soil ; 
 for the Marl stone, as it is called, is much lighter in 
 character than the more claye} 7 Lower Lias, being 
 formed of a mixture of clay and sand with a con- 
 siderable proportion of lime, derived from its numerous 
 fossils. The course of the low flat-topped Marlstone 
 hills striking along the country and overlooking the 
 Lower Lias clay, is thus usually marked by a strip of 
 peculiarly fertile soil, often dotted with villages and 
 towns with antique churches and towers built of the 
 brown limestone of the formation. 
 
170 Soils of the Oolitic Rocks. 
 
 When we ascend into the next geological group, we 
 find the Oolitic Downs, formed, for the most part, of 
 beds of limestone, with here and there interstratified 
 clays, some of which, like the Oxford and Kimeridge 
 clays, are of great thickness, and spread over con- 
 siderable tracts of country. The flat tops of these 
 limestone Downs, when they rise to a considerable 
 height, as they do on the Cotswold hills, were until a 
 very recent date left in a state of natural grass, and 
 were used chiefly as pasture land. They formed a 
 feeding ground for vast numbers of sheep, but they 
 are being brought by degrees under the dominion of 
 the plough, and on the highest of them you now find 
 fields of turnips and grain. The broad flat belts of 
 Oxford and Kimeridge clay that lie between the western 
 part of the Oolite and the base of the chalk escarp- 
 ment are still in great part used as pastures for cattle. 
 
 If we pass next into the Cretaceous series, which 
 in the middle and south of England forms extensive 
 tracts of country, we meet with many kinds of soil, 
 some, as those on the Lower Greensand, being ex- 
 cessively siliceous, and, in places, intermingled with a 
 marked proportion of oxide of iron. Such a soil still 
 remains in many places, intractable and barren. Thus 
 on the western borders of the Weald towards Petersfield, 
 where there is very little lime in the rocks, there are 
 wide-spread heaths on which you may walk for hours 
 
Wealden and Cretaceous Soils. 171 
 
 over ground unenclosed and almost as wild and refresh- 
 ing to the smoke-dried denizens of London as the 
 broad moors of Wales and the Highlands of Scotland. 
 These, partly from their height, but chiefly from the 
 poverty of the soil, have never been worth bringing 
 into a state of cultivation. Beneath these beds of Grreen- 
 sand lies the Weald clay, which is now almost entirely 
 cultivated and improved by help of deep drainage. 
 Below this Weald clay, various members of the Hastings 
 sand crop out, forming extensive tracts of country, all 
 belonging to the Wealden series, and forming in the 
 main the undulating hills that lie half-way between 
 the North and South Downs. The sand of these beds 
 is for the most part so fine that when dry it may be 
 described as an almost impalpable siliceous dust, and 
 within their area lay, and still lie in part, the old un- 
 cultivated forests of Ashdown, Tilgate, and St. Leonards. 
 Down to a comparatively late historical period, both 
 clays and sands were left in their native state, forming 
 those broad forests and furze-clad heaths that covered 
 almost the whole of the Wealden area. Hence the 
 name Weald or Wold (a woodland), a Saxon term, 
 applied to this part of England, though the word does 
 not now suggest its original meaning, unless to those 
 who happen to know something of German, or Saxon 
 derivatives. 
 
 The Chalk strata of the South Downs stretch far 
 
172 Chalk and Eocene Soils. 
 
 into the centre and west of England. South of the 
 valley of the Thames they form the North Downs, and 
 stretch north-east into Yorkshire in a broad unbroken 
 band. Most Londoners are familiar with these Downs, 
 lying, as they do, so near. In their wildest native state 
 where the ground lies high these districts were probably 
 almost bare of woods 'the bushless downs' and they 
 are still largely used for pasturage, yet here, also, culti- 
 vation is gradually encroaching. Broad sweeping plains, 
 even Salisbury Plain itself, which, within my own recol- 
 lection, were almost entirely devoted to sheep, are 
 being gradually invaded by the plough, and turned into 
 arable land. Many of the slopes of the great chalk 
 escarpments on the North and South Downs, in the 
 West of England, on the Chiltern hills and elsewhere, 
 are however so steep, that the ground, covered with 
 short turf, and in places dotted with yew and juniper, is 
 likely to remain for long unscarred by the ploughshare. 
 The clay bands of the Eocene beds, occur on all 
 sides of London. They are often covered by superficial 
 sand and gravel. Through the influence of the great 
 population centred here, originally owing to facilities 
 for inland communication afforded by the river ; this is 
 now, in great part, a highly cultivated territory. Here 
 and there, however, to the south-west, there are tracts 
 forming the lower part of the higher Eocene strata, 
 known as the Bagshot sands, which produce a soil 
 
Ice-drifted Soils. 173 
 
 so barren that, although not far from the metropolis, 
 it is only in scattered patches that they have been 
 brought within the influence of cultivation. They are 
 still for the most part bare heaths, and being sandy 
 or dry, we place camps upon them, and use them as 
 exercise-grounds for our soldiers. Higher still in this 
 Eocene series lie the fresh-water beds on which the 
 New -Forest stands, commonly supposed to have been 
 depopulated by the Conqueror and turned into a hunting 
 ground. But to the eye of the geologist it easily appears 
 that the wet and unkindly soil produced by the clays 
 and gravels of the district form a sufficient reason why 
 most of the hundred villages, said to have been de- 
 stroyed, perhaps never existed there, for the soil for 
 the most part is barren, and probably grew a great 
 native forest even in the Conqueror's day. 
 
