TRAVANCORE STATE MANUAL Volume One
V. NAGAM AIYA
Dewan Peishcar, Travancore kingdom
1. Physical Description - Section B — Geology
Travancore owes its shape to the erosion of the old crystalline rocks which has taken place on a most gigantic scale. Dr. King points out the quasi-terraced arrangement the country shows, descending by steps, as it were, from the mountains to the coast. This terrace arrangement is much less well-marked in South Travancore than further to the north-west. The several ten-ace steps are marked by the existence of some ridges near the coast higher than the general surface of the country further inland. The most conspicuous of these is a considerable mountain pass lying north and north-east of the old Fort of Udayagiri.
In the northern part of the country, the mountain mass is very broad, but just south of Peermade, the hilly backbone narrows considerably and becomes a lengthened series of more or less parallel ridges with lower and lower intermediate valleys. The real southern termination of the Ghatits occurs in latitude 8015’N., where the high mountains sink down into the Aramboly Pass. Southward of the pass rises the perfectly detached Kattadimala, a fine rocky mass 2,000 to 3,000 feet high, which sends off a rocky spur extending southwards with two breaks, for a distance of 7 or 8 miles and terminating in the bold Marutwa hill, 4 miles north-west of Cape Comorin. The cape itself consists of low gneiss rocks, backed up by a palm-grown sandhill, about 100 feet high. A pair of very small rocky islands rise out of the sea a few hundred yards east of the Cape, and various other rocks occur off the coast opposite Muttam, Colachel and Melmadalatora which are the culminating points of reefs formed by ridges of gneiss running parallel with the coast. These rocks, especially one called the Crocodile Rock, were sources of great danger to the coasting ships but the danger has now been removed by the erection of a lighthouse on the Muttam headland. At Colachel, the seaport of South Tmvanoore, the lie of the rocks is such that it would be easy to connect them by short rubble breakwaters and thus to form a very useful little harbour in which coasting craft could easily lie up during the south-west monsoon,
A broken band of younger rocks occupies a very great part of the tract lying between the coast and the Trivandrum-Tinnevelly high road. There can be no doubt that these rocks, not very long since geologically speaking formed an unbroken belt which extended considerably further inland than at present. The denudation they have undergone has been very great, both vertically and laterally, and the remnants left of them are in various places of such trifling thickness that all traces of their former existence will soon be effaced. They show most in the western fart. of South. Travancore where they form small plateaus, which are well marked except to the north, on which side they lap on to the rising surface o£ the gneiss and thin out or are lost sight of in the Kabuk or pseudo laterite formation — a rock resulting from the decomposition of ferruginous beds of gneiss. The surface of the plateaus, where not greatly eroded, is gently undulating and often supports a very dense and varied vegetation. The less compact portions of plateau surfaces are often cut into small, but very deep, rain gullies which render many places impassable for any but foot passengers.
The various geological formations to be found in Travancore may, for convenience of reference, be arranged in a tabular scheme as below:
The Gneissic Series-
“The gneisses are generally of the massive grey section of the series, that is, they are nearest to the rocks of the Nilgiris, though they differ from them in being coarse-grained or more largely crystallized, and in being generally quartzose rocks. So quartzose are they, that there are, locally, frequent thin beds of nearly pure quartz rock which are at times very like reefs of vein-quartz. Often these beds are strongly felspathic, the felspar occurring among the quartz in distinguishable grains or larger crystalline masses, giving the rock rather a granitic appearance. The only other region where I know of somewhat similar beds of quartz rock occurring with other gneisses is in the schistose region of the Nellore District. There, however, the quartz rock becomes often a line compact quartzite; here in Travancore, there are no approaches to such compact forms.
NOTEs: Note: A regular and systematic Geological Survey of Travancore has yet to be undertaken. But in connection with the operations of the Geological Survey of India, Dr. W.King and Mr. R.Bruce Foote have closely examined the country and their observations have been largely utilised in the writing of this section.
‘The common gneisses are felspathic quartozse varieties of white or grey colours, very largely charged with garnets. A particular form of them is an exceedingly tough, hut largely crystallized, dark-grey or greenish felspathic rock. Massive horn-blendic gneisses are not common. Indeed horn-blende maybe said to be a comparatively rare constituent of the Travancore gneisses.
“All the gneisses are more or less charged with titaniferous iron in minute grains; they are likewise — only more visibly — as a rule, highly garnetiferous. In fact, one might say that Travancore is essentially a country of gametiferous gneisses. The garnets themselves are only locally obtainable, it being impossible to break them from the living rock while they are generally decomposed or weathered. They are generally of small size, but are very rich in colour, the precious garnet being very common. Other minerals such as red, blue and yellow sapphire and jacinth, arc found among the garnet sands so common on the seashore at certain places. The sea-sands are also full of titaniferous iron grain. I may instance the beautiful and long known constitution of the shore sands at Cape Comorin where, on the beach, may be seen the strongest coloured streaks or ribbons, of good width, of bright, scarlet, black, purple, yellow and white sands of all these minerals and the ordinary silica.
“The general lie of the gneisses is in two or three parallel folds striking west-north-west to east-south-east. There is, perhaps, rather a tendency of the strike more to the northward in the broad part of the hills about Peermad, and on towards the Cochin territory. Thus between Trivandrum and Tinnevelly on the west coast or for some twelve to twenty miles inland, the dip is high to the South-south-west inland of the terraced or plateau country, or among the first parallel ridges there is a north-north-east dip; then, on the mountain zone, there is again a high dip generally to the south-south-west.
“Thus the inclination of the beds is generally high, right across the strike with a crushed-up condition of the folds; but they are often at a low angle, and the anticlinal on the western, the synclinal on the eastern, side are plainly distinguishable. About Kurtallam (Courtallum), on the Tinnevelly side, the rise up from the synclinal is very well displayed, and in their strike west-north-westward into a broad mountain land, the beds of this place clearly take part in a further great anticlinal which is displayed in a great flat arch of the Peermad strata. With this widening out of the mountain mass there is rather an easier lie of the strata. Southwards from the Ariankow traverse there is much crushing up of the beds; but they roll out flatter again towards the southern extremity, and there are good indications of a further synclinal to the south-south-west in the northerly low-dipping beds of Cape Comorin.
“Foliation is very strongly developed indeed it is here, practically, bedding and lamination, of which there are some wonderful exhibitions. At Cape Comorin, indeed, some of the gneiss in its weathered condition (not lateritized) is scarcely to be distinguished, at first, from good thick-bedded and laminated sandstones and flaggy sandstones.
“There is no special development of igneous rocks either in the way of granites or greenstones, though small veins and dykes are common, generally running nearly with the strike of the gneiss. In South Travancore, or north of the parallel of Trivandrum, there are stronger occurrences of granite in which mica is abundant and in largish masses.
“The great feature about the gneisses in Travancore and indeed also in Cochin and Malabar, is their extraordinary tendency to weather or decompose, generally into white, yellow, or reddish felspathic clayey rocks, which, in many places and often very extensively, ultimately become what is here always called laterite.................. Very soon after one begins to leave the higher ribs the mountains and to enter on the first long slopes leading down to the low country, the gneiss begins to be weathered for some depth into a clayey rock, generally of pale colours, streaked and veined with ferruginous matter, and having always an appreciable upper surface of scabrous or pisolitic brown iron clay, which is, of course, probably largely the result of ferruginous wash, and less so, of ferruginous infiltration. Also the ferruginous s and lateritoid character is devolved to a certain extent according to the composition of the gneisses; but, on the whole, there is no doubt that the upper surface generally over large areas is lateritized to a certain depth irrespective of the varying constitution of the strata. Then as the rocks are followed or crossed westward the alteration becomes more frequent, decided, and deeper-seated; though still, all over the field, ridges, humps, and bosses of the living rock rise up from the surrounding more or less decomposed low-lying rock areas.
