Rev J TENISON WOODS 

Published in The South Australian Register, Thursday October 1 1857.

 

It has sometimes been a subject of remark that Australia, for its size, is possessed of fewer volcanic evidences than any other country of equal extent. While Europe, not very much larger, possesses several which are even now in a state of activity, and is literally studded all over with extinct craters, this country, as far as it is at present known, contains none of the former, and comparatively but few of the latter. Probably, a reason will be found for this when hereafter the geology of this continent is more studied; and I feel convinced that it will be generally recognised that disturbance has been altogether less frequent in the northern than in the southern hemisphere. In the meantime we must content ourselves with close observation and a record of facts, feeling certain that theory and generalization will easily be accomplished when the hard work of detail has been got over.

 

With such a view I have to record my observations on the remarkable extinct crater named at the head of this notice; and I believe the particulars are interesting to science, not only on account of its being one of the most extensive known in this continent, but also because its description may serve as a guide in obtaining a knowledge of other volcanic phenomena in Australia. The ground has not been previously quite untrodden. Captain Sturt, as I am informed, made a series of observations on the place, but did not, as far as I am aware, proceed any further with regard to publishing his remarks. It is supposed, however, that he made some communications to Mr. G. P. R. James, and accordingly a rather romantic and incorrect account of Mount Gambier has found its way into one of the works of that novelist. In 1851 Mr. Blandowski surveyed and mapped the three lakes, and made some valuable mineralogical and geological observations. Part of the latter were embodied in a series of letters on the subject published in the German newspaper of this colony; but owing to the gold discovery and the confusion consequent thereon, the maps, etc., were, I believe, unfortunately lost. Nothing further has been done to give an account of this singular phenomenon of geology; and in order that something may be known, and to prevent many erroneous impressions which have gone forth gaining credit, I am induced to submit my own observations. I have not seen Mr. Blandowski's papers on the subject, and therefore cannot tell how far his views and mine coincide; but should any of my conclusions bear a stamp of less probability than any he has advanced, I shall be most happy to give way; for as my object is the advancement of science, and not my opinions, I shall always prefer a true theory to giving currency to any deductions of my own. I am sure of this, however, that the facts are stated strictly as observed, and as I have always given the reasons which have led me to draw any conclusions, readers can judge for themselves whether they are hasty or not. With this introduction, let me proceed at once to my observations.

The volcano, which is included in the general title of the mount, is a chain of craters extending nearly but not quite east and west, the wall at the latter side being much the most elevated. There are three lakes; but the centre one is (for reasons I shall hereafter give) not a crater, and they each possess such distinct features, that they require to be described separately. That on the east end, called respectively the Blue Lake and Lake Power, is a large and deep body of water of an irregular oval shape, surrounded on all sides by banks a couple of hundred feet high, and so steep that descent to the water's edge is quite impossible,  except in one or two places. The sides are thickly wooded, mostly with varieties of the teatree (melaleuca), excepting where the rough rock stands forth in perpendicular escarpments, and then the dark green brush is broken through by huge and craggy rocks descending precipitously to the edge of the water, whose already dark hue is rendered still more gloomy by the reflection of these black and stony walls. The whole appearance of this lake is wild and sombre in the extreme. The deep blue or rather inky appearance of the waters, which are withal calm and placid; the blackened precipices which bear so plainly the tokens of fiery ravages; the thick and tangled nature of the brush, give the place an air of savage loneliness. And then the spot is so quiet - so still, that but for the cawing of the rooks overhead, or the splashing of a solitary waterfowl, one might almost imagine Nature to be at rest, tired with sending forth those volcanic fires which poured forth ages ago.

The next lake is merely a good-sized pond, of moderate depth, but surrounded on all sides with banks as high as the last-mentioned basin. These banks are steep, but not precipitous, and in no case show large outcroppings of rock; they slope all round at an equal inclination, and are studded with the well known sheaoak (casuarina) and that species of honeysuckle which is, I believe, known in botany as the banksia integrafolia. The water at the bottom has only made its appearance (as I am told) within the last few years.

 

The third lake differs much from the two preceding, and is possessed of so many and varied features that it is difficult in the details of its description to give a good general idea of its appearance. It is nearly as large as the blue lake crater, and of an almost circular form, but the bottom is only partially covered with water, deep in some places and in others very shallow. Those parts which are left dry are always connected with the sides, though in one instance by a mere strip of land, and the ground is very undulatory, rising sometimes into hillocks which are some little height above the water. The water is mostly af each end and the ground in the middle, but by far the larger part of the lake is at the eastern side. In the dry part there occur two small ponds, which being quite circular, appear as if two wells had been sunk side by side. The crater walls surrounding this lake are very remarkable. At the eastern end they are lowest, rising gradually till about a third of the way round on the northern side, and then rising suddenly into a peak, and descending again for a short distance, again mount by a very abrupt elevation to nearly double the previous height, from which point there is a gentle slope upwards to the highest part of the mount, where the trigonometrical station is erected. From this there is a still more abrupt descent to the usual height of the sides, which is continued round to the starting point at the east side. That part of the wall which is so considerably higher than the rest is what is properly termed Mount Gambier. It is the higher wall of the crater, and gives a better key to the kind of eruption that has taken place than any other part of the mount. Standing on the highest point, one perceives a basin on the south side, which is called the PunchbowL It seems like a hollow scooped out by an eruption in the side, and at a distance appears precisely similar to the Cumbrecito in the side of the Caldera, in Palma (Cape Verd Islands). On nearing it, however, it is found to be very deep, so that its real form is like a funnel, with one side (that which is inside the lake walls) much lower than the other. Here a sort of pitchstone porphyry is very common, especially on the lower or inner side.