 Such is a very imperfect sketch of the general 
 nature of the soils of Great Britain, and of their relation 
 to the underlying rocks. We have seen that through- 
 out large area<:, the character of the soil is directly and 
 powerfully influenced by that of the rock-masses lying 
 below. It must be borne in mind, however, that the 
 abrading agencies of the glacial period have done a great 
 deal towards commingling the detritus of the different 
 geological formations, and thus producing a wide-spread 
 drift of varied composition. This drift is, however, far 
 from being uniformly spread over the island. In some 
 
174 Races of Men. 
 
 districts it is absent, while in others it forms a thick 
 mantle, obscuring all the hard rocks and giving rise to 
 a soil sometimes nearly identical with that produced by 
 the waste of the underlying formation, and sometimes 
 of mixed clay and stones as in Holderness. Thus it is 
 often poor and often of the most fertile description, as 
 in certain upper members of the formation in the great 
 valley of the Lothians. 
 
 I shall now say a few words on the influence of the 
 geology upon the inhabitants of different parts of our 
 island. 
 
 Great Britain is inhabited by several great races, 
 more or less intermingled with one another. It re- 
 quires but a cursory examination to see that the more 
 mountainous and barren districts, as a whole, are in- 
 habited by two Celtic populations, very distinct from 
 each other, and yet akin, while the lowland parts are 
 occupied by the mixed descendants of various other 
 races. 
 
 From the earliest historical period it appears that 
 both sides of the English Channel were inhabited by 
 a Celtic people, known to us by the name of the Cimri 
 (Cymruj, ancient Britons, whom we now call Welsh. 
 Further north another Celtic people, the Gael, inhabited 
 the greater part of what is now termed Scotland, the 
 Isle of Man, and Ireland. Analyses of modern Welsh 
 and Gaelic prove, in the opinion of some accomplished 
 
Celtic Races. 175 
 
 scholars, that these Celtic branches, now so distinct, yet 
 sprung from the same original stock. Nevertheless I 
 believe that the Gael as a people is much more ancient 
 in our islands than the Cymru ; and I think it may be 
 proved, almost to demonstration, that the ancestors of 
 the Scottish Highlanders (who however are now largely 
 intermixed with Scandinavian blood) once spread not 
 only much farther south than the borders of the 
 Highlands, but that they even occupied the Lowlands 
 of Great Britain generally, for the names of many 
 of the rivers in England and even in Wales have a 
 Graelic and not a Welsh origin, complete or in combi- 
 nation. Thus, all the rivers called Ouse, the Usk, the 
 Esk, the Don, and others, derive their names from the 
 Gaelic. It is a characteristic of rivers often to retain 
 the names given them by a primitive race long after 
 that race has been expelled, and thus the Gaelic Uisge 
 (water) has not in all cases been replaced by the ancient 
 Welsh Gwy. This old Welsh word we constantly find 
 in a corrupt form, as in the Wye, the Medway, the 
 Tawe, the Towey, and the Teifi, the Dovey and the 
 Dove ; or the water of the rivers is expressed in another 
 form by the later dwfr or dwr as in Stour, Aberdour, &c. 
 In both languages, river (Avon) is the same. If 
 the earlier inhabitants were Graelic, then they were 
 driven northwards into their mountains, by the supe- 
 rior power of another and later Celtic population that 
 
ij6 Scandinavian Races. 
 
 found its way to our shores, and pushed onwards, oc- 
 cupying the more fertile districts of England and the 
 south of Scotland ; for the Gael would not willingly 
 have confined themselves to the barren mountains if 
 they could have retained a position on more fertile lands. 
 Thus I believe it happens that the north of Scotland, 
 beyond the great valley, is chiefly inhabited by the 
 Gael. On the east, however, along the coasts of the 
 Moray Firth, in Caithness and in the Orkney and Shet- 
 land Islands, the people are of Scandinavian origin and 
 speak Scotch, thus standing out in marked contrast 
 with the Gaelic clans, who possess the wilder and higher 
 grounds in the interior and western districts. There 
 is here a curious relation of the human population to 
 the geological character of the country. The Scandi- 
 navian element is strongly developed along the mari- 
 time tracts, which, being chiefly composed of Old red 
 sandstone, stretch away in long and fertile lowlands; 
 while the Celts are pretty closely restricted to the 
 higher and bleaker regions where the barren gneissic 
 and schistose rocks prevail. It is remarkable that a 
 number of the names of places in the centre and 
 south of Scotland are not Gaelic, but have been given 
 by the later race and can be translated by anyone who 
 has even a superficial knowledge of Welsh, and it is 
 almost certain that from the Lowlands of Scotland all 
 through the midland and southern parts of Britain, the 
 