“This generally irregular and fitfully altered condition of the gneisses begins at an elevation of about four hundred feet above the sea, and thus it extends as a sort of fringe of varying width along the low slopes of the mountains. At a yet lower level, say from two hundred to one hundred and fifty feet, and so nearer the sea coast, there is a better defined belt of more decidedly lateritized form of weathered gneiss, in which the unaltered rock occurs less frequently, and then always in more or less flatly rounded humps and masses, which never rise above a general dead level. This belt is, in fact, a country of undulating downs or tolerably uniform level stretches of forest land. Occasionally, it also shows a plateau surface or it is broken into small and low flat-topped hills. Always it is very deeply indented by river or stream valleys, or even by some of the backwaters which have high and steep shores.
“It is remarkable of this coastal belt of country that its laterite (an altered or ferruginously infiltrated condition of weathered or decomposed gneiss) is not to be distinguished from any other laterite, except that which is made up of obviously detrital material. Whatever the laterite of Travancore or Malabar may have been originally, it is a useless form of the rock, being crumbly and soft as a general rule, and oftener of a red colour than brown. The character of the climate does, in fact, appear to militate against the changing of the red peroxide of iron in the rock to the brown peroxide, during which change the proper cementing and hardening of the sound rock, such as that on the east coast or in the Deccan is evidently brought about.”*
NOTEs: *General Sketch of the Geology of Travancore, W.King B.A, D.Sc -- Records of the Geological Survey of India, Vol XV
Regarding South Travancore, Mr. Bruce Foote writes:
“In no part of the peninsula, is there a greater and finer display of the ancient crystalline rocks than in the southern Ghauts in their southern half, and in the great spurs and outlying masses on their western or southern side. The disposition of the beds in South Travancore shows the existence of a great synclinal curve, probably an ellipse, the major axis of which passes through or very near to the great mass of Mahendragiri; while the north-western focus (if the ellipse be a complete one will be found somewhere to the north-eastward of Allepy. I had inferred the existence of this great synclinal ellipse from studying the course of the great gneiss beds on the eastern foot and flanks of the mountains southward of Courtallum, and Mr. King’s examination of the gneiss country across the Shencotta pass and southward to Travancore independently demonstrated the existence of the central part of this huge synclinal fold.
“The topographical shape of the ground points strongly to the fold being a true ellipse, the extreme North-western extremity of which is probably hidden under the alluvial bed north of Allepy, while the extreme south-eastern apex lies most likely in the sea to the E. N. E. of Cape Comorin. The curve of the coast from Cape Comorin north-westward to close up to Trivandrum coincides with the south side of the great synclinal, and the different ridges inland also coincide absolutely with the strike of the harder beds of the series. Several southerly dips were noted in the rocks on the coast westward of Kolachel which looks as if the axis of an anticlinal had there been exposed, but they may possibly only represent trifling vandyke-shaped bends or crumples, in the side of the great synclinal. To the north of the area under consideration the rocks roll over northward into a great anticlinal fold.
‘’The true bedding of the gneiss on a large scale is extremely well displayed in the great outlying mass known as the Udagiri or ‘Muroovattoor’ mountain. Both strike and dip are admirably seen from the Travellers’ bungalow at Nagarkoil. One of the finest examples of a sheer naked wall of rock to be seen in Southern India is shown in the tremendous cliff forming the south-east front of the Thiruvana Malai, the great eastern spur of Mahendragiri. This bare precipice must be fully 2,000 feet or more in height, many hundred feet in the central part being absolutely vertical, or even overhanging a little. As might be expected, this great mass has attracted much notice; it forms the Cape Comorin of some sailors, and of Daniel’s famous view of that Cape, though in reality some 16 miles from the nearest point on the coast and 28 miles from the Cape itself. Even the Hindu mind has connected this noble mountain with the name of Hanuman, the famous monkey God, who is said to have planted one foot on each of the two peaks and to have jumped across the Gulf of Mannar and alighted on Adam’s Peak, a standing jump of 220 miles and odd being a trifle for the long-tailed divinity. Another grand precipice occurs on the south-east face of the Taduga Malai at the western end of the Arambuli Pass. The cliff-faces in both these splendid scarps coincide with the great planes of jointing.
“The predominant character of the gneiss rocks in this quarter is that of well-bedded, massive, (quartzo-felspathic granite gneiss), with a very variable quantity of (generally black) mica and very numerous small red or pinkish garnets. This is the characteristic rock at Cape Comorin and very generally throughout South Travancore, and Tinnevelly District as well.
“Scattered grains of magnetic iron are commonly met with in the weathered rocks. No beds of magnetic iron were noted by mo, but some may very likely occur, and would go far to account for the numerous quantity of black magnetite sand cast up on the beach at frequent intervals along the coast and of which the source is at present unknown, unless it has been brought by the south-westerly current prevailing during the south-west monsoon. The source of the garnets which form the crimson sand which is of nearly equally common occurrence, is not far to seek, for it is hardly possible to find a led of rock which does not abound in garnets. The so called ‘fossil-rice’ found at the extreme point of land close to the Cape is merely a local variation of the quartz grains set free by degradation of the rock. They assume the ‘rice’ shape after undergoing partial trituration in the heavy surf which beats incessantly on the southern coast.
“The sub-aerial decomposition of the felspatho-ferruginous varieties of the gneiss produces in the presence of much iron a pseudo-laterite rock very largely developed over the gneissic area described by Dr. King in his Sketch of the Geology of Travancore under the name of lateritised gneiss, a rock which is popularly called laterite in Travancore and Kabuk in Ceylon. In numberless places this peculiar decomposition of the gneiss, which is preeminently characteristic of very moist climates, has altered the rook in situ to variable but often considerable depths, and the original quartz laminae of the gneiss remain in their pristine position, and often to all appearance unaltered, enclosed in a ferruginous argillacious mass formed by the alteration of the original felspar, mica, garnets and magnetic iron. The colour of this generally soft mass varies exceedingly from pale whitish pink to purple, red and many shades of reddish brown and brown, according to the percentage of iron and the degree of oxidation the iron has undergone. The bright colours are seen in the freshly exposed Kabuk or pseudo-laterite, but the mass becomes darker and mostly much harder as the haematite is converted into limonite by hydration, and more ferruginous matter is deposited, as very frequently happens, by infiltration. The pseudo-laterite formed by accumulation of decomposing argillo-ferruginous materials derived from distant points is to be distinguished generally by the absence of the quartz laminae as such. The quartz grains are generally much smaller, and are scattered generally through the whole mass of new-formed rock. One excellent example of the pseudo-laterite formed by the decomposition in situ is to be seen in a steep bank in the Zoological gardens in Trivandrum, close to the Tapir’s den. Equally good examples are very common in many of the cuttings along the high road east of Trivandrum.
