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One of the most common features of the hills is the occurrence of a bed of igneous stones,-at one place large (30 to 60 cubic feet) slaggy and often scoreous or amygdaloidal, and gradually but irregularly diminishing in size until they become a coarse and then a fine gravel, in some places dwindling into a seam of minute grains. The beds are of various thickness,—from three or more feet to a few lines, and so, often, is the same bed at different places. They may consist of a uniform aggregate of stones, or of stones mingled with loose clay, sand, &c. Over this deposit there is generally a bed of soft clay, or sandy clay, Sometimes more than one bed of gravel occurs. Layers of unaltered angular fragments are occasionally, but rarely, found beneath these beds. Layers of the small porcellanous, jaspideous, and varnished stones before noticed, and of large grains of quartz, are more common. All these layers sometimes appear in the same section, but this seldom happens. The localities where the large scoriform rocks abound are often at or near the summits of hills, or where thick dykes of igneous rock come to the surface, and probably in every case they mark the places where the largest fissures or vents were opened. Where they are most abundant they appear at the surface, and that not only in spots exposed to denudating influences, but in fattish and gently sloping tracts. There appears in many cases to be a connection between the direction of the dykes and fissures, and that of the hills or their spurs. Where good sections of the summits of dykes have been obtained fragments of the rock of which they are composed, not angular but scoriform, can generally be traced as a horizontal layer on the surface, or disposed beneath a bed of clay, &c. to a considerable distance from the head of the dyke. When the dyke is vertical these stones are accumulated over and strewed on both sides of it. When it is inclined they are spread out in the direction towards which the inclination is. Two dykes adjoining each other at the surface have sometimes beds of scoriæ diverging from them in opposite directions, owing to their dips being opposed. The above and other observable facts are all, I think, explicable by the species of volcanic action which I have suggested, susceptible as it is, of various modifications, without resorting to oceanic agency. At all events no fact has yet come under my notice unequi
but lasted, or were from time to time repeated, for sometime after the elevation of the hills.
vocally attesting the abrading, sorting, or transporting operation of a large body of water, or which could not be referred to some known form of volcanic agency. It must also be borne in mind that the convulsive mechanical action which enters so largely into the general hypothesis, would be most powerful in shattering compact and loosening soft rocks, when the stratified masses were ruptured and raised into highly inclined, vertical or reversed positions. In such cases the exposed basset edges, in their fragmentary or pulverized state, and before they were protected by any vegetation, would be more acted on by meteoric causes than at present.
The system of hills with their dykes and veins affords an interesting field for the application of the principles of mechanical science. But it would be premature to enter on this subject before the country is better opened up, as it will soon be by the lines of road now in progress. There can be little doubt however that the directions of the hills agree with the ramifications of fissures which in those places where the intensity of the elevatory force caused their extension to the surface, have formed vents through which the superficial volcanic deposits were expelled. The principal ranges, we have seen, are nearly parallel and have directions approximating to N. W. and S. E. The lateral hills are placed on lines at right angles to these, and the secondary lateral hills again on lines parallel to the principal ranges.
My remarks have been hitherto confined to facts entirely local, and inferences or hypothesis strictly deduced from, or applicable to them. Before concluding this paper, however, let us extend the limits of our observations, and see whether a wider geological area presents phenomena repugnant to the large influence which has been assigned to volcanic causes.
That the movements which elevated the central mountains of the Malayan Peninsula had an intimate relation with those that elevated the mountains of Sumatra, seems evident, whether we regard the hypothesis of De Beaumont, the more recent observations and theories of Mr. Darwin, or the mechanical researches of Mr. Hopkins. Both form long chains which pursue parallel lines not more than 3 or 4 degrees distant. But we must probably take in a much wider geographical range if we would seek a general geological theory for the region which they traverse. The mountain chains of the Peninsula of India
are parallel, or approximately so, to the Malayan, and like them, spring from the great central system of Asia. The chain of the Peninsula of Malaya is directly continued to this region, and from it descend nearly parallel chains through Burmah, Siam and Cochin China. These ranges determine the general direction of the sea coasts wherever these are exposed to waves sufficiently strong to prevent the formation and extension of alluvial plains. The western coasts of India and of the Tenasserim Provinces, Siam, the gulf of Siam and the eastern coast of Cochin China are thus fixed. A wide and interesting field of inquiry is opened up by the probable geological connection between the regions of these ranges and those of the Indian Archipelago generally, Australia and the Archipelagoes of the Pacific, evidenced by the prevalence of parellel lines of elevation, and perhaps also by organic remains, such as the fossil elephant and some of the carboniferous plants of New South Wales. The former existence of a great Australasian continent, an extension probably of the present continent of Asia, which seems to result from Mr. Darwin's theory of Atolls, would be an inference in accordance with these facts. Viewing the whole region, interspersed with peninsulas and islands, from the Indian Ocean to the heart of the Pacific, as one, it appears that De Beaumont's theory of parallel rectilinear or oblong areas of elevation and subsidence, which Mr. Darwin has applied to the