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450 feet deep. Near by, W. A. Fernando has opened a mine 330 feet deep, but at a higher level. The other important mines are situate in the district of Kaltura. According to further communications from A. M. Fergusson the graphite veins strike from south to north in the Western Province and from east to west in the Kurungala district.
From F. Sandberger's work I extract the following physiographical and chemical facts :—The graphite is coarsely foliated or " stalky," and includes kernels of quartz, orthoclase, radiating hornblende, mica, apatite, pyrites, weathered andesine and chloritiferous kaolin. Especially interesting is the occurrence of many colourless rutile crystals and of acicular pseudomorphs of titanic iron which permeate the mass of the graphite.
During last spring, after a visit to the gem pits of Ratnapura (at the southern base of Adam's Peak) I sailed for two days with Professor F. Exner of Vienna in a boat on the Kaluganga to Kaltura, and had an opportunity during this trip of examining a graphite mine, and the geological appearance of the mineral may deserve some little interest.
About halfway between Ratnapura and Kaltura a bar of hard granite closes ihe bottom of the valley, and the river forms a violent and dangerous rapid. On the left bank lay great heaps of graphite blocks which had been brought out of the jungle by coolies and which were being shipped from below the rapid. The graphite was very soft, partly in minute scales, partly " stalky," and blocks of a cubic foot in size, of the finest graphite, occurred in the heaps. Individual blocks consisted of stalk-like parallel masses, 20 centimetres in length, but others showed a very confused structure. Nothing special could be gathered from the coolies about the mode of occurrence, and the pits were too distant to be looked up. The next day, when we were still about six hours' sail from Kaltura, we saw in the scrub jungle, on the eastern bank, a section about 300 paces from the river, and left the boat in order to examine it more closely.
The grey "domoid" gneiss which predominates in that part of Ceylon and which rises everywhere out of the virgin forest in mighty domes of blocks, was here so greatly weathered to a depth of 12 metres that it could be cut with a knife. The product of weathering was a pale red mass of kaolin with many small red spots and individual harder laminae crumbling into quartz grit. I do not hesitate to term this decomposition rock laterite, as all the transitions exist from the genuine deep red laterite to this pale red-spotted rock which comes to pass in situ out of the bedded grey gneiss.
From this light red laterite exposed in the quarry to a depth of 12 metres, a system of much-branched veins of black graphite stands out most conspicuously. Cingalese workmen were occupied in breaking out the graphite with iron picks, and others carried the mineral away to the rock-cut steps.
The main vein strikes nearly E.-W., hades 6o° north, and varies in thickness from 12 to 22 centimetres. Many apophyses branch off from the main vein, and other smaller veins, which either split up speedily into small branches, or else unite quickly with neighbouring veins, run parallel with the main vein. In their form the veins differ in no respect from the quartz veins which are so frequently to be seen in the gneiss of Ceylon. I broke out a piece of the main vein with the "Sal-bands" on both sides, and packed it as carefully as I could, but it arrived in Jena in the condition of minute fragments.
The graphite is stalky and the stalks stand perpendicular to the "Sal-bands." By subsequent movements along the cleft the "stalks" have been bent in many places. The " Sal-bands" distinguish themselves most by their red colour.
In the laterite outside of the veins I nowhere found graphite in nests or spangles, and the " Sal-bands" also appeared quite free from included specks.
As to the mode of formation of this graphite, four views appear to be possible:— i.—As graphite has frequently been observed as a quasi-sedimentary inclusion in normal connection with stratified rocks, this assumption should also be tested here and examined to see if an originally horizontally bedded band of graphite might not now be presenting the appearance of a vein-system because broken up and faulted by subsequent dislocations. A careful examination of the locality showed that such a view was untenable, and that the observer is confronted by a genuine system of fissure veins.
The pointed ends of the graphite apophyses have no corresponding extensions, and as far as one can judge from the sandy and clayey bands of the laterite of the original bedding of the gneiss the graphite veins cut such at considerable angles. The only assumption which thus remains possible is that fissures originated in the unweathered gneiss by dislocations, which fissures were filled up with graphite. When at a later period the gneiss decomposed into laterite the carbon-filled veins remained unaltered and are so found in the laterite to-day, a speaking proof that this rock was formed in silu and has not been " remanie."
(2) .—Although it has just been shown that the graphite here is a true veinstone
there yet remains the second and more difficcult question to answer. How did the graphite veins originate, and how could the carbon fill up the fissures in the gneiss? The view that the carbon was forced up in an irruptive condition is repudiated by F. Sandberger on the strength of his observations. Although the geological occurrence of Sandberger's graphite is unknown, it is yet probable that it came from a vein in the decomposed or the unaltered gneiss. The author says: "It can be positively asserted that the igneous method is quite excluded, as the graphite contains iron pyrites which can never originate in the presence of a high temperature, while the acicular rutile crystals would have been reduced to metallic titanium by the great excess of carbon.
(3) .—If the graphite could not get into the fissures as a compact (but once
molten) substance, it is yet conceivable that a carbonaceous combination dissolved in water might have saturated the rocks and have been reduced to graphite in the fissures. Such a view appears to me untenable for two reasons. Firstly, we are unacquainted with any such process and any such carboniferous solution; and assuming even that such a solution could be established, I do not quite understand why the adjacent rock does not also contain graphite. If the graphite was reduced from an aqueous solution, the entire rock or at least the "Salbands" should be impregnated with minute spangles of graphite. I examined the laterite on the spot carefully in view of this, but could not discover any trace of graphite in it ,the Salbands also were perfectly free from graphite, i.e. they were light red in colour without any greyish admixture. Thus, the probability of the carbon having got into the fissures in the igneous way becomes exceedingly small.
