VALLEYS. 



VAI.I 



C. O. Nieolay, in th- ' Manual of Geographical Scirmv.' Put though 

 the aea-buins or ocean-hollows may be included witliin the necessary 

 geometrical definition <{ valley*, M Iwiflj? depressions below the 

 average level of the external surface of the solid cniat of the globe, 

 ad continent* and inlands within t li.it uf mountain*, a* being elevations 

 bore it, we conceive that some distinction in thin respect should be 

 established in the nomenclature of geology Mid physical geography. 

 The surface of the globe above which continents and inlands are railed, 

 that is, the bed of the sea, universally, cannot be considered as 

 identical, aa a geographical or geological element, with, the surfaces of 

 those masses of land themselves, on which are the minor, and in this 

 sense secondary, elevations and depressions we commonly call moun- 

 tains and valleys. Many of the phenomena of configuration and 

 physical state presented by the latter could only have been occasioned 

 by causes connected with the agency of an aerial atmosphere ; and 

 while many of them also have had a subaqueous origin, yet the con- 

 figuration of those parts of continents and islands which are below the 

 level of the sea must have been received from operations exclusively 

 subaqueous. The forms of the proper surface of the land were 

 produced originally by its elevation through the surface of the ocean to 

 a subae'rial position above it, and have been completed by atmospheric 

 and fluvial erosion. 



Many valleys, for example, were first excavated by marine currents 

 during their elevation, and. have been reduced to their present figure 

 by the rivers which have flowed through them from the period of the 

 elevation above the sea-level of the eminences which bound them. 



But the forms of the masses constituting continents and islands 

 have been produced by the agency of elevatory and marine forces only, 

 except in the cases of the subsidence of land previously fashioned 

 more or less by atmospheric action. However, the chief differences, 

 probably, between the configurations of the surface of the land and 

 those of the more extended surface consisting of the sea-bed and the 

 land regarded as one, depend on their relative magnitude and on the 

 depth of the sea, which, in fact, is merely the measure of the vertical 

 dimensions of the latter. Around the islands of that part of the Im'.o- 

 Australian archipelago which is physically a portion of Asia, the sea is 

 so shallow that those islands may truly be regarded as the summits of 

 mountain-masses separated by valleys of very inconsiderable depth, 

 inferior indeed to that of many of the terrestrial valleys upon them. 

 Those islands are in fact united by a vast submarine plain, which 

 abruptly terminates westward near the north-eastern coasts of Borneo, 

 in the middle of the Straits of Macassar, and in the Strait of Lombock, 

 in an unfathomable ocean. We then come to the inland-masses of 

 Lombock and the chain immediately to the west, the Moluccas, New 

 Guinea, and the other Australian islands, rising abruptly again from 

 the bottom of thus ocean, and thus exemplifying one of the peculiar 

 characters of the masses of land which rise from and bound ocean- 

 hollows ; and how characteristic of them is the form thus produced 

 will appear in the sequel. Islands fundamentally volcanic especially 

 if, like Teneriffe, they contain one principal volcano are probably 

 altogether conoidal, the submarine portion being merely the continuation 

 of the subacrial. [VoLCANOS.] 



Another difference, originating in the different process of formation, 

 is this : while mountains proper have characteristically smaller dimen- 

 sions above than below, and thus approximate more or less nearly to 

 the figure of triangular prisms, of pyramids, or cones, their altitude 

 being their principal dimension, the masses of continent* and islands 

 are tabular in form, with sides of every degree of obliquity, and some- 

 times very nearly vertical, their upper surface being much greater in 

 area than their sided, their altitude being their least dimension, and 

 their form thus approximating to that of a low parallelepiped. Valleys 

 proper, again, are widest at the top, and approach in general to the 

 form of an inverted triangular prism, more or less obtuse or acute, or 

 to that of an inverted pyramid, or to the frustum of such a prism or 

 pyramid, the edge or apex being replaced by a plane the floor of the 

 valley ; while the intervals between continents are almost as tabular in 

 form as the masses of the land, but their lower surface, while its area 

 is much greater than that of the sides, being less than the upper 

 formed by and at the level of the sea, [SOUNDINGS, DEEP SEA.] 



The configuration of land above the level of the sea which most 

 nearly resembles the continental masses is that which is called Talilt- 

 tamil, such as the table-lands of Tibet, Eastern Africa, and Mexico ; and 

 the intervals which separate different portions of them most nearly 

 answer to the ocean-hollows between continent*. As an example of 

 this may be cited the hollow between the table-land of Tibet on the 

 south, and its recurvature called the Thian Shan, being a portion of 

 North- Western China, on the north, of which the plain or plateau of 

 Yarkoihl and Khotan, anil what is termed the valley of Lake Lhop, 

 form the bane, and which, if we compare the two portions of the 

 table-land to mountains, will answer to a valley, according to the com- 

 mon mode of description. [ PLAINS.] Thin comparison will hold good, 

 and is illustrative in another respect Colonel Strachey, in his ' Physical 

 Geography of the Himalaya*' (not yet published, but quoted in ' Diil. 

 Trans.,' 1859, pp. 774-776), represent* that " the summit of the table- 

 land (of Tibet), though deeply corrugated with mountains and valleys 

 in ] tail, in in rU general relief laid out horizontally." Thin description 

 will accurately apply to the maw of elevated land which forms a conti- 

 nent or great inland, of which it may always be said that while ita 



summit is corrugated with valley* and mountains. It is in ita p. 

 horixontal. 