“The washed-down form of pseudo-laterite often forms a rock intermediate in character between a true sub-aerial deposit and a true sedimentary one, and consequently by no means easy to classify properly. In fact, in a country subject to such a tremendous rainfall, the sub-aerial rocks must, here and there, graduate into sedimentary ones through a form which may be called ‘Pluvio-detrital.’ Such pluvio-detrital forms occur very largely in South Travancore, but it is impossible in most cases to separate them from the true sedimentary formations they are in contact with.”*
NOTEs: * Records of the Geological Survey of India, Vol XVI
The Varkala Cuddalore Sandstone Series
To quote Dr. King again —
“The next succeeding rock formations, namely, the Quilon and Warkilli beds, occur as a very small patch on the coast between the Quilon and Anjengo backwaters. The Quilon beds are only known through the researches of the late General Cullen who found them cropping out at the base of the low laterite clifts edging the backwater of that place, and again in wells which he had dug or deepened for the purpose. I was myself not able to find a trace of them#. They are said to be argillaceous limestones, or a kind of dolomite in which a marine fauna of univalve shells having a eocene facies was found; and they occur at about forty feet below the laterite of Quilon, which is really the upper part of the next group.
NOTEs: # Mr. Logan says that these have since been satisfactorily identified as occuring at a place called Parappakkara on the Quilon backwater about 6½ miles north-east of the Residency.
“The Warkilli beds, on the other hand, are clearly seen in the cliffs edging the seashore some twelve miles south of Quilon, where they attain a thickness of about one hundred and eighty feet, and have the following succession in descending order —
Laterite (with sandstone masses.
Sandy clays (lithomarge.
Sandy clays (with sandstone bands .
Lignite beds with logs of wood &c..
“The bottom lignite beds rest on loose white sand, and nothing is known of any lower strata.
“It will be seen how this set of strata has an upper portion, or capping of laterite, which is however clearly detrital. On the landward edge of the field of those Waikilli beds, there is in places only a thin skin, representative of these upper beds, of lateritic grits and sandstones lying directly on the gneiss, which is itself also lateritized; and it is very hard as may be supposed, to distinguish the boundary between the two unless the detrital character of the former deposits is well displayed. Thus the upper part of the formation has overlapped the gneiss. It is also this upper portion which overlies the Quilon beds, which arc also apparently overlapped.
“These Warkilli beds constitute, for so much of the coast, the seaward edge of the plateau or ten-aced country above described, and they present similar features. The Warkilli downs are a feature of the country—bare, grass-grown, long, fiat undulations of laterite, with, about Warkilli itself, small plateau hills forming the higher ground — one hundred and eighty to two hundred feet above the sea. These downs, too, and the small plateaus or fiat-topped hills, are partly of the Warkilli laterite and partly of the lateritoid gneiss.
“Whatever form of denudation may have produced the now much- worn terrace of the gneissic portion of the country, the same also had determined the general surface of the Warkilli beds. Indeed, it gradually dawned on me while surveying this country, having the remembrance of what I had seen of the plateaus and terraced low lands in Malabar in previous years, that here, clearly, on this western side of India is an old marine terrace which must be of later date than the Warkilli beds. These are, as I have endeavoured to show in another paper,* of probably upper tertiary age and equivalent of the Cuddalore sandstones of the Coromandel. Hence this terrace must be late tertiary or post-pliocene, and it marks, like the long stretches of laterite and sandstones on the eastern side of the country, the last great or decided elevation of Southern India, prior to which, as is very probable, the Indian land rose almost directly from the sea by its Western Ghauts and had an eastern shore line which is now indicated very well by the inner edge of the Tanjore, South Arcot, Madras, Nellore and Godaveri belts of laterite and sandstone.
NOTEs: * The Warkilli beds and reported associated deposits at Quilon - Records of the Geological Survey of India, Vol. XV
“Mr. Foote has already generalised in this way for the eastern side of Southern India in particular but I think he makes the elevation too great, including, as he does in his laterite deposits, patches of the laterite gravels and rock masses ranging up to a height of live hundred feet at least which are not so definitely part and parcel of the proper coastal developments.”
The following account of the Cuddalore Sandstone series, marine beds, blown sands, coral reefs and soils is extracted from the very exhaustive paper on The Geology of South Travancore by Mr. Bruce Foote from which we have already quoted —
“A very careful examination of the beds near Quilon by Dr. King who had the advantage of seeing the fresh cuttings made through plateaus of these rocks in connection with the new tunnel at Warkilli has unfortunately thrown no positive light on their true geological position. The vegetable remains associated with lignite beds at base of the series proved insufficient to allow of determination of their own character and consequently most unsuitable to assist in settling the homotaxy of the strata they occurred in. The sedimentary beds forming the belt of small plateau fringing the coast of South Travancore must, on petrological grounds, be unhesitatingly regarded as extensions of the Quilon beds, or Warkilli beds of Dr. King.
“None of these formations which I traced from Villinjam, nine miles south-east of Trivandrum, down to Cape Comorin afforded the faintest trace of an organic body thus no light was thrown on the question of the geological age or homotaxy, but somewhat similar sandstones and grits are found on the Tinnevelly side of the extreme south end of the Ghauts range, and in a coarse gritty sandstone, much resembling some of the beds in Travancore, a bed of clay is intercalated, in which occur numerous specimens of Arca-rugosa and Cytherea of a living species. The locality where these fossils of recent species were found occurs on the right bank of the Nambi-ar, about two miles above its mouth and a few hundred yards from the bank of the main stream. All the sub-fossil shells I found here are of living species hence the deposits enclosing them cannot be regarded as tertiary; and if the agreement of these Nambi-ar beds with the Warkilli and South Travancore beds, on the one hand, and the Cuddalore, Madras, and Kajamundry beds be assumed, as they must be on petrological grounds, the Cuddalore sandstones and their equivalents elsewhere must be accepted as of post-tertiary age. As far as it goes the evidence is clear and distinct; but more evidence is required as to the age of some of the intermediate connecting beds, such as those south and east of Kudankulam.
“The typical section of the Warkili Rocks near Quilon, given by Dr. King shows the following series —
with which we may compare the series seen in the fine section formed by the beautiful clifts in Karruchel bay, 11 miles south-east of Trivandrum.
“The section here exposed shows the following series of formations: —
4. Soil—dark red, sandy loam, lateritic at base—8 to 10 feet.
3. Sandstone—hard, gritty, purplish or blackish—?
2. Sandstone—gritty, rather soft, false-bedded, often clayey in parts (lithomargic), variegated ; in colour red, reddish Brown purplish whiteyellow—40 to 50 feet.
1. Sandstone—gritty, rather soft, false-bedded, red, purple, pink, white, variegated ; shows many white clay galls producing conglomeratic appearance in section—40 feet.
Base not seen, hidden by sandy beach.
“The total thickness of these beds I estimated at about 100 feet; the upper part is obscure, from pluvial action washing down the red soil over the dark grits. The middle and lower parts of the section are extremely distinct, and: the colouring of the beds very vivid and beautiful; but the bed are by no:means, sharply defined.
