O* VALLRYS. 



of a waterspout (High Pike, in Cumberland) [WATERSPOUT], or the 

 intumescence of a wet peat-bog (above Krighley, Yorkshire). Front 

 and the sun's heat are felt in extreme in the high region* which give 

 birth to riven, and by their alternation the rock are broken and 

 disintegrated. To then regioni Hutton and I'lay fair rightly propoee 

 to carry their pupil* for the purpose of impressing upon their minds 

 the extensive waste produced on the earth's surface by modern causes 

 in action. Examples -are everywhere abundant: Glen Coe, Burrow- 

 dale, Snowdonia, may be cited. (N.B. The yauntl features of the 

 higher parU of mountain-valleys are nearly the same around glaciers, 

 and these features are liable to change by the violent alternations of 

 temperature.) 



B. The second stage of valleys is that which admits of the union of 

 permanent natural springs to the occasional hill-side floods, and of the 

 gathering of these streamlets into a rapid and agitated river. The now 

 augmented water is often confined in a narrower glen than any of its 

 tributaries, and rushes and cascades among rocks and mounds, which 

 are so disposed as to show proof that the course of the stream has 

 varied from time to tune, as the levels changed, in consequence of 

 eroding action. 



C. At length the glen opens in a pebbly plain, or sinks into a brood 

 and quiet lake. Such liken, or plains which seem to have been lakes, 

 are of very general occurrence along the line of rivers, while they are 

 engaged in the midst of their parent mountains (Derwent Water, 

 Llanberis, Loch Tay). They even appear at the foot of particular 

 mountains, receiving only occasional streams (Red Tarn, under Hel- 

 Tcllyn), and in a very great variety of cases appear to be irregular 

 hollows left after great disturbances of the stratification amongst the 

 angularly posited masses of broken ground. Their depth is from a 

 few feet to a thousand feet (Lake of Geneva) below the level of the 

 valley ; and as the rivers which enter the upper ends there lose their 

 force in the expansion of water, and drop their transported sediments, 

 thejp-owCA of Hew lad in that part of such lakes is proportioned to, 

 and is in truth a measure of, the whole effects of those rivers in trans- 

 porting away the detritus of the mountains round their source. Such 

 lakes then are natural dynamometer*, which may with proper caution 

 be used to determine the amount of transported materials delivered 

 into them in given times by rivers ; they also give the sum of all the 

 effects of this kind performed by such rivers ; and thus finally they are 

 a/ro/ ckronomttert ; for by dividing, in any particular case, the 

 integral effect or mass of deposited materials by the rate of annual 

 progress, an approximate answer in years is given to the question of 

 the length of time which has elapsed since that river began to How. 

 By this argument De Luc arrived at the conclusion that the desicca- 

 tion of our continents by elevation above the sea is a phenomenon of 

 no very great antiquity, belonging to an epoch only a few thousand 

 years removed from our own. Though geologists cannot, from the 

 evidence of particular lakes in certain districts, adopt this conclusion 

 for other districts where quite different phenomena appear, Professor 

 Sedgwick and other eminent persons have declared the argument of 

 L>e Luc, within its proper limits, to be unanswered and unanswerable. 

 In all canes then where lakes are so interposed in the path of a river 

 that they must be believed to have received all the sediments which 

 that river has brought, the cubic volume of these accumulations hi 

 the lake may be compared with the cubic space of the concavities 

 between the hills along the line of the rivers and rivulets above the 

 hike ; and if found to be inferior in a noteable degree, we may posi- 

 tively conclude that these concavities have not been produced, though 

 doubtless they have been enlarged and modified, by the atmospheric 

 agencies belonging to that particular area of drainage. Now this com- 

 parison has been often mode, and generally with the positive result, 

 that the excavation of the valleys above the lakes is not the effect of 

 those watery agencies now exerted within them. Excavated however 

 some of them have been by watery agency, and in all of them the 

 surface slopes have been adjusted by this power, both in level and in 

 direction, to the boundaries of the present lake ; but we must avoid 

 the error of assuming that no other currents having a different origin 

 may have operated in those valleys before the existence of the lakes. 



L. Beyond the region of the lake*, the rivers, flowing away from the 

 rugged mountains, encounter ranges of stratified rocks, often very 

 regularly inclined at a moderate angle, in parallel ridges and hollows 

 which correspond to alternately hard and soft portions of the series of 

 strata. If there were no gaps across these ridges, so as to connect 

 their intervening hollows, each of these hollows would include one or 

 many lakes, and the river whose course we are tracing could not pass 

 over the first of the ridge* until the hollow ipace between it and the 

 lake district (C) was filled with water, generally at a high K . 

 such a circumstance were supposed ever to have happened, the water* 

 might be imagined to make themselves a passage across this ridge, and, 

 by like reasoning, across any lower ridges lying beyond. (See the 

 figure* above, and in art. OEOLOOT, in NAT. HIST. Div.) 