We are led by the previous comparison, and on further investigation, 

 to the apparent fact, that some portions of the earth's surface, however, 

 above the sea-level, present us with the essentially unaltered configura- 

 tion of other portions which are still below it From the united geo- 

 graphical researches and inductions of Dr. Thmuaa Thomson, Dr. 

 Joseph D. Hooker (' Himalayan Journals,' voL ii., p. 399), and Professor 

 James D. Forbes, it has appeared that the structure of Norway very 

 closely, resembles, on a small scale, that of Central Asia, particularly of 

 the Himalaya ; and that if it were so elevated that the bottom of the 

 deep fiords which penetrate it became dry land, we should have a 

 model of the Himalaya, with ita deep valleys and high acute summits ; 

 or, conversely, if the latter country were depressed, so that those 

 valleys became ocean-hollows, the land and mountain-peaks remaining 

 above the sea-level would correspond, on the great scale, to the moun- 

 tain-peaks of Norway, and the submerged valleys to the fiords. Dr. 

 Thomson (' Western Himalaya and Tibet,' p. 492) has extended this 

 comparison to the structure of Scotland, well known to resemble that 

 of Norway, and to be, in fact, a continuation of it He has also 

 described (pp. 429-438) the remarkable elevated plain of Karakoram, 

 south of the pass of that name, occupying an immense concavity in 

 the great chain of the Koucn-lun, the northern face of the tY> 

 of Tibet. It measures from six to eight miles in diameter, and has a 

 mean altitude of not less than 17,000 feet, being surrounded by great 

 depressions separating it from the mountains. It has the appearance 

 of having formerly been the bed of a lake, but is itself crossed by 

 several ranges of hills, and by a rivulet, and has a water-parting. This 

 is evidently the configuration of an island in the ocean, agreeing, 

 therefore, with the examples above described. 



Conversely, a portion of the bed of the Atlantic, from the coast of 

 Ireland westward, has a configuration resembling that of tin- Lurl \ 

 Western Europe ; but still further west, the great Atlantic depression, 

 very unlike a terrestrial valley, commences abruptly, the depth of the 

 sea increasing, within a distance of twenty miles only, from 1320 to 

 9000 feet, forming a sort of marine cliff on a gigantic scale. For at 

 least a thousand miles the whole surface is one vast depressed plateau, 

 which, according to Professor Ansted (in his 'Geological G<>,- 

 work deserving of a more appropriate title), is " totally unlike any 

 equal extent of dry land, though more resembling that on the eastern 

 side of the Andes, in South America, than any other known land." 

 On the (North) American side of the Atlantic plateau " there is a second 

 cliff, facing eastward, having a total rise of about 5000 feet, inimi- 

 diately to the west of which the ground slopes gradually upwards at 

 the rate of about forty feet in a mile, till it reaches the American 

 continent." 



We thus arrive at the final confluence of the two branches of the 

 subject. The elevations and depressions of certain parts of the globe, 

 of various magnitudes, closely resemble some of the continental masses 

 and ocean-hollows ; while the latter more generally have a distinct and 

 peculiar character ; and the corrugations of the upper surface of those 

 masses, ordinarily termed mountains and valleys, in their actual con- 

 dition, usually differ from both, aa already represented. In a paper 

 ' On the Lines of Deepest Water around the British Isles,' by the 

 Rev. 11. Everest, F.G.S., read before the Geological Society of London, 

 on June 19th, 1861, and which will probably appear in the ' Quarterly 

 Journal' of that Society, the student will find new materials fur pur- 

 suing this particular subject. 



Some geographical observers, because a river-basin (defined in the 

 article RIVERS) is necessarily bounded by high land, except \\1. 

 declines to the sea, employ the terms " basin " and " valley " of a river 

 indiscriminately and convertibly. Thus, Mr. Alfred R. Wallace begins 

 the chapter of his ' Travels on the Amazon and Rio Negro,' headed 

 " The Physical Geography and Geology of the Amazon Valley," with 

 the statement that " the basin of the Amazon surpasses in dimension 

 that of any other river." Now, although, strictly speaking, the differ- 

 ence between river-valleys and -basins is comparative only, and merges 

 in nature, yet this practice leads to erroneous conceptions of fact ; for 

 though a wide valley, through which a river of moderate dimensions 

 having many small tributaries takes its course, may be termed a basin 

 (sometimes called a valley-basin), yet the main stream, as well as ita 

 tributaries, must each have its own separate valley, however shallow : 

 such is the Thames, which is described as having a basin, while its 

 valley is often not recognised, though some of its affluents flow through 

 well-characterised valleys. [TIJAMI*, in (Ii:oc;. Div.] On the other 

 hand, the basin of a great river may, and in fact must, include many 

 such wide valleys; and a river-basin, more properly, is the country 

 which is made up of them, and the drainage of which at last finds its 

 way into one stream, and through one principal outlet into the ocean. 

 In this sense, the depression through which the upper course and 

 affluents of the river flow may sometimes be regarded as the basin, 

 while that giving passage to tin- \--\\<r course is properly termed it* 

 valley. In the case of the Nile, the depression through which HP- 

 single stream runs for 1300 miles, from the junction of its last 

 affluent, the Atbara, to the Mediterranean, that is, its lower course, is 

 projierly the valley of that river ; while its basin comprehends a vast 

 extent of country in Africa, to the eastward, southward, and south- 

 west of that point, made up of many valleys of large dimensions, some 



