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earth opening on them, and others were drowned by the sudden irruption of the waters of the ocean."
On the 18th April, 1818, another violent earthquake was experienced on the west coast. Sir T. Rafles, who arrived at Bepcoolen the day after, found that every house was more or less shattered, and many in ruins. In the Island of Pulo Nias, on the west coast, earthquakes appear to be felt very severely. The same remark may possibly apply to the other Islands in the same chain, for our knowledge of these phenomena in the native countries has been hitherto almost entirely accidental, and our information regarding Pulo Nias arises from the connection of Europeans with it. Marsden mentions that in 1763 a village in that Island was swallowed up by an earthquake, and a recent shock, which will be immediately noticed more at large, was still more disastrous in its effects. That the undulations in most cases extend across the straits to the semi-volcanic line is highly probable. Although our connection with the straits now extends over a period of 60 years, unfortunately no connected records have been preserved of the critical geological and meteorological phenomena that have been experienced during that time. In Pinang during the last 12 years several shocks have been felt. These occurred in November 1833, August 1835, September 1837 and January 1813. *
Those of 1837 were the most violent, and the undulations appear to have been from south to north, and to have lasted a minute and a half. The shocks in 1843 happened about half an hour after midnight on the morning of the 6th of January, and at } past 2 P. M. on the Sth. The
* Pinang Gazette of 7th, 141h and 28th January, 1843.
+ " It is said that on that occasion several herds of cattle in the neighbourhood were observed running in the utmost confusion in all directions, that lamps and picture frames oscillated, that the Roman Catholic Church bell rang of its own accord, that quantities of large shot piled up in the Fort were thrown down and scattered about, that a stone wall of a substantial building in town was rent, and that the whole inhabitants were thrown into a state of consternation. The shipping in the harbour did not experience this shock, nor did the sea appear agitated. Fise days subsequently, however, another smart shock was felt and was followed by a very heavy squall from the N. W. and great agitation aud rise of the sea in the harbour. The tides overflowed the Northern beach, and Hood. ed the compounds and lower rooms of the houses in the neighbourhood. This convulsion was experienced about the same time at Acheen and along the Pedier coast, and it is said that these places sustained considerable damage.” Pinang Gazette of 28th January, 1843,
first shock was more severe than the second, but both were slight, producing no other mechanical effects than a tremour of the ground which caused articles suspended to oscillate, stopped a clock, and occasioned in some persons a giddiness in the head. The first shock although only felt by a few persons in the plain, who happened to be awake, caused the residents on one of the hills to spring from their beds under the apprehension that robbers had attacked their houses, so violent was the noise of rattling venetians, bolts, &c. The undu. lations on this occasion, as in 1857, appeared to be from south to north. The shock on the morning of the 6th was experienced precisely at the same instant at Singapore* and at Malacca.† The undulations at Singapore are said to have been from east to west, very slight, and to have lasted 8 or 10 seconds. About half a year afterwards it was first learned in the Straits that a most violent earthquake had devastated Pulo Nias, commencing about midnight, between the 5th and 6th January, or nearly the same time when the undulations were felt along the western coast of the Peninsula. The shocks were at first from the west, shifting to the north, but as they increased in violence they appeared to lose any fixed direction and became a complete trembling of the earth, which lasted 9 minutes; houses were destroyed, trees uprooted, a portion of a mountain fell, and the ground opened in wide fissures, from which “a black frothy liquid trickled.” After a brief interval of inaction, the undulations recommenced and the sea suddenly rose in a vast wave which rolled in from the south-east, overwhelming a considerable tract of country and sweeping away whole villages and their inhabitants. The shocks were felt at intervals of 2 minutes until į past 4 in the morning, when another paroxysm even more violent than the first took place, lasting about 6 minutes. The shocks were from the west, veering to the north, but changing directly to the south. Tremours of the ground were experienced for several subsequent days. Thus the latest earthquake that has occurred in this region was experienced in its greatest violence a little to the west of the volcanic chain of Sumatra, and the undulations were transmitted or induced so widely and so rapidly as to reach Penang, Malacca and Singapore simultaneously and at or about the same time when the first shock was felt at Pulo Nias, It appears therefore that the volcanoes of Sumatra still communicate Singapore Free Press of the 12th January, 1843. + Id. of 2nd February, 1843.