“The beds dip north-easterly (inland, and from the slope of the ground on the top of the cliff the angle of dip may be inferred to be from 20° to 30°. Further inland, near Pinnacolum, the dark gritty sandstones lie horizontally, at a considerably lower level than at the top of the Karruchel cliffs, but rise again to the eastward. The middle gritty series is exposed along the western* aide ot the Karruchel lagoon, but is highly, lateritised by weather action. Three miles to the north of the lagoon, purplish gritty beds show strongly and form a small well-marked plateau overlooking the valley in which lies the village of Cottukal. That the gritty beds are sometimes replaced by clays is shown by the materials turned out of two deep wells sunk into the plateau at two points several miles apart; one of these wells lies rather more than half a mile to the northward of Mullur. Here the section, which is from 80 to 100 feet deep passes through mottled gritty sandstone and into blue and white mottled clay. The other section revealing clays below the gritty beds is a well sunk close to the new road from Valrampur to Puvar.
“A section in the low cliff forming the small bay immediately east of Villinjam shows a mottled vermiculated clayey rock showing mostly no bedding at all. Traces of bedding are, however, revealed as the cliff is followed south-ward by the appearance of thin bands of grit near the base of the section which rests on the underlined quartzo-felspathic garnetiferous gneiss. This mottled clayey, rock I believe to represent the bluish white mottled clay turned out of the lower parts of the well section near Mullur before referred to. It is locally considerably discoloured and stained by the percolation of water through the overlying pseudo-lateritic dark-red sand. As will be seen by any one who follows the coast line these Warkilli sandstones rest upon a very rugged and broken gneiss surface. Many great tors and knolls of granite gneiss protrude through the sandstone plateau or tower over them from adjacent higher ridges, which have been completely denuded of the younger rocks.
“The greater part of the surface of the tract occupied by these Warkilli beds west of the Neyar is thickly covered by sandy loam, generally of dark red colour, which conceals the sub-rock very effectually, excepting where the loam is deeply eroded. A well marked patch of purplish grit forms a knoll, about a mile southwest of Valrampur. Traces of the former more easterly extension of these beds are to be seen at intervals along and to the north of the Trivandrum-Tinnevelly road between Valrampur and Neyatankarai.
“In the tract lying east of the Neyar few sections exhibiting the grits &c., were met with, and all were small and unsatisfactory’. The surface of the country is either largely covered with the deep red soil or else the extremely broken surface of the gritty beds is extensively lateritised. The appearance of the country, when seen from elevated points is, however, characteristically very different from the gneiss and Kabuk tract lying to the northward. This may be well seen from Colatoor Trigonometrical station hill, as also from the high ground close to Cauracode, but yet more striking from the Kodalam Pothai, a hill 2 miles west-north-west of Paurashalay. Sections in which the fine character of the rock is to be seen occur on the high ground close to the junction of the new roads leading from Puvar and Martanda Putentorai respectively to Paurashalay, also to the southward near Shoolaul, where a large rain gully cuts deeply into the grits and underlying clayey beds; also along the ridge of high ground north and north-east of Yeldasaput. Traces of the former eastward extension of the grits were noted on the eastern flank of the Kodalam Pothai and on high ground half a mile or so to the northward of the Cutcherry at Paurashalay. The beds composing this patch of Warkilli rocks have undergone greater superficial denudation than those in the Karruchel patch to the north-west.
“In the small patch lying east of the Kulitorai river some instructive sections of hard rock grits and underlying clayey grits of the usual, reddish, bluish, and white mottled colour are to be seen south of Killiur. Some of the sections show regular miniature ‘canons’ 15' to 20' deep, with vertical sides and numerous well-formed pot-holes. Hard purplish grits show on the surface between Killiur and Pudukaddi and soft mottled grits in a well section close east of the D. P. W. bangalow at Tengapatnam. At the southernmost point of Killiur patch, the grits become coarsely conglomeratic over a small area. A little to the north of this the grits, when resting on the basset edge of a bed of granular quartz rock, present the characters of a perfect arkose, made up of the angular gneiss debris. In places this arkose might be most easily mistaken for a granitic rock.
“A distinctly conglomeratic character is shown by the grit beds close to Madalam. This Madalam patch of Warkilli sandstones is on its southern side deeply cut into by a gully which exposes regular cliffs with from 35 to 40 feet of coarse or conglomeratic mottled grits, capped by thick red soil. The grits contain many large clay galls and lumps of blue or mottled colour.
“In the Kolachel patch the grits are extremely well exposed in deep cuttings (miniature canons) made by the stream rising just west of Neyur. They are of the usual mottled description. Where seen at the eastern side of the patch near the Eranil Cutcherry they are quite conglomeratic. They are exposed also in a gully crossing the road which runs north from Kolachel to join the main road, and in a well section on the high ground a mile north-eastward of the little town. The south-eastern part of the patch is entirely obscured by a great thickness of dark red soil. They peep out, however, below the red soil at the western end of the great tank 3 miles south of Eranil.
“A very thin bed of conglomeratic grit underlies the teri, or red sand-hill, capping the high ground north of the Muttum headland. Further east a few poor sections only of whitish or mottled grit prove the extension of the Warkilli beds in that direction, nor are they well seen again till close into Kotar, where they show in various wells and tanks, but are still better seen in a deep rain gully south of the Travellers’ bangalow at Nagarkoil and in a broad cutting immediately to the east of the bangalow. The variegated gritty sandstones here seen are very characteristic, and strongly resemble some of the typical varieties in South Arcot and Madras districts.
“To the south of Kotar the grits are to be seen in stream beds opening to the Purrakay tank, and in a series of deep rain gullies on the eastern slope of a large red soil plateau to the south-west of Purrakay.
“A small patch of gritty sandstones of similiar character to the above occurs immediately north and north-west of Cape Comorin. As a rule, they are badly exposed, being much masked by the red blown sand of a small teri. The most accessible section is a small one seen in the bottom of a good sized bowrie, a little south of the junction of the roads coming from Trivandrum and Palamcotta. This section can only be seen when the water in the bowrie is low. A considerable spread of similar greyish or slightly mottled grits is exposed about half a mile to the north-east of Covacolum and 1½ miles north-west of the Cape. Lying between the two exposures just mentioned, but separated from either by spreads of blown sand, is a different looking vermiculated mottled grit of much softer character. This is extensively exposed in the banks of a nullah and head water gullies falling into the Agusteshwar. The colour of this soft grit ranges from red, through buff to whitish. The beds roll to the northward. This grit is full of vermicular cavities filled with white or reddish Kankar (impure carbonate of lime). The grit seems to graduate upward into a thick red gritty soil full of small whitish red, impure (gritty calcareous concretions. There is good reason, however, for thinking that this graduation is merely apparent, and that the red gritty soil is only the base of a red sand-hill, or teri, undergoing change by percolation of calciferous water. A hard brown grit is exposed for a few square yards just north of the junction of the two roads above referred to. This rook has, except in colours, considerable resemblance to the red-white grit just described, and both probably overlie the pale mottled grits near Covacolum.
“The last patch of grits to be mentioned forms almost the extreme easterly angle of the Travancore territory and lies to the eastward of the southernmost group of hills and along its base. Not many sections of the grit are here exposed owing to a thick red soil formation which laps round the base of the hills, and is only cut through here and there by a deep rain gully or a well. The grits here seen are like those exposed near the Travellers’ bangalow at Nagarkoil; but show much more bedding and are almost shaly in parts. The colour of the grit is white, pale drab or grey mottled with red and brown in various shades.