(4).—As far as I am able to judge the relations, only one possibility remains, to which there is no serious objection, and which I discussed fully with my fellow traveller on the spot. Although the formation of the graphite as an intruded material, or out of an aqueous solution, meets with serious objections; it yet remains conceivable that it may have got into the fissures in gaseous form. It is not probable that the carbon itself was sublimed ; but among the hydrocarbons, rich in carbon, we meet with combinations which are easily sublimed, and, what appears to me yet more important, really play a great part in nature, and perfectly saturate mighty rock formations. Hydro-carbon exhalations are known all the world over, and spectroscopic analysis teaches us that they play an important part in cosmic bodies which are not so far advanced in their development as is the earth. Secondly, we know then in the flues of gas-works and cooking furnaces a substance is deposited which has many properties in common with graphite. It would appear from many experiments that it is from cyanogen compounds that the gas-furnace graphite is precipitated, but for us the fact is important that it is a product of sublimation. All is strongly in favour of the view that the Ceylon graphite has been reduced from carboniferous vapours, but of what kind such vapours were is another question.
The minerals included in the graphite must then be regarded partly as fragments of the original gneiss, and partly as subsequent segregations from solution.
Whether all graphite has originated in this way is a question that might be difficult of discussion as long as our knowledge of the tectonic occurrence of the graphite remains so imperfect. It appeared to me fairly probable that the graphite which occurs in the gneiss of the Amsteg tunnel on planes of a slickenside was of similar origin.
Anyhow I think I should point out that the view (apparently a very sensible one) that graphite represents the remains of the archaic flora, is not quite tenable.
It is very tempting to place graphite at the end of a progressive alteration series beginning with peat and brown coal and leading up through coal to anthracite.
From the mineralogical side, objections have been made to the inclusion of graphite in this series, and the observations made on the mode of occurrence of the Ceylon graphite are calculated only to increase those objections.
One may hold no decisive views as to the aqueous or gaseous filling of the graphite veins; but at any rate its occurrence in veins will not fall in with the view which regards the graphite as altered cellulose.
Extracts from the Journal of a trip to the Glaciers of the Kabru, Pandim, &c, by PRAMATHA NATH BOSE, B.SC, F.G.S., Deputy Superintendent, Geological Survey of India.
The following extracts from the journal of a trip to the snowy regions of the Himalaya, undertaken in September 1889, are published partly because they contain geological notes, which, however scanty and disconnected, may be of some value, relating, as they do, to a country but little explored, and partly in the hope that they may be of some service to future travellers. Sikkim is being fast opened up. Last year the Nepal Frontier Road was extended one stage beyond Phalut, that is to say, a stage nearer the snows. And, in a few years, tourists will, I have no doubt, be discussing trips to Aulakthang or Giuchala, asithey now do to Sandokphu or Phalut.
There are to my knowledge four published accounts which cover portions of our journey. The earliest and best known of these is the "Himalayan Journals," by Sir Joseph Hooker. His journey in the direction we went, being undertaken in the depth of winter, could not be pushed beyond Jongri, two stages south of the glaciers we reached. He went via Yoksum, the route4.we took on our return journey. The next account is that of Captain W. S. Sherwill.1 The point he reached was a long way south of Jongri; in fact only one stage beyond Migu, our third march from Phalut. The only parties that preceded us, as far as I am aware, to the Giuchala pass, are those of Major J. L. Sherwill,8 and of the Alpine traveller Mr. W. Graham."
The geological observations interspersed through the Journal, meagre as they are, taken in connection with those on the eastern frontier of Sikkim made by Dr. Blanford4 in 1870, and by me in October last year on a trip to the Pemberingo pass near Gnathong, enable us to form an idea, though a very rough one, of the geological structure of Sikkim. The central portion consists of glossy mica schists1 quartzites, carbonaceous slates, &c, belonging to the Daling series of Mallett.* These are surrounded on all sides by gneissose rocks of a distinctly more ancient aspect. A portion of the southern boundary between the Dalings and the Gneiss, which lies in the district of Darjeeling, has been shown by Mr. Mallet to be faulted.6 On the west side, I crossed the junction at two places, near Lingcham (south-west of Pemionchi) and near Chakang. At both these places, the Dalings and the Gneiss agree in their dips, so that the former pass under the latter. Whether the underlie is real, or only apparent, being the result of a reversed fault, I am unable to say exactly. No trace of the Gondwanas was met with anywhere. My time on the glaciers was too short to admit of detailed exploration. But something, however little, has, I venture to think, been added to our existing information about them.
I am indebted to my fellow-traveller, Mr. J. C. White, Political Agent, Sikkim, for many acts of personal kindness.
']. A. S. B., Vol. XXII, 1854, pp. 540-611.
3 J. A. S. B., for 1862, p. 457.
8 Proc, Royal Geog. Soc, Lond., Vol. VI, 18S4, p. 429, tt seq.
4 ]. A. S. B., for 1871, p. 367.
1 Mem., Geol. Surv. of India, Vol. XI, p. 39.