Celts and Romans. 177 
 
 country was inhabited in the later Celtic times by the 
 same race that now peoples Cornwall and Wales. The 
 names of scores of places, now unintelligible to the 
 vulgar, proves it. Thus there are all the Coombs 
 (Gwm) of Devon and Somersetshire, and even as far 
 east as Croydon ; Dover (dwfr) ; the Cumbraes (Cymrii), 
 in the Clyde, and Cumberland ; and at Bath, by 
 the Avon, we have ' Dolly (dolau) meadows ; ' near 
 Birmingham 'the Lickey hills' (llechau); near Mac- 
 clesfield the rocky ridge called ' the Cerridge ' (cerrig} ; 
 and in the hills of Derbyshire ' Bull gap,' the Welsh 
 bwlch, translated, just as in another instance dolau 
 is repeated in the English word meadows. Again in 
 the lowlands of Scotland we have Aberdour (the mouth 
 of the water), Lanark (Llanerch, an open place in a 
 forest, or clearing), Blantyre (Blaen tir, a promontory 
 or projecting land), Penny cuik (Pen-y-gwig, the 
 head of the thicket), and many other corrupted Welsh 
 names. The wide area over which this language 
 was spoken is indeed proved by the ancient Welsh 
 literature, for the old heroic poem of the Grododin was 
 composed by Aneurin, said to have been a native of 
 Strath Clwyd in Scotland. But however this may be, 
 it is certain that the British Celts, when the Eomans 
 invaded our country, overspread the whole of the 
 southern part of Great Britain. By and by, they 
 mixed with their conquerors, but the Romans, as 
 
 N 
 
iy8 Celts and Saxons. 
 
 far as blood is concerned, seem to have played an 
 unimportant part in our country. They may have 
 intermarried to some extent with the natives, but 
 they occupied our country very much in the man- 
 ner that we now occupy India. Coming as military 
 colonists, they mostly went away as soon as their 
 time of service was up, and finally abandoned the 
 country altogether. But after the retirement of the 
 Romans, invasions took place by the Scandinavian 
 tribes, the Anglo-Saxons, and others who came to 
 occupy the land permanently. Then the native 
 tribes, dispossessed of their territories and driven west- 
 wards, retreated into the distant and mountainous parts 
 of the country, where the relics of this old Celtic 
 people are still extant in part of Devon and in Cornwall, 
 while among the Welsh mountains the same Celtic 
 element still forms a distinct and peculiar people. 
 There, till after the Norman conquest, they could still 
 hold out against the invader, and maintain their inde- 
 pendence in a region barren in the high ground, but 
 traversed by many a broad and pleasant valley. 
 Living, as the relics of the old Britons are apt to do, 
 so much in memories of the past, the slowly dying 
 language, and even the antique cadences of their re- 
 gretful music, speak of a people whose distinctive cha- 
 racters are waning and merging into a newer phase of 
 intellectual life. 
 
 It appears then that the oldest tribes now inhabiting 
 
Slate Quarries. 179 
 
 our country, both in Scotland and in the south, are to 
 be found among those most ancient of our geological 
 formations, the Silurian rocks, which, by old palaeozoic 
 disturbance^ form the high mountain lands, while the 
 lower and more fertile hills, the plains and table-lands, 
 are chiefly inhabited by the descendants of ( the heathen 
 of the northern sea,' who made good their places by the 
 sword after the departure of the Romans. 
 
 To enter in detail upon the peculiar effect of geology 
 on the industry of the various races or the populations 
 of different districts, would lead me far beyond the 
 proposed scope of these lectures. I shall, therefore, 
 only give a mere outline of what ought to be a course 
 of lectures, rather than by any means attempt to 
 exhaust the subject. 
 
 First, let us turn to the older rocks. In Wales these 
 consist, as I have already stated, to a great extent of 
 slaty material. The largest slate quarries in the world 
 lie in the Cambrian rocks of Carnarvonshire. One 
 single quarry, that of Penrhyn, is half a mile in 
 length, and more than a quarter of a mile from side to 
 side. A number of other quarries occur in the same 
 district, but none of them of the same vast size. Some 
 other important quarries also lie in the Lower 
 Silurian rocks near Ffestiniog in Merionethshire. In 
 these districts there is a large population which is 
 
 N 2 
 
i8o Slate Quarries. 
 
 chiefly supported by the quarrying and manufacture 
 of slates. The slate quarry at Penrhyn, near Bangor, 
 presents a wonderful spectacle of industry. More than 
 3,000 men are there employed solely in the making 
 of slates, which are exported to all parts of the world, 
 and yield a vast revenue to the proprietor, the Hon. 
 Colonel Douglas Pennant. Other quarries at Llanberis, 
 which belonged to the late Mr. Assheton Smith, employ 
 nearly an equal number of men in comfort, and the 
 revenues to the proprietor are proportionate. There 
 are many other smaller quarries in the neighbourhood, 
 while further south in Merionethshire some are worked 
 in caverns instead of open day. So great is the profit 
 derived from slate quarries that every here and there 
 in Wales, where the rocks are more or less cleaved, 
 speculators go to work and opening part of a hill- side, 
 find a quantity of rotten stuff, or of slate full of iron 
 pyrites, or cut up by small joints, or imperfectly cleaved, 
 and after a time being ruined, they sell the property 
 to other speculators, who ruin themselves in turn. 
 There are slate quarries in South Wales, Cumber- 
 land, and in some parts of Scotland, but they are all un- 
 important compared with the immense quarries of 
 North Wales. 
 