They lie in depressions in the gneiss, and were either always of much less importance and thickness than the beds to the west, or else have been denuded to a far greater extent. They are best seen in gullies to the south-west and west of Russhun Kristnapur, 7 miles north of Cape Comorin, and in the beds of the small nullahs west and north-west of Comaravarum opposite the mouth of the Arambuli pass. None of these Warkilli grit beds occurring between Trivandrum and Cape Comorin have yielded any organic remains as far as my research has gone, and I fear none will be obtained by subsequent explorers. The alum shales occurring in Dr. King’s Warkilli section have not been traced in South Travancore, and I had not the good fortune to come across any lignite. It is said to occur not unfrequently to the south of Kolachel, and to be turned up by the people when ploughing their fields. I have no reason to doubt this, for it is extremely probable that some of the clayey beds should contain lignite. From the configuration of the ground, too, the paddy flat along the southern boundary of the Kolachel grit patch would coincide in position with some of the clayey beds near the base of the series which are lignitiferous at Warkilli; and why not at Kolachel?
“The recent discovery of lignite in the Cuddalore sandstones at Pondicherry adds greatly to the probability of the correctness of Dr. King’s and my conclusion (arrived at by us separately and independently before we had an opportunity of comparing notes that this gritty bed in Tinnevelly and Travancore should be regarded on the grounds of petrological resemblance and identity of geographical position as equivalents of the Cuddalore sandstones of the Coromandel Coast.
“At Cape Comorin and two other places along the coast to the northward are formations of small extent but very considerable interest, which, by their mineral constitution and by the abundance of fossil marine shells they enclose, show themselves to be of marine origin, and thus prove that the coast line of the Peninsula has undergone some little upheaval since they were deposited. These beds are to be seen close to the Cape at the base of a small cliff which occurs immediately south of the Residency bangalow and only about two hundred yards west of the Cape itself. The rocks seen in the surf and immediately behind it on the beach are all gneiss. The base of the small cliff is composed of friable gritty calcareous sandstone, full of comminuted shells. The base was not exposed at the time I examined the section, some heavy gale having piled up the beach sand against the foot of the cliff, and for this reason it was impossible to trace the probable connection of the sandstone with another exposed at a slightly lower level at a few yards distance to the west. This lower bed is similar in mineral character, but very hard and tough, and offers great resistance to the surf but has nevertheless been deeply honeycombed and in places quite undermined.
“The roofs of the miniature caves thus formed have in some cases fallen in, but have been partly re-cemented by deposition of the calcareous matter in the lines of fracture. To return to the cliff section, the basement sandstone is overlaid by a similar but slightly harder yellowish friable bed, which contains many unbroken shells (all of living species), in addition to a great quantity of comminuted ones. The base of the lower bed is hidden by sands, but from the proximity of the gneiss it cannot exceed 5 or 6 feet in thickness, while the overlying shelly bed measures about the same. It is overlaid in its turn by a massive bed, 6 to 10 feet thick locally, of a kind of travertine formed of altered blown sand, composed mainly of fully comminuted shells. This travertine contains immense numbers of shells and casts of Helix vittatta the commonest land shell in the south. Owing to the soft character of the marine sandstones, the cliff has been much undermined by the tremendous surf which breaks on this coast in bad weather, and great masses of the hard travertine of the Helix bad have fallen on to the beach, forming a partial breakwater against the inroads of the sea.
“The shells contained in the upper sandstone bed were all found to be of living species, where sufficiently well preserved for specific identification; the majority of the specimens are too ill preserved for specific identification. Four miles north-north-east from the Cape, stands the little stone-built fort of Wattakotai, which is built upon a small patch of calcareous sandstone, full of marine shells, exposed in the most along the north face of the long curtain wall which joins Wattakotai fort with the extensive series of fortifications known as ‘Travancore lines’. The marine limestone may be traced for nearly half a mile inland in the bottom of the moat. This marine bed is overlaid by a very thin bed ot travertine limestone full of Helix vittata; it has been cut through in the formation of the moat. The thickness of the shelly marine bed is unknown, but the Helix bed is not seen to exceed 10” or 1” in thickness. As far as seen in the very small exposure, both formations lie nearly horizontally. Another small exposure of the marine bed occurs at the western end of a little backwater to the north of the fort. The sandstone here contains many well-preserved marine shells, all of living species; but further west, where the bed is exposed below the Helix bed in the moat, the enclosed shells are all broken and comminuted. The surface of sandstone, as seen at the end of the little backwater, is raised but a very little distance above the sea-level, probably not more than 4 or 5 feet at the outside. The rise of the ground along the moat is extremely small, and even at the furthest point from the sea at which the sandstones are exposed the elevation is probably not more than 10 or 12 feet at most, which would correspond with the top of the sandstones as seen in the little cliff at Cape Comorin.
“About two miles north-east-by-north of Wattakotai fort a small patch of white shelly limestone occurs peeping out of the low bait of blown sand which fringes the coast at that spot. The village of Kannakapur which lies immediately to the north is the last within the Travancore boundary. The limestone only stands out a few inches above the surface of the surrounding sands, and no section could be found to show its thickness, but in point of elevation above the sea-level it agrees perfectly with the Waitakotai and Cape Comorin beds. The limestone which is fairly hard is quarried for economic purposes, and unless a good deal more of the bed than now meets the eye remains hidden under the sands, it will, before many years are over, have been removed by human agency.
“The shell remains occur as impressions and casts of great beauty and perfectness, but the shelly matter has disappeared entirely, being probably slightly more soluble than the enclosing limestone. The limestone contains a large number of specimens of Helix Vittetta which were evidently carried out to sea and there entombed in a shallow water formation. To any one who has noticed the enormous numbers of this Helix living in this neighbourhood, and in the southern districts generally, the large numbers of it occurring fossil in this marine bed will be a matter of no surprise.
“Two very marked varieties of Aeolian rocks occur along or near the coast of South Travancore, as well as along that of Tinnevelly. They are the red sands, forming the well-known teris of Tinnevelly, where they are developed on a far larger scale, and the white sands forming the coast dunes. In South Travancore, as far as my observation went, the red sand hills are no longer forming; all are undergoing the process of degradation by atmospheric agencies at various rates of speed. The red sands have in many places ceased to yield to the influence of the winds and have arrived at a condition of fixity and compaction caused by the action of rain falling upon the loose sands percolating through them and during heavy showers flowing over their surfaces and washing the lighter clayey and smaller, though heavier, ferruginous particles down the slopes of the hills or into hollows on the surface, where, on drying, a fairly hard, often slightly glazed, surface of dark red loam has been formed. This loam is very fairly fertile and soon becomes covered with vegetation, which further tends to bind the mass together and render the surface secure from wind action.
“The loose sand, deprived of the clayey and finer ferruginous particles, would, unless unusually coarse in grain, be carried off by high winds elsewhere or remain in barren patches on the surface. I believe this process has gone on extensively over many parts of South Travancore, and explains the existence, on the surface of the country and resting indiscriminately on the gneiss and the younger rocks as the Warkilli sandstone, of the great thick sheets of pure red loam which have not been brought there by ordinary aqueous deposition nor formed in situ by the decomposition of the underlying rocks. The percolation of the rain water through the mass has in many places given rise to the formation of concretionary ferruginous masses, which are often strongly lateritoid in their aspect. The quantity of clayey matter and of iron ore in the form of magnetic iron is very great in the sand of many of the teris. The greater quantity of the water falling on the teris, as on their blown sand surfaces, escapes by percolation, and it is a common phenomenon to find springs issuing around the foot of the sand mass during the rainy season and becoming dry in the hot or rainless season.