It sometimes happens that more than one group of such parallel 

 ridges and hollows as the mountain limestone group (I), followed by 

 the <*,litic ridge* (o), or those by the chalk-hills ) lie on the course 

 of even one river, and require the repetition of such phenomena to 

 account fur the course of the valley. But a greater difficulty must be 

 encountered. The very hollow* themselves in which these sheets of 

 water are imagined to bare spread are valleys, and yield a* plain proof 



VALLEYS. 



uo 



that they also have been excavated and modified by watery action, as 



the river-channels which cross them. Kor in the midst of such hollows, 



insulated hills (the unrenioved jwrtions of the same or the nearest 



cuporjacent strata) remain variously distributed, to mark the ai 



height of the laud therein, and attest the enormous degra 



ha* been there occasioned. If, then, the supposed lake g\<- il. 



to break over and cut through the inclosing barrier of rock beyond, so 



a* to shape a course and descent to the river, the excav 



space in which the hike was gathered was the fruit of earlier and 



different watery action. This conclusion is again and again i 



upon our attention as we proceed along the line of the valley. 



K. In crossing through the parallel ridges and hollows of hard and 

 soft strata, the river is confined to steep, narrow, angularly bent 

 passages among the hard rocks ; but in the softer strata between them 

 it flows and winds more at liberty, through wider spaces, which open 

 far on each side, and bring additional supplies of water. In these 

 hollows the velocity of the stream dies away, and the sediments derived 

 from wasting of the adjoining high grounds fall on fertile meadows in 

 floods or silt up their own channels in times of slack-water, while 

 around appear insulated bills, left by the ancient water-currents which 

 swept away the materials around them. 



F. The river, on emerging from thcue ranges of secondary strata, 

 enters a wide region of plains and low hills of gravel (y), rising irregu- 

 larly amidst alluvial plains and marshes (m), amongst which, for a 

 certain distance, the tide flows up the expanded river-channel. 



Wherever these marshy plains and gravelly ridges are locally i 

 by geographical situation and distribution to the main stream or 

 smaller branches, so as to allow of the possibility of referring their 

 formation to the action of the existing fluviatile and tidal currents, it ' 

 would be false philosophy to look for a more remote or more general 

 cause. This is often the case, perhaps generally so, with the alluvial 

 sediments, for they contain often fi> il and other marks of 



limited lacustrine or fluviatile action ; but it is seldom the ca.- 

 the gravel beds and ridges. These often lie across the path of the 

 river (ee), and ofU-r. il t a great height above it; often consist of 

 stones not only beyond the present power of the river to transport, but 

 such as do not occur in titu in any part of the area drained by iU main 

 stream or tributary waters. 



Vet, from their form, distribution, and composition, there is no 

 doubt that some have lum wholly accumulated and all modified by 

 water-currents ; so that hero again we hare proof of the waste and 

 remodelling of the surface of the earth by other forces than the existing 

 atmospheric agencies. 



G. On reaching the sea, we find the influence of the river prolonged 

 into the salt-water, augmenting the mass of sediments drifted coast- 

 wise by the tide, and feebly assisting in the distribution ..)' UK-HI. But 

 the bed of the sea is unequal, soft, or rocky, excavated into 1>< 



and varied by sand- banks and gravel-beds, not unlike those on tin- 

 neighbouring land, and even yielding, as they do, bones of gigantic 

 extinct mammalia (Happisburgh coast [and in fact the eastern coast of 

 England from Bridlington to beyond the mouth of the Thames] ). 

 These points of agreement between the actual sea-bed and the neigh- 

 bouring lands mark some community of origin : the laud has been 

 raised out of the sea, and owes some of its irregularities to marine 

 currents (as Buffon thought), or the sea's bed is subsided land. Each of 

 these may be partially and locally true, but there can be no doubt of 

 the sea-currents having power to alter the distribution of sand-banks 

 and gravel-banks to some considerable, though not precisely known, 

 depth ; and as all the stratified crust of the earth has been once the 

 bed of the sea, it is evident that the action of marine currents is a 

 cause of universal application to the theory of the inequalities of the 

 earth's surface, as well as of extraordinary power. 



The slight sketch here presented includes phenomena which may be 

 seen on the English rivers, though not all on one and the same stream : 

 the description may be verified in every one of its stages a hundred 

 times, and augmented with additional phenomena by any intelligent 

 reader personally acquainted with the phycicol geography of Britain. 

 Exactly similar phenomena, either all in the same order or variously 

 associated, may be paralleled by instances selected from other parts of 

 the world, and it only remains to apply a plain course of reasoning 

 to them. 



The action of atmospheric agencies, river-streamlets, and rivers, 

 with or without lakes, with or without glaciers, is always one and the 

 same : to degrade the high lands and to raise the low, and thus to 

 equalise the levels, and to diminish the irregularities of the surface of 

 the globe ; and this because of the universal action of gravity, wher- 

 ever there are weighty masses and inequality of level. The sea's 

 action is similar, and 'though complicated by tidal fluctuations, a* 

 rivers and lakes are by drought and inundations, and by the variable 

 influence of wind and temperature, its final results are of the same 

 character. 



This is indisputable. It is equally true that the direction of the 

 existing watery agencies on the land is determined by the present 

 relation of levels between the different parts of the land, and between 

 the land and the sea. Moreover the effects of these agencies are perfectly 

 adjusted to these levels. It follows inevitably that the sum of the 

 effects of these existing agencies has been to diminish the original 

 inequalities of the earth's surface, that is to say, to lower the hills, to 