 In various districts of Great Britain the rocks abound 
 in the ores of certain metals, and, occurring in part in 
 hilly pastoral regions, the workers in these mines are 
 
Ores. 181 
 
 rarely congregated in great crowds like the slate quar- 
 riers of North Wales, or the miners of coal and iron. 
 I will first allude to the cases in which the mineral 
 wealth is derived from what are termed lodes, from 
 whence are derived our chief supplies of copper, tin, 
 zinc, and lead. It is worthy of remark that these lodes 
 are almost wholly confined to our oldest or palaeozoic 
 rocks. The Devonian formation contains them in Devon 
 and Cornwall, and the Silurian formations in Wales, 
 Cumberland, in the hills of the south of Scotland, and 
 here and there throughout the Highlands. In th6 
 Carboniferous limestone they are also found in North 
 Wales, Cumberland, and Derbyshire. The chief districts 
 in England where copper and tin are found are in Devon 
 and Cornwall; and in Wales, especially in Cardigan- 
 shire and Montgomeryshire, there are ores of copper, and 
 many lodes highly productive in ores of lead, some of 
 which are rich in silver. No tin mines occur in that 
 district. Gold also has of late years been found in 
 Merionethshire between Dolgelli, Barmouth, and Ffes- 
 tiniog, sometimes as at Clogau, in profitable quantity, 
 but generally only in sufficient amount to form pretexts 
 for getting up companies which sometimes lure unwary 
 speculators to their loss. This Welsh gold is found in 
 lodes near the base of the Lingula flags, which in that 
 area are talcose, and pierced by eruptive bosses of 
 igneous rocks and greenstone dykes. 
 
1 82 Ores. 
 
 In older times extensive gold mines were worked 
 in Caermarthenshire at the Grogofau (ogofau, caves), 
 between Llandovery and Lampeter. These excavations 
 were first made open to the day, in numerous irregular 
 shallow caverns where the gold-bearing quartz veins 
 were followed into the hill; and later by means of 
 lofty well-made galleries, which cut the lodes deeper 
 underneath. The gold was also found in washings of 
 the superficial gravel of nearly a mile in length on the 
 banks of the river Cothy. The galleries and the wash- 
 ings are clearly Koman, but it has been surmised by 
 the proprietor Mr. Johnes that the ruder caverns partly 
 date from more ancient British times. The huge exca- 
 vations must have made ugly scars on the hills in the 
 day when they were worked, but time has healed them. 
 The heaps of rubbish are now green knolls, and gnarled 
 oaks and ivy mantle the old quarryings. 
 
 In the Carboniferous limestone districts, both of 
 North Wales and Derbyshire, there are numerous lead 
 mines ; and, as I have already said, it occurs in the 
 underlying Silurian strata, as in South Wales and also 
 in the Lead Hills in the south of Scotland, where lead 
 associated with silver, and even a little gold, has long 
 been worked. There are numerous veins of lead and 
 other ores in the limestone of the Mendip Hills. 
 
 I must now endeavour to give you an idea of what 
 a lode is. A lode is simply a crack, more or less 
 
Theories of Lodes. 183 
 
 filled with various kinds of mineral matter, such as 
 layers and nests of quartz, carbonate of lime, carbo- 
 nate of copper, sulphuret of copper, sulphuret of lead, 
 oxide of tin, or with other kinds of ore. Various 
 theories have been formed to account for the presence 
 of ores in these cracks, and to this day the subject is 
 not perfectly clear. Formerly, the favourite hypothesis 
 was, that they were formed by a sublimation from 
 below, somehow or other connected with the internal 
 heat of the earth ; and the ores were supposed to have 
 been deposited in the cracks through which the heated 
 vapours passed. A great deal also has been said on the 
 effect of electric currents passing through the rocks, and 
 aiding in depositing along the sides of fissures the 
 minerals which were being carried up by sublimation 
 from below, or were in solution in waters that found 
 their way into the fissures. I dare not utter any posi- 
 tive statement on the question, but my opinion is 
 that the ores of metals in lodes have generally been 
 deposited from solutions. We know that water, espe- 
 cially when warm, can take up silica in solution and 
 deposit it, as in the case of the Greysers in Iceland ; and 
 we also know that metals may, in some states, be held 
 in solution in water, both warm and cold. This is 
 proved by the accurate results of chemists, who have 
 detected silver and gold, and, it is said, copper, in 
 solution in sea water. We must remember that, when 
 
184 'Theories of Lodes. 
 
 the lodes or cracks were originally formed, those parts 
 of them that we explore were not so near the surface as 
 we now see them ; but in a great many, and perhaps in 
 all cases, they lay deep beneath the surface, covered by 
 thousands of feet of rock that have since been removed 
 by denudation. They were therefore probably, in all 
 cases, channels for subterranean waters, both in their 
 upper portions that have been removed by denudation 
 and in the originally deeper parts that now remain. It 
 is not unlikely also that these subterranean waters may 
 often have been warm, seeing that they sometimes lay 
 deep in the interior of the earth and came within the 
 influence of the so-called central heat, whatever may be 
 its origin. For my own part I do not doubt that the 
 ores which we meet with in these cracks or lodes were 
 formed by infiltration, for strings of copper, lead, and 
 tin, for example, occur in the mass just in the same 
 way that we find mixed with them strings of carbonate 
 of lime or quartz. If this be so, then, just as the lime 
 and silica may have been derived from the percolation 
 of water through the rocks that form the country on 
 each side of the lode, so the metalliferous deposits seem 
 to have been derived from metalliferous matter minutely 
 disseminated through the neighbouring formations. We 
 are, however, still in the dark as to many of the condi- 
 tions under which the process was carried on. 
 