“The teris in South Travancore which still retain their character as accumulations of moving red sands are four in number and all very small, the largest not measuring one sq. mile in area. They are all close to the coast and with one exception stand high and conspicuous to ships passing along at a fair distance. The largest and most conspicuous is that at Muttum which caps the high ground with a new lighthouse. The process of fixation has gone on here largely and the moving sands cover a much smaller space than does the fixed portion. The same may be said of the teri resting on the south-eastern extremity of the Kolachel sandstone plateau. To the north-west of Koluchel are two much smaller teris at the distance of 3 and 5½ miles respectively. In both of these also the area of the fixed sand far exceeds that of the loose. Especially is this the case in the more northerly teri near Melmadalathorai. Here the fixed part has undergone tremendous erosion and is traversed by long and deep rain gullies, with vertical sides up to 20 or 25 feet high. Gullies on a yet larger scale are to be seen at the south-east corner of the Kolachel sandstone patch and at the eastern side of the Muttum patch. Very large but shallower gullies are to be seen at the south-east corner of the Nagarkoil patch, where there is a very large fixed teri.
“The small teri immediately behind the Cape Comorin is a very poor specimen of its kind, and, in fact, hardly deserves to rank as one owing to its pale colour and poverty in iron sand, but it will not do to class it as a coast dune, as it consists mainly of silicious sand, while the true dune at the Cape consists mainly of calcareous sand composed of comminuted shells, corallines, nullipores &c.
“The sand of the typical teris is silicious or ferruginous (magnetic iron, the former being well rounded and coated with a film of red-oxide of iron, which is removable by boiling in Nitric acid for a few seconds. Common as garnet sand is on the beaches of South Travancore, I never yet found a grain of it in the teri sand, where the latter was pure and had not been mixed with beach sand.
“The coast dunes of South Travancore are, except close to the Cape, in no way remarkable. A large pat;h of small hillocks to the north-west of the mouth of the Kulitorai river was caused by the wind shifting a great mass of sand turned out when the new canal was dag and heaped up on the north bank of the canal.
“Some tolerably high ridges occur three miles south-west of Kolachel. The sand here contains so much fine magnetic iron that it looks in parts of a dark grey colour, shading here and there almost into absolute black.
“A considerable quantity of blown sand fringes the coast from the Muttum headland eastward to Cape Comorin, and between Pullum and Culladevella forms some considerable hills. At Covacolum the highly calcareous beach sand which forms many low hillocks has been solidified in several places into coarse shelly limestone. The Helix bed at Cape Comorin already referred to, when treating of the Marine beds, is really an altered sand dune, the calcareous matter of which has, by percolation of acidulated water, been dissolved and re-deposited, on evaporation of the water, as a sub-aerial travertine. Countless thousands of Helix vittata and a considerable number of shells of Nanina tranqucbarica, the two commonest land shells in this part of India, have been enclosed and fossilised in the formation of this travertine, which is evidently in constant progress. The immense wealth of shell fish of all kinds, added to large quantities of corallines and nullipores, incessantly thrown up by the surf, furnishes an abundant supply of calcareous sand for the formation of this travertine, which forms a bank more than a mile long and rising some 80 feet or more above the sea at its highest point. Its inland extent cannot be ascertained, as it is covered by loose sands. It probably only extends 300 to 400 yards inland and abuts against a low ridge of gneiss”.
“A few tiny fringing reefs are to be seen half to three-fourths of a mile west of the Cape, half in the surf at low tide, and wholly in it at high tide. They are now to be considered as dead reefs, abandoned by the polypes that built them. I examined most of them carefully, without finding any live coral, and was inclined to doubt the correctness of my inference, drawn from their tabular shape and many shallow basin-like cavities; but later on, when examining some identical fringing reefs off the Tinnevelly coast to the south of Kudankulam Trigonometrical station (the south point of the Cape Comorin baseline), I found a considerable quantity of live coral lining the sides of the little basins and equally large quantities of coral quite recently dead in adjoining basins.
“A great deal of shell debris, sand and broken stone, is included in the mass of the reefs which in several places have formed around masses of rock standing in rather shallow water, and joined up many loose blocks of stone tossed on to them by the surf into tremendously coarse conglomerates. Some similar reefs but of rather larger size, occur along the coast to the north-east of Cape Comorin; in these the tabular mass extends from 10 to 40 and 50 feet in width, from the shore to the constantly surf-beaten outer edge. In one or two places parts of the reef had evidently been founded on sand, which had been washed away, leaving an unsupported surface of many square yards in extent which the surf of the next high tide or first gale of wind would either break up or else again support with sand washed under it. These little reefs are worthy of much closer examination than I was able to bestow upon them.
“The coral fauna of the Cape Comorin sea is on the whole a remarkably poor one, as far as one may judge by what is to be found thrown up on the beach. Dredging might reveal much more, but unfortunately no boats are found there, only Kattumarams (Catamarans) which would not be the most convenient form of craft from which to carry on scientific observations. The sea here is, however, so very rich in animal life in many forms, that it could assuredly afford a rich reward to any one having a suitable vessel at command. I obtained in a very short time, a far larger number of species of shells here than at any other place on the Indian Coast.
“The prevalent soils (of South Travancore) are red ones varying in the quantity of their ferruginous element. The red soils seen inland near the main trunk road are chiefly formed of gneissic debris by sub-aerial decomposition. The origin of the deep red sandy or clayey loams has already been discussed. They occupy no inconsiderable area. True alluvial soils occur very rarely, if at all, now-a-days; those which fill the bottoms of the many valleys and creeks in which paddy is cultivated being greatly altered from their original condition by centuries of cultivation, and the addition of various mineral, vegetable and animal manures. Estuarine beds full of sub-fossil shells, Cytherca, Pottamides, Melania &c., of living species are exposed in the salt pans at the mouth of the Kolachel nullah.
“The Alluvium in the valley of the Paleyar, which flows south from the west flank of Mahendragiri past Nagarkoil is, where pure, a coarse gritty silt.”
There are two anchorages on the Malabar Coast, known to mariners from early times. The bottom of these anchorages consists of a very fine, soft, unctuous mud which has over and over been supposed to act as a barrier against the force of the waves of the sea. Ships can not only ride safely in these roads, but they can also sometimes take in fresh water alongside, the sea beneath them being so diluted with fresh water from inland sources. At times the smooth surface on one of the banks may be broken by huge bubble “cones” as they have been called, of water or mud from the sea-bed, and even roots and trunks are reported to have floated up with these ebullitions.
Again the banks of mud are not fixed in position but move along the coast within ranges of some miles in extent; or one of them remains comparatively stationary while the other moves, and these movements do not take place year by year with the monsoons but continue over many years. Similar, though insignificant, patches of smooth water banks are found in various points along the Malabar Coast. But the best-marked and most generally known are those near Cochin and Alleppey. That near Cochin or the Narakal bank may be said to lie between Cochin and the Cranganore river 11¾ miles to the north. For many years its position has been about the middle of the range. The Alleppey bank ranges from a mile or two north of Alleppey to Poracad, a distance of 12 to 15 miles. It is now at the southern end of this range and indeed is often called the Poracad mud-bank. The mud-banks lie close along the beach but extend some miles seaward presenting a more or less semicircular or flat crescentic edge to the long rollers and tumbling waves of the monsoon weather.