eastern tracts, requires modification, and that if we conceive curvilinear lines or systems of parallel curvilinear lines proceding from centres and often meeting similar lines or systems from other centres, and again lateral and secondary lines diverging from the principal, the arrangement of the observed ranges will assume greater symmetry, and be found perhaps to accord with the hypothesis that one widely extended mechanical pulsion, accompanied by local foci of intense development from weakness in the rocks or increased plutonic or volcanic action, gave the first direction to all the main lines ot' elevation. Thus let us conceive such a centre to be situated in the western half of New Guinea, and we have some independent warrant for doing so, in the circumstance that the mountains of its unexplored interior appear to attain a magnitude unusual in the Archipelago. From this focus we may trace one great curvilinear fracture or band of rupture of the earth's crust through the Sunda Islands to Chittagong ; a second through the mountainous volcanic islands of Ceram and Bouro, and
along the southern coasts of Celebes and Borneo (Gaonong Ratos), Billiton, Banda, the Malay Peninsula, &c.; a third through the Phillipines, Formosa, Japan, &c.; a fourth along the southern coast of New Guinea, and through the Solomon Islands, New IIebrides, New Zealand, &c. ; a fifth along the southern coast of New Guinea, across Torres Straits and along the eastern coast of Australia, and a sixth perhaps through the north-western division of Australia. Other principal lines probably proceed across the Moluccas and Celebes, through Borneo and the isiands of the China sea (now a subsiding tract), and join the mountain chains of Cochin China and Siam, but the geography of Borneo is not sufficiently known to allow of our positively ranking these as seventh and eighth lines. The intermediate areas may be ocempied by numerous other lines, but the subsidence of various tracts renders it difticult or impossible, particularly to the castward, to trace the ori ginal courses of vertical movement until the soundings of the Polynesian seas are ascertained. Subsequent shifting subterranean action would cause many other fractures in various directions, but it would not, at least until the lapse of a long geological epoch, obliterate the primary lines. It would often cause cross fractures, of which many instances might be pointed out. It is no objection to this hypothesis that many of the lines seem to proceed from the central table-land of Asia. Because if at the time these fissures were being extended southward, a great local action took place at or near New Guinea, they would, according to the mechanical laws examined by Mr. Hopkins, diverge from their original direction towards that point, or to meet the lines radiating from it. Thus we observe the two least broken lines to pursue a southerly direction till they reach the parallel of 8° N L., when, at the Nicobars in the one and at Junk-ceylon in the other, they are deflected to the S. E. When they cross the meridian of 106° E. they make a more decided bend to the eastward. If we follow these lines and the chains of Siam and Cochin China northward we may trace them upwards to the Bayan Khara mountains, and thence to the vast central mass of Kulkun, from whence great ranges are said to proceed towards all the points of the compass. But in the north-western part of the province of Yunnan and north-east of Burmah and Assain their continuity is interrupted, and we seem to have ascertained another central region whence radiate not only the lines which afterwards converge to New Guinea,
but various other curvilinear ranges proceeding S. E., E., N. E., and N. through China, and N. and N. W. through Thibet, and lastly, the Himalayas and a minor range proceeding south-eastward on the south of the valley of Assam, and continued perhaps in the Vindyas, -for a subsequent line of subsidence passing down the plain of the Ganges and through the Bay of Bengal, of which there is some evidence, may have destroyed the pre-existing continuity. Many of these ranges proceed primarily from the Kulkun, but it is remarkable that they converge towards the region indicated. The region where the Himalayas attain their sublimest proportions and give birth to rivers that embrace them and all India in their courses, is another grand focus. From this centre the range proceeds on the one side to the eastward, and on the other to the N. W. To the north of the former a secondary and approximately parallel range also proceeds eastward, and includes with it the valley of the Sanpao, and to the south another and smaller secondary parallel range traverses upper India. To determine the original centres of maximum intensity and directions of the forces that elevated the great connected mountain system that forms the skeleton of the Asiatic continent, is a problem beyond the present reach of geology.*
The Malayan chain I have mentioned as a series of groups, and from the breadth of country which their members occupy compared with their height and apparent bulk, and their general appearance as viewed from the Straits, I am led to believe that they consist of connected systems, each analogous to that of the Singapore hills, or of principal undulating masses from which parallel ranges proceed in a N. W. and S. E. direction. The rivers probably have their sources at the heads of the valleys included between these ranges and turn seaward at the
* There can be little doubt that an extensive knowledge of the physical and mineralogical constitution of mountuin ranges will form the true basis of the highest department of the science, now only dawning, -the Mechanism of the Earth. But the day is probably not far distant when the geologist, like the astronomer, will need to be thoroughly indoctrinated with the principles of mechanical science in its widest sense. Fortunately for the worshippers of nature of humbler acquirements, geology is so immersed in matter, so wrought into every inch of the earth, that its Priests have need of a whole tribe of Levites. Wherever a man finds himself placed he has but to employ his eyes to become a useful labourer, and so far will a little knowledge be from proving dangerous to him that it may be safely said, that while even entire ignorance is not a bar to the collection of facts, every little accession of knowledge from any of the sciences becomes an instrument of observation.