 Ores of iron are common in lodes and in hollows or 
 
Coal and Iron. 185 
 
 pockets, both in the limestones of the Devonian and 
 Carboniferous periods. 
 
 In the Coal-measures, however, we have our greatest 
 sources of mineral wealth, because they have been the 
 means of developing other kinds of industry besides 
 that which immediately arises from the discovery of the 
 minerals which the Coal-measures contain. In the great 
 coal-fields of this formation occur all the beds of coal 
 worth working in Britain. In the South Wales coal- 
 field there are more than 100 beds of coal, great and 
 small, and one celebrated bed in South Staffordshire 
 attains a thickness of 40 feet. By a fortunate geologi- 
 cal coincidence, from the very same Carboniferous 
 strata for nearly 100 years past we have obtained 
 almost all the iron that has been employed in our 
 manufactures. Of late years, however, a great deal of 
 valuable iron ore has been obtained from the Marlstone 
 of Yorkshire, and the Northampton sands which are 
 the geological equivalents of the Stonesfield slate. 
 In older times, in the Weald of the south of England, a 
 considerable amount of iron used to be mined and smelted 
 with wood or charcoal, before the Coal-measures were 
 worked extensively, and when the Weald was covered 
 to a great extent with forest. Then the chief part of our 
 iron manufactures was carried on in the south-east of 
 England. Indeed, late in the last century, there were 
 still iron furnaces in the Weald of Kent and Sussex. 
 
1 86 Coal- Fields. 
 
 The last furnace is said to have been at Ashburnham, 
 and every here and there you may now see heaps of slags 
 overgrown with grass, and the old dams which supplied 
 the water that drove the water-wheels that worked the 
 forges of Kent and Sussex. It is said that, the cannon 
 that were used in the fight with the Spanish Armada 
 came from this district ; and the rails round St. Paul's 
 were also forged from the Wealden iron. 
 
 Besides coal and iron, the Coal-measures yield quan- 
 tities of clays, which are of considerable value. The 
 chief of these is fire-clay, which is used so largely in 
 the manufacture of crucibles, fire-bricks, and furnaces. 
 But by far the most important mineral which this geo- 
 logical formation affords is ' coal. Instead of occur- 
 ring in veins and lodes, as many of the metals do, 
 it is spread out in vast sheets, or layers, bed above bed, 
 within the crust of the earth. If you look at the geolo- 
 gical map of England, you will see that large patches 
 are coloured black they are the Coal-measure districts 
 of Great Britain. Some of these coal-fields, as, for in- 
 stance, the great coal-field of South Wales and the 
 Forest of Dean, lie in a basin-shaped form, and the coal 
 crops to the surface all round the basin. But in other 
 parts of England the coal does not occur in basins, but 
 crops to the surface at one side alone, the remainder 
 being shrouded by deep coverings of New red sand- 
 stone, and of other Secondary rocks. Thus it some- 
 
Coal-Fields and Faults. 187 
 
 times happens that only by a series of geological 
 accidents have the Coal-measures been brought to the 
 surface, exposed to view, and rendered available for use. 
 We may take the South Staffordshire coal-field as an 
 example, where the New red sandstone and Permian 
 rocks are thrown down against the coal-field on both 
 sides. Originally, before these faults took place, the New 
 red sandstone and other rocks spread entirely over the 
 surface. The New red sandstone and marl, where 
 thickest, are more than 2,000 feet thick ; above it lies 
 the Lias, 900 to 1,500 feet thick ; then come the Oolites, 
 and lastly all the Cretaceous strata. This enormous 
 mass of superincumbent strata once lying above the 
 south Staffordshire coal-measures was afterwards dis- 
 located by faults, which brought the lower portions of 
 them down against the sides of the present coal-field. 
 A vast denudation must have ensued, whereby a great 
 thickness of the formations nearest the surface was re- 
 moved, and the whole country was worn down to one 
 comparatively general level. It is by such processes 
 that some of our large and productive coal-fields have 
 been exposed at the surface. Hence we now find a great 
 manufacturing population all centred in areas (like those 
 of South Staffordshire, Warwickshire, and Ashby-de-la- 
 Zouch), which might never have been known to contain 
 coal-fields, had it not been for the geological accidents 
 of those faults and denudations which I have repeatedly 
 
1 88 Coal-Fields and Population. 
 