Ordinarily the sea is tolerably smooth only rolling on the shore with more or less of a surf, and these patches are only to be distinguished by the soundings of mud below them. It is only a few days after the bursting of the monsoon, when the whole line is affected and the mud in these particular places stirred up, that the patches are distinguishable. Then the muddy waters calm down and remain so for the rest of the monsoon.
The mud itself is essentially characteristic and unique. It is of a decided dark green colour slightly tinged with brown, very fine in texture, very soft and oily feeling, altogether just like a very fine soft ointment or pomatum. After a time it dries and hardens, loses its oily feel and becomes harsh like ordinary mud. Its oily consistency has been proved beyond doubt; the specimens analysed have been found to give off, when subject to distillation, some brownish yellow oily matter lighter than water and looking not unlike petroleum. The muds also contain a considerable quantity of foraminiferal and infusorial remains. Capt. Drury thus wrote on the origin of these banks —
“The origin of this deposition of so large a quantity of mud in the open sea about two or three miles from the shore and so many miles from any bar or outlet from the backwater has never been satisfactorily accounted for. From the circumstance of there being no natural outlet for the vast accumulation of waters which are poured down from the various mountain streams into the basin of the backwater nearer than thirty-six miles on either side, it is not improbable that there exists a subterraneous channel communication with the sea from the backwater through which the large quantity of mud is carried off and thrown up again by the sea in the form of a bank”.
Mr. Crawford, for a long time Commercial Agent at Alleppey, was of opinion that the perfect smoothness of the water in the roads and at the Alleppey beach was attributable not so much to the softness of the mud at the bottom as to ‘the existence of a subterranean passage or stream or a succession of them which, communicating with some of the rivers inland and the backwater, became more active after heavy rains particularly at the commencement of the monsoon than in the dry season, in carrying off the accumulating water and with it vast quantities of soft mud”. He found that at the periods of deficient rain the mud-banks were less effective as anchorages. He also observed that after or during heavy rains the beach suddenly subsided, slightly at first but gradually as much as five feet, when a cone of mud suddenly appeared above the water, bursting and throwing up immense quantities of soft soapy mud and blue mud of considerable consistence in the form of boulders with fresh water, debris of vegetable matter decayed and in some cases fresh and green.
Mr. Rhodes, the successor of Mr. Crawford, confirms the above observation and states that he has seen mud volcanoes bursting up in the sea during the rainy season, which appeared “as if a barrel of oil had suddenly been started below the surface”. He thinks that the mud thus formed is gradually floated away to the southward by the littoral current and fresh banks are formed whenever the hydraulic pressure of the inland backwater increases sufficiently to overcome the subterranean resistance of the stratum of fluid mud which is formed at certain places; and as a further proof, he adduces the fact that the extent of the mud-bank at Alleppey increases and diminishes as the level of the inland water rises and falls, as was most observable in 1882*.
NOTEs: * In regard to the formation of the bank, Mr. Philip Lake of the Geological Survey in his Note on the Mud-banks says: - "The chief point then in which I differ from pervious observers is in considering that the Alleppey bank is formed not from the backwater mud but from an older river deposit found only at particular points along the coast. This would explain its non-appearance at other points where the conditions seem equally favourable. With regard to the existence of subterranean channels, it may well be doubted whether any could exist in such unstable deposits as are found here"
The range of the coast exhibiting the phenomena is about 92 miles long tolerably straight, without any indentation giving the form of a bay except at the extreme ends, viz., at Quilon and Cranganore. There is no indication of a bay near Alleppey, the name ‘bay’ having perhaps been adopted from an imaginary bay of smooth water enclosed within the semicircle of breakers outside. The shore line is straight, low lying or only a few feet above sea level and made up of alluvial deposits and sand. Between Alleppey backwater and the sea there is no visible communication, the principal rivers that enter it flowing northwards behind the range of the mud-bank. To all appearance the flat lands of the coast are entirely recent alluvial deposits consisting of layers of sand and mud overgrown with vegetation. The humps of blue cliffs described by Mr. Crawford as turned up in the cones of Alleppey, answer to the lumps of clay of the lower part of the Varkala cliffs already described. Mr. Crawford also mentions his having passed through a crust of chocolate-coloured sandstone or a conglomerate mixture of the sandstone and lignite corresponding to certain rocks at Varkala.
It is clear that both the Alleppey and Narakal banks have practically the same constitution, behave similarly and have the same accompaniments with the exception of the violent discharges of mud or oil which are confined to the Alleppey bank.
It has already been remarked that the mud of these banks is full of organic matter and that it contains a sensible amount of oil probably partly derived from the decomposition of organisms. The mud is easily stirred up on all seasons and never settles down into a uniformly compact deposit but the upper stratum is in a greater state of liquidity than its lower depths. It occupies particular areas and within these well defined limits its movement is from north to south.
Regarding the water over the mud, Dr. King says#: —.
“It is only known to calm down during the S. W. Monsoon. The calming of the anchorages does not take place until after the monsoon has commenced and there has been a stirring up of the sea and mud. The quieting of the waters is intensified according to the amount of rainfall during the monsoon but even if no rainfall, there is a certain amount of quiescence. The calmness continues throughout the monsoon, apparently without any fresh stirring up of the mud. In one locality at least, the water is subject at times to violent agitation through the bursting up of gigantic bubbles of water, mud or gas, — it is not quite clear which; and these features also appear to be intensified during heavy rainy weather in the monsoon periods. The water over the banks becomes considerably freshened even to the extent — as I was told by Mr. Crawford — of being drinkable also according as the monsoon rains are light or heavy. At such times, also, the water gives off fetid odours, and the fish inhabiting it are killed off in large numbers; but whether owing to the freshening of the sea-water, or the exhibition of poisonous matter and vapour in the water, is not clear perhaps this destruction of life may be due to both causes.
NOTEs: # Considerations on the smooth-water anchorages, or mud-banks of Narakal and Alleppey on the Travancore Coast - Records of the Geological Survey of India, Vol XVII
The soothing of the troubled waters of the sea must surely be due to the oily constitution of the mud. An experiment performed sometime ago in the harbour of Peterhead, when a stream of oil was cast upon the heavy seas at the harbour’s mouth with such success that vessels were enabled to run in with comparative ease clearly proves this. Thus the action of oil on troubled waters is confirmed not only by tradition and anecdote but by actual fact; but the long continuance of the quiescence without any fresh stirring up is not easily accounted for. The amount of oil derived from the decomposition of the animal and vegetable matter of the organisms in the mud would be hardly sufficient to account for the features exhibited; hence we must look to other sources for the oil and even for the continued supply of mud itself which is evidently carried away and distributed by littoral currents.
The consensus of opinion certainly leads to the conclusion that there is an underground discharge of water at any rate into the sea from the lagoon and river system behind the Alleppey-Poracad Coast during flood-time, the inland waters being at a higher level than the sea. This passage of underground waters must, more particularly during heavy rains, force cut large quantities of the mud on which the Alleppey Poracad land rests like a floating bog, as it were, elastic and capable of yielding to pressure or exerting pressure by its own weight, while a continuous stream of the same oil and mud may be kept up under the lower pressure of the ordinary backwater level. In the monsoon time the heavy floods, which however occur only at long intervals, cause great discharges of mud, oil and gases and at such times new banks might be formed, the old ones being distributed down the coast by littoral currents arid finally dissipated into the open sea.