with an internal igneous sea, and from time to time emit smoke and gases, that to this day the Island is subject to frequent earthquakes, that several of those that have occurred within the last hundred years have been of great force, rending the ground, and at least on two occasions giving vent to liquid volcanic matter, and that their operation extends, though with diminished violence, to the western coast of the Peninsula. When we consider the height and bulk of the crateriform volcanic mountains even viewed only relatively to the level of the hilly country above which they rise, and the large belts of volcanic rocks which exist in the neighbourhood of some of those that have been explored, if they do not connect the whole chain, we are carried back to a period in the history of Sumatra during which its volcanic phenomena were on the grandest scale. If at this day, when the fires of her mountains have ceased, or are dormant, the coast of the Peninsula is agitated by the comparatively feeble shocks which disturb the repose of the Island, it is reasonable to believe that when her volcanoes, whether simultaneously, successively, or alternately, were in full activity along a line of nearly a thousand miles, the neighbouring regions to the distance of 100 to 200 miles must have been subject to earthquakes of great violence, and accompanied, according to the degree of their intensity, by volcanic emissions and eruptions in greater or less abundance. That portion of the volcanic belt where the evidences of violent igneous action are most striking, appears to be Singapore, and the neighbourhood, although it is not improbable that the whole tract from Cape Rachado to Banca, exhibits more extensive and continuous disturbance than the northern part of the belt. That region of Sumatra which, so far as observation has extended, may be termed the principal volcanic tract, is about 3 degrees distant from Singapore, and lies in a parallel about a degree and a quarter to the south of this Island. The direction of the Singapore strata is across or approximately at right angles to parallel lines forming the sides of a plane connecting the Island with this part of Menangkabu, and the dip of the strata although, as formerly observed, exhibiting much irregularity, is generally from the point of the compass where Menangkabu lies.
There seems, upon the whole, to be strong grounds for the opinion that the hill system of Singapore has its volcanic* connection with
* Our meagre information regarding the formations of Sumatra does not admit of our instituting a comparison between them and the rocks of the opposite coast of the Penin
Sumatra and not with the mountain chain of the Peninsula. If this view shall be found to be borne out by further observations, we must conceive that the old granite mountain chain of the Peninsula (which, as is shown in the paper before mentioned, terminates apparently between Parcelar Point and Pulo Varela, although a few minor groups exist in the interior to the southward) had its extremity in this direction washed by the sea. The region below which operated the expansive volcanic fluids or gases whose effects we are considering, extended from Sumatra to the Peninsula, and probably a little to the westward of the one and considerably to the eastward of the other, for the whole vast platform or partially emerging and partially subsiding continent that rises out of the depths of the Indian ocean and stretches eastward far into the Pacific, rests on one region of connected though shifting subterranean excitement. The line of most intense force would be the ordinary one, the volcanic chain of Sumatra. Thence the waves of the volcanic sea would travel in parallel lines to the north-eastward, causing a tension of the region and a tendency to split in the direction of those lines. That portion of the region intermediate between the western and eastern mountain chains which had not been disturbed and fractured during the process of elevation like that from which the chains were obtruded, or of which the fractures had not reached the surface, would offer most resistence. But on arriving at the western limit of the old fractures caused during the elevation of the Malayan chain, the space so fractured would yield in various points of weakness. The old fractures at the southern extremity of the chain would, by the tension, be prolonged in the same direction, that is to the S. E., and cross fractures being established and the vol
sula. The central mountains are chiefly plutonic and volcanic. The granite or sienite of the southern regions would appear from Marsden's slight notice to resemble that of Singapore. The lower tracts of the west coast as described by him possess a remarkable resemblance in their general configuration to the surface of Singapore. Like the latter, they consist of rounded elevations of no great height, separated by winding flat swamp3 penetrating for miles between them. The hills“ not unfrequently exhibit the appearance of an amphitheatre.” A co-incidence in a configuration so uncommon when other analogies are also considered, can hardly be viewed as accidental. The soil he describes as a stiff reddish clay. The rock exposed in sea cliffs and in some places at the bottoms of rivers is a species of clay called by the natives nappal, which is common in Singapore. The country between the mountains and the eastern coast of Sumatra is little known, but what information has been oblained respecting its geological features I have collected in the paper before alluded to.
canic forces sufficing to elevate the rocks and produce eruptions at different places along the lines of fissure, the system of semi-volcanic hills extending from the termination of the Malayan plutonic chain to Banca would be produced. Whether we admit the notion of a translation of waves or suppose that under the region a general volcanic pressure was in operation, producing an expansive tendency whose superficial manifestations varied according to the mineral structure and composition of the rocky crust and particular local intensity of force, the same results would follow under the assigned conditions.
Having in the above paper had occasion to bring together several scattered notices of recent volcanic action in Sumatra and the west coast of the Peninsula, it may be remarked that some general facts appear which it may be useful to separate from the local matters with which they are mixed up.
1. The advance of a great wave upon the land, is a circumstance common to most earthquakes on sea coasts.
Mr. Darwin considers it to be caused by a line of fracture being formed beneath the sea. If there is a consequent sinking of the sea bed along the line, the rush of the waters on both sides to restore the level would occasion first the retirement of the sea from the shore and then the production of a wave rolling in upon the shore. But might it not also be caused without any sinking or even rending of the sea bed? A strong blow beneath the earth's crust imparting a momentary centrifugal tendency would cause the sea above the point or line of impact to rise violently to a height proportioned to the force of the concussion. But this wave would necessarily be partly above and partly below the general level, or have a hollow on each side towards which the neighbouring waters would rush, and thus the same effect be produced along the adjacent coast as in the former case. Mr. Darwin also mentions that places situated on shallow bays suffer great damage from these waves, while those seated close to the edge of profoundly deep water escape. In the same manner the waves of the Indian ocean, on reaching the shallow coast of Sumatra, rise as they advance until they acquire a great height. This is probably attributable to the friction of the bottom retarding the waves while a constant succession press on from the sea behind. When bays are narrow the wave will have a greater tendency to rise