 noticed and explained. In other cases, as in the great 
 South Wales coal-field, that of the Forest of Dean, 
 and the coal-field of the great central valley of Scotland 
 through which the Clyde and the Forth run, the Car- 
 boniferous strata were probably never covered by Se- 
 condary strata. Between the mouth of the Firth of 
 Clyde and the mouth of the Firth of Forth the whole 
 country is one great coal-field, and this is the part of 
 Scotland where the population is thickest. Bordering 
 Wales and the mountains of Lancashire and Derbyshire, 
 on the east and west, are three great coal-fields, and 
 these districts also contain dense populations. Further 
 north lies the great Newcastle coal-field, where, again, 
 the population is proportionately redundant. All the 
 central part of England, which is dotted over with coal- 
 fields, teems in like manner with inhabitants. The 
 South Wales coal-field, which is the largest of all, how- 
 ever, does not, except in places such as Swansea and 
 Llanelly, show the same concentration of population. 
 This exception is due to peculiar circumstances. A 
 great part of this area being exceedingly hilly, the coal 
 has been heretofore by no means worked to the same 
 extent as in the coal-fields of the middle and northern 
 parts of England, which have been extensively mined 
 for a longer period. 
 
 I have already remarked that a large part of the 
 wealth which we owe to our Carboniferous minerals, 
 
Coal- Fields and Manufactures. 189 
 
 arises, not so much from the commercial value of these 
 minerals themselves, as from the fact that they form the 
 means of working many different branches of our in- 
 dustry. To the vast power which steam has given us, very 
 much of our extraordinary prosperity as a nation is due. 
 Yet were it not for our coal-beds, the agency of steam 
 would be almost wholly denied to us. And hence it is 
 that our great manufacturing districts have sprung up 
 in the vicinity of coal-fields. There iron furnaces 
 glare and blow day and night, there are carried on 
 vast manufactures in all kinds of metal, and there 
 our textile fabrics are chiefly made. In these busy 
 scenes a large part of the population of our island finds 
 employment, and thence we send to the farthest parts 
 of the earth those endless commodities, which, while 
 they have supplied the wants of other countries, have 
 given rise in large measure to the wealth and commerce 
 of our own. 
 
 There are some other geological formations which 
 afford materials for manufactures. Thus, in the south- 
 west of England, in the granitic districts of Devon and 
 Cornwall, and a little further east in Dorsetshire, near 
 Poole a great proportion of the finer kinds of clays 
 occur, which are used in making stoneware and porce- 
 lain. In Devon and Cornwall the decomposition of 
 granite affords the substance known by the name of 
 Kaolin, from which all the finer porcelain clays of our 
 
190 Porcelain Clay. 
 
 country are made. It is formed by the disintegration 
 of the felspar of granite. This felspar, as I showed in 
 a previous lecture, consists of silicates of alumina, and 
 soda or potash. The soda and potash are comparatively 
 easily dissolved, chiefly through the influence of car- 
 bonic acid in the water that falls upon the surface ; and 
 the result is that the granite decomposes to a con- 
 siderable depth. In some cases I have seen granite 
 which had never been disturbed by the hand of man, 
 which for a depth of twenty feet or more might be 
 easily dug out with a shovel. Owing to this decom- 
 position, a portion of the felspar passes into kaolin, 
 which is washed down by the rains into the lower levels, 
 where, more or less mixed with quartz, and the other 
 ingredients of granite, it forms natural beds of com- 
 paratively pure clay. This is dug out, and the clay is 
 transported chiefly to the district of the Potteries in 
 North Staffordshire. The same process is sometimes 
 secured by art, when the decomposed granite being dug 
 out, is washed by artificial processes, and the more 
 aluminous matter is separated from the quartz with 
 which it was originally associated. Then, in the Pot- 
 teries, it is turned into all sorts of vessels fine por- 
 celain, stone-ware, and common-ware, in every variety 
 of size, and form, and texture. 
 
 In the Eocene tertiary beds in the neighbourhood of 
 
Clay and Flints. 191 
 
 Poole, there are large lenticular beds of pipe-clay, in- 
 terstratified with the Bagshot sand. Great quantities 
 of this clay are exported into the Pottery districts to be 
 made into the coarser kind of earthenware, and they 
 are also mixed with the finer materials from Devon and 
 Cornwall, to make intermediate qualities of stone-ware 
 and china. 
 
 But in addition to clay, the chalk is brought into 
 requisition to furnish its quota of material for this 
 manufacture. The flints that are found embedded in 
 the chalk, chiefly in layers, are also transported to the 
 Potteries, and ground up with the aluminous portions 
 of the clay, since it is necessary to use a certain pro- 
 portion of silica in the manufacture of porcelain. 
 
 Many other formations, such as the Old and New 
 red marls, are also of use when clay is required. The 
 Oolitic and Liassic strata are to a great extent com- 
 posed of clay, such as Lias clay, Fuller's earth, Oxford 
 and Kimeridge clay, and the Grault lies in the middle 
 of the Cretaceous strata. An abundance of material is 
 found in these formations for the manufacture of bricks, 
 earthenware pipes, and so on ; and it is interesting to 
 observe how in this respect the architecture of the 
 country is apt to vary according to the nature of the 
 strata of given areas. In Scotland and the north of 
 England, where hewable stone abounds, almost all the 
 
192 Jet, Glass, Sand, 6fc. 
 
 houses are built of sandstone, grey and sombre ; in 
 many of the Oolitic districts they are of limestone, and 
 lighter and more graceful ; while on the Lias and in 
 the Woodland area of the Weald we have still the relics 
 of an elder England in those brick and timbered houses 
 that speak of habits and manners gone by. 
 