The presence of petroleum has to be accounted for by the fact that besides the alluvial deposits large lumps of clay or compact mud, more or less decayed, and vegetable remains are brought to the surface during the prevalence of the violent ebullitions. Such clays are met with in the Varkala deposits associated with lignite beds, in which occur trunks and roots of trees in every stage of decay. It is probable that the Varkala deposits may extend north under the Alleppey Poracad alluvium and even again at Narakal, where also fragments of similar clays are thrown up by the sea; and that it is in these deposits as being deeper-seated, older and lignitiferous that the earth-oil is generated.
Thus according to Dr. King, the mud banks, their smoothening influence, and their position within certain ranges of the coast, may be entirely due to the following causes —
“1. The discharge of mud from under the lands of Alleppy, Poracand and Narrakal, being effected by the percolation or underground passage of lagoon water into the sea.
2. The presence in this mud of oily matter, derived perhaps in part from the decomposition of organisms, but principally from the distillation of oil in subjacent lignitiferous deposits belonging presumably to the Warkilli strata.
3. The action of littoral currents which, slowly and through long periods of years, carry the mud down the coast to certain points whence it is dissipated seawards, — by the Quilon river at Narrakal, and at Poracaud because it is there beyond the range of replacement. “
According to Mr. Bruce Foote, valuable minerals and metals are conspicuous by their absence in South Travancore and this remark may be truly applied to the whole of Travancore.
The development of the gold industry in Southern India having raised hopes of gold likely to be found among the quartz out-crops of Peermade and the adjacent country, Dr. King was requested to examine those parts and report on the same. His report is conclusive. He says: —
“These out-crops are not reefs as usually understood but are true beds of quartz rock lying between and running w4tli other beds of the country rock which is of the crystalline or gneiss series, Reefs or veins of quartz generally run across the country rock as in Wainad or in the Kolar region of Mysore. Secondly the size of these out-crops is small, only one of them being sufficiently large to allow any expectation of what might be called a good tonnage of stone. Thirdly, and most important of all, the quartz of the out-crops, though it shows on a close assay traces of gold, is certainly not rich enough to be called auriferous quartz in the usual acceptance of the term.”
He found on examination that the ordinary crop of the Peermade Hills consists of a thin bed of quartz rock, largely made up also of felspar. He says that in all of the main outcrops of Peermade,
“the rock is more or less of the same constitution, that is, a quartz rock with very often a good deal of felspar distributed through it in small crystalline masses sometimes as large as peas, generally coarsely crystallised dull white and glassy quartz and less often a more compact rock like that of vein or reef. It is generally of a white colour, but at times it is stained red or even a golden yellow from ferruginous matter and scattered through it, there is often a small quantity of iron pyrites or frequent small particles of magnetic iron ore.
General Cullen was the first to discover graphite in 1843. In 1865 Dr. Royle discovered some specimens which were lamellar and soft but brilliant. Some samples were forwarded from a place south of Trivandrum for examination but were considered too soft and scaly for the manufacture of pencils. The matrix appeared to be a pseudo-laterite formed of decomposed gneiss in situ. Deposits were also found near Vellanad, the veins in which plumbago occurs being said to cross the strike of the gneiss. The plumbago found here is much purer than others. Mining work is carried on in three mines viz, Vellanad and Cullen mines in Ooozhamalakal Proverty, Nedumangad Taluq, and the Venganur mine in the Kottukal Proverty, Neyyattinkara Taluq.
The total output of plumbago during the last four years was as follows —
Messrs. Parry and Co. and The Morgan Crucible Company who work these mines pay a nominal Royalty to the Government of 4 or 6 Rs. per ton according to the quality of the plumbago mined.
Iron — Iron ore is found throughout Travancore in large quantities but as imported iron is much cheaper than the locally manufactured iron, the industry is given up. In the Shencottah Taluk iron is obtained as black sand in the brooks in Pulangudiyiruppu and Achanputhur villages. It is said that two persons working daily can take up 7½ Kottas or 126 Parahs of the sand in a month, and that 4 Parahs of this sand smelted with 40 Parahs of charcoal and ashes yeild about 80 pounds of iron. The selling price of this iron is 4 Rs. while the cost of manufacture comes to about 5 Rs. Hence the industry has been given up. It is also found at Pralakat in Cheranallur Proverty, Kunnattur Taluk, where an unlimited quantity of the ore is obtainable. Here the out-turn is said to be 10 lbs. for every 100 pounds of the ore. Iron ore is reported to be found at Aramboly in large quantities at a depth of 15 or 10 feet. This place was once noted for its iron smelting industry. As large quantities of foreign iron began to be imported the industry had to be given up here also.
At Myladi till about thirty years ago the people earned their livelihood by gathering iron ore at the foot of the Poranathumala after heavy showers when the ore is washed down from the top of the hill. This they used to remove in baskets to the nearest rock and holding up the baskets at sufficient height, allow the contents to drop down by degrees against the smart and steady breeze which carried away the sand and rubbish leaving the ore behind. They used to take the ore thus sifted to their houses where they smelt it into lumps of varying size and sell the same to the blacksmiths, who turned them into agricultural implements &c. It is reported that tools made of this iron would last considerably longer than those made of imported material.
Limestone — This is found in considerable quantities near Layam in the Tovala Taluq, Tirupurathur in Neyyattinkara and Kazhakuttam in Trivandrum. It is dug out from pits varying from about 5 to 8 feet and it is reported that limestone of a superior quality is obtainable at greater depths. The lime made here is chiefly sold to the Public Works Department. It is used for paving sides of wells and tanks and for making tubs.
Granite — The gneiss near Cape Comorin is generally like those of the Nilgiris but more quartzose. The Cape Comorin type of rock abounding in South Travancore is a well-bedded massive quartzo-felspathic granite gneiss abounding in small rich-coloured garnets. The rock also contains mica in glistening scales. Granite is used chiefly for metalling roads and erecting buildings, bridges &c. In the Chengannur Taluq which is noted for its excellent workmanship in granite, some good specimens of images, flutes, rose-water sprinklers &c. are made out of it.
The supply of beautiful building stones is practically unlimited in South Travancore but not much use is made of them except for temples and fort walls. The extensive Travancore lines are mostly built of gneiss, the Vattakotta Fort being a very fine sample of excellent well-cut masonry. To the extreme south end of the lines, blocks of marine sandstone have been employed in the walls to some extent but have been much affected by weathering.
Mica — This occurs chiefly in the Eraniel Taluk. It is worked by regular mining operations. The out-put for 1899 was 12,706 lbs. The following is an extract from a letter from Messrs. Henry Grail and Co., London, dated 11th May 1900 regarding the quality and quotation of Travancore mica —
“Several parcels of Travancore mica have been offered and sold here lately and to-day’s values are as follows with a good demand and good prospects for the future.
Travancore amber mica would come into severe competition with Canadian, hence the necessity of careful preparation.”
But the mineral has already become very scarce, the income to the Sirkar in 1903—1904 being only about 30 Rs.
Before concluding this part of the subject, it maybe well to state that according to the Royal Proclamation issued on the 14th June 1881 (2nd Mithunam 1056). Government have reserved to themselves the right to all the metals and minerals discovered on private properties. It has also been notified on the 30th July 1898 that prospecting for or mining of metals and minerals, whether in Sirkar or private lands, is strictly prohibited except under a license obtained from the Government in accordance with the rules in force for the purpose.