 In the Lias strata, chiefly in the upper Lias clay 
 in Yorkshire, beds of lignite and jet are found near 
 Whitby, which, however, do not form anything like 
 an important branch of manufacture. 
 
 The glass-sand used in this country is chiefly derived 
 from the Eocene beds of the Isle of Wight, and from 
 the sand-dunes on the borders of the Bristol Channel. 
 In the Isle of Wight, the sandy strata lie above the 
 London clay, and are the equivalent of part of the 
 Bagshot sands. They are remarkably pure in quality, 
 being formed of fine siliceous white sand. These sands 
 are largely dug and exported to be used in glass-houses 
 in various parts of the country, as in Birmingham and 
 elsewhere. 
 
 A large proportion of the cement stones of our 
 country comes from the Lias limestone. These lime- 
 stones are not pure carbonate of lime, but are formed 
 of an intermixture of carbonate of lime and aluminous 
 matter. It is found by experience that the lime from 
 this kind of limestone is peculiarly adapted for setting 
 under water. Hence the Lias limestone has always been 
 
Building- Stones. 193 
 
 largely employed in the building of piers and other 
 structures that require to be constructed under water. 
 Cement stones are also found to some extent in the 
 Eocene strata, and are obtained from nodules dredged 
 from the sea-bottom at Harwich, and the south of Eng- 
 land. These are transported hither and thither, to be 
 used as occasion may require. 
 
 The chief building stones of our country, of a hewable 
 kind, are the limestones of the Oolitic rocks, the Mag- 
 nesian limestone, the Carboniferous limestone, and the 
 Carboniferous sandstones. The chief Oolitic building 
 stones are from the Isle of Portland and the Bath 
 Oolite. St. Paul's was built of Portland stone, and the 
 mmense quantities of rejected stones in the old quar- 
 ries, show how careful Sir Christopher Wren was in the 
 selection of material. The Carboniferous sandstones in 
 Lancashire, and in the neighbourhood of Leeds, Edin- 
 burgh, and Glasgow afford a large quantity of admirable 
 building material, which has been used almost exclu- 
 sively in the building of these towns. Some of it is 
 exceedingly white, it is easily cut by the chisel, and 
 may be obtained in blocks of immense size. But in 
 some of the beds there is so much diffused iron, not 
 visible at first sight, that in the course of time this, 
 as it oxidises, forms dark stains which discolour the 
 exterior of the buildings. The New red sandstone also 
 yields its share of building stones, but much of it is 
 
 o 
 
1 94 Building- Stones. 
 
 very soft and easily worn by the weather, a notable 
 example of which may be seen in the cathedral of 
 Chester. The white Keuper sandstone of Grinshill, 
 north of Shrewsbury and elsewhere, is an excellent 
 stone. The Old red sandstone is also used as a building 
 stone in its own area, and the Caradoc sandstone of 
 Shropshire yields a beautiful white material. 
 
 In Devonshire and Cornwall, and in Scotland, but 
 chiefly near Aberdeen, the granite quarries afford much 
 occupation to a number of people. Now that it has 
 become the fashion to polish granites, these rocks are 
 becoming of still more importance. But as they are 
 not so easily hewed as sandstone, they do not come 
 into use as ordinary building stones, except in such 
 districts as Aberdeen, where no other good kind of rock 
 is to be had. In England the Magnesian limestone is 
 extensively quarried for building purposes. It is of very 
 various qualities, sometimes exceedingly durable, re- 
 sisting the effects of time and weather, and in other 
 cases decomposing with considerable rapidity. In dis- 
 tricts where it occurs, there are churches, and castles, 
 such as Conisbro', built of it, wherein the edges of the 
 stones are as sharp as if fresh from the mason's hands. 
 You can see the very chisel marks of the men who 
 built the castle, in days soon after the time of William 
 the Conqueror. The Carboniferous Limestone also is 
 an exceedingly durable stone. The Menai bridges were 
 
Summary. 195 
 
 built of it. In Caernarvon castle the preservation of 
 this limestone is well shown. The castle is built of 
 layers of limestone and sandstone, the sandstone having 
 been chiefly derived from the millstone grit, and the 
 limestone from quarries in Anglesey, and on the shores 
 of the Menai Straits. The limestone has best stood 
 the weather. Sandstone, though durable, is rarely so 
 good as certain limestones, which being somewhat 
 crystalline, and formed to a great extent of Encrinites, 
 also essentially crystalline in structure, have withstood 
 the effect of time. 
 
 I have now attempted to give you an idea of the 
 general physical geography of our country, as depen- 
 dent on its geology. I first described to you the 
 classification of rocks. I divided them into two classes, 
 and one sub-class ; consisting of aqueous rocks formed 
 by the action of water, igneous rocks by the action of 
 heat ; and of metamorphic rocks which were originally 
 stratified, but have since been acted on by heat and 
 other influences. I then showed you the distribution 
 of these rocks over our country. They have been 
 affected by disturbances and denudations so that where 
 most disturbed, and hardened, and denuded, there we 
 have mountainous districts ; for the greater prominence 
 and ruggedness of surface of these regions arises partly 
 from the hardness of the rocks, partly from the extreme 
 denudation which they have undergone. The Se- 
 
 o 2 
 
196 Summary. 
 
 condary and Tertiary rocks not being so much dis- 
 turbed, and being younger, have never been so much 
 denuded, and therefore form plains and table-lands. 
 Moreover we saw that over all these surfaces, in ad- 
 dition to the vast amount of erosion which must have 
 been effected in Palaeozoic, Secondary and older Tertiary 
 times, renewed denudations accompanied by great cold 
 occurred at a late Tertiary epoch. The result of the 
 last abrasion has been to cover the surface more or less 
 with loose superficial detritus, upon which part of the 
 fertility of portions of the country, and the peculiarity 
 of some of its soils depend. We then passed on to 
 notice what I considered to be a very remarkable result 
 of this last great denudation brought about under the 
 influence of ice, by which the chief part (I by no means 
 say all) but by which the chief part of the lakes of our 
 country have been formed; and not of our country 
 alone, but of a large part of the northern hemisphere. 
 It is a remarkable thing, indeed, to consider, if true 
 and I firmly believe it to be true, that most of those 
 great hollows in which our lakes lie, have been scooped 
 out by the slow and long-continued passage of great 
 sheets of glacier ice, quite comparable to those vast 
 masses that cover the extreme northern and southern 
 regions of the world at this day. The water drainage 
 of the country is likewise seen to be dependent on 
 geological structure. Our large rivers chiefly drain to 
 
Summary. 197 
 
 the east, the smaller ones to the west, because the 
 great axes of disturbance happened to lie nearer our 
 western than our eastern coasts. Again, the quality of 
 water in these rivers depends, as we have seen, on the 
 nature of the rocks through which they flow, and of the 
 springs by which they are supplied. 
 
 Then, when we come to consider the nature of the 
 population inhabiting our island, we find it also to be 
 greatly influenced by this old geology. The earlier 
 tribes have been driven into the more barren mountain 
 regions in the north and west, and so remain to this 
 day still speaking original languages, but gradually 
 melting up with the great masses of mixed races that 
 came in with later waves of conquest from other parts 
 of Europe. These later races settling down in the more 
 fertile parts of the country, first destroyed and then 
 again began to develop its agricultural resources. In 
 later times they have applied themselves. with wonderful 
 energy to turn to use the vast stores of mineral wealth 
 which lie in the central districts. Hence have arisen 
 those densely peopled towns and villages where the 
 manufactures of the country are carried on. Yet in the 
 west, too in Devon and Cornwall, and in Wales, where 
 some of the great metalliferous and the slaty regions 
 lie there are busy centres of population, where the 
 mineral products are worked by the original Celtic 
 inhabitants. 
 
198 Summary. 
 
 It is interesting to go back a little and enquire what 
 may have been the condition of our country when man 
 first set foot upon its surface. We know that these 
 islands of ours have been frequently united to the Con- 
 tinent, and as frequently disunited, partly by elevations 
 and depressions of the land, and to a great extent, also, 
 ,by denudations. When the earliest human population 
 came, Britain was probably united to the Continent by 
 great plains of boulder-drift. Such is the deliberate 
 opinion of some of our best geologists, and also that 
 these prehistoric men inhabited our country along with 
 the great hairy Mammoth, the Ehinoceros, the Cave 
 Bear, the Lion, and the Hippopotamus, and perhaps 
 travelled westwards from the Continent of Europe, along 
 with these extinct mammalia. But in later times, de- 
 nudations and alterations of level having again taken 
 place, our island became again disunited from the 
 mainland. And now, with all its numerous firths and 
 inlets, its great extent of coast, its admirable harbours, 
 our country lies within the direct influence of that 
 Gulf stream which softens the whole climate of the 
 west of Europe, and we, a people of mixed race, Celt, 
 Scandinavian, Saxon, Norman, more or less inter- 
 mingled in blood, are so happily placed that, in a great 
 measure, we have the command of the commerce of 
 the world, and send out fleets of merchandise from 
 every port. And we are happy, in my opinion, above 
 
Summary. 199 
 
 all things in this, that .by an old denudation we have 
 been dissevered from the Continent of Europe ; for 
 thus it happens that, free from the immediate contact 
 of hostile countries, and almost unbiassed by the in- 
 fluence of peoples of foreign blood, during the long 
 course of years in which our country has never seen 
 the foot of an invader,* we have been enabled so to 
 develop our own ideas of right and wrong, of religion, 
 of political freedom, and of political morality, that we 
 now stand one of the freest countries on the face of 
 the globe, enjoying our privileges under the strongest 
 and freest government in the living world. 
 
 * The miserable French descents in Pembrokeshire and Ireland do 
 not deserve the name of invasions. 
 
 THE END. 
 
 lOTTDOW 
 
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