 

At first sight this would appear to be a crater on a very small scale; but as there is no sign of any tufa having fallen round it as from a centre, and as the soil is so deep on the inside, covered with long grass and fern, such an opinion would not be supported by anything except the mere shape. A little past the bowl, nearing the eastern side, the walls, instead of sloping down to the lake as heretofore, become precipitous, and the volcanic ashes disappearing from the sides appear only on the top. The precipitous portions of this end (forming at least half of the wall) are formed of the fossiliferous coralline strata peculiar to this district. The stratification is nearly horizontal, with a decided though slight dip inwards, which dip being quaqua-versal, or inclining all round to a common centre, shows tne rock to nave subsided into a hollow previous to the eruption, of which hollow, as will be afterwards seen, the present crater forms only a part, The water appeared to me to be deepest here. The strata are not in the least altered by fire, as far as one could judge from a short distance, the only change being a weather-worn appearance, which is observable in caves elsewhere. There is no channel or dyke in any one of the three lakes, such as would be made by a flow  of lava; indeed, there is very little appearance of lava in the whole group, but always between the coralline strata and the ash there is a layer of basaltic trap, very black and porous, which is rather thick in the blue lake, but only a moderate seam at the end of the valley lake I have been just describing. True lava is entirely absent, but a brownish semi-vitreous substance, porous and light, is found on the bottom and sides of the valley lake. On the sides near the higher wall, or mount, it occurs more frequently, evidently having streamed down in a backward flow to the point of ejection before cooling. Scoriae and ashes are common even far above the water line, but are not often found free from incipient decomposition.

 

To return now to a more minute description of those portions which throw a light on the mount, or higher wall. This is formed of successive layers of an ash conglomerate, composed of scoria, fragments of obsidian, porous lava, and pieces of the fossiliferous rock, all strongly cemented together into a very hard stone. The Wall is a mere ridge on the top, but sloping down on each side to a considerable thickness. The rock being undecomposed, the layers are well defined, and rendered still more conspicuous from the existence of a sort of buttress, which runs from the water's edge to the highest point. It is here observed that the layers thin out very rapidly, and are inclined at a greater angle in proportion as they near the summit. Thus the dip is constantly variable, but, what is somewhat remarkable, the stuke inclines at each side of the buttress, which latter comes out pretty considerably into the lake, and is matched on the other side by a similar promontory, making the ground plan of the lake somewhat like the figure 8. This fact is of importance, and, because as these two promontories make nearly a complete circle round the water where the volcano has left most traces, it would seem as if the eruption was confined to this end only - a circumstance which will seem more reasonable from what will be afterwards advanced. The activity of this part of the crater must have concluded with as great violence as the commencement, because at the very summit of the highest part there are two or three immense fragments of the fossiliferous rock imbedded firmly in the

conglomerate.

 

Thus far I have been merely describing those features which are calculated to elucidate the geology of the volcano. I must now consider from these evidences what kind of eruption has taken place to cause the appearances related. Let us take the valley lake first, as best fitted, from its peculiarities, to give us an insight into the whole phenomena. In the first place we must not regard the whole basin known as the Valley Lake as one large crater. The fact of the whole of the west end being formed of ashes and scoriae, whilst the whole of the east end is composed of fossiliferous rocks, undistturbed, and bearing scarcely any marks of volcanic action, is sufficiently indicative of this. The eruption of the crater was, in my opinion, entirely confined to the west side, and was neither, comparatively speaking, very violent nor of long duration. The greatest height of ash is probably not more than 500 feet, and this appears to have been formed almost  exclusively from the deep and irregularly formed lake which lies at the bottom of the higher wall, and this wall, moreover, is nearly the only remains which the  eruption has left behind to mark its progress. Of course the two little well-shaped vents for the middle of the lake, already alluded to, contributed their quota; but as they are both surrounded by a circular wall some 10 or 12 feet high (which makes them bear some analogy to the Mexican Trornitoes), one must regard their contributions as not on a very extensive scale. That the eruption of this lake was not very violent may be gathered from the following facts:- The tufa, &c, are not scattered very far, and do not seem to have been thrown to any considerable height, for the higher wall is so near the point of ejection, and so very narrow compared to the sides of the blue lake. Again, the strata of conglomerate thin out so rapidly, that they could not have been formed by a volcanic process on a very large scale. Besides, to sum up all to a self-evident proposition, if there was much thrown up, there would be more to be seen than there is at present. Many who have seen the mount will be surprised at its size being considered small; but when we remember that the volcano of Jorullo in Mexico was elevated considerably over 1,000 feet in a single night - when we remember the tremendous height of some volcanic mountains (Mount Loa, for instance, by no means tha largest, which is 4,000 feet high), we cannot think it would take very long to form a cone of the moderate pretensions of Mount Gambier.

 

Of course, when we speak of small eruptions and moderate, these remarks must be qualified by recollecting that any volcanic action is the result of a vast convulsion of nature, always attended with serious effects; and had there been any life or property in the neighbourhood of Mount Gambier at the time of its eruption, the results would doubtless have been quite extensive enough for the sufferers. But it may be asked how is it, if the disturbance was confined to one side of the crater,that the ejectamenta do not form a complete circle round the point of ejection. The answer to this difficulty, which required some investigation to solve, explains one of the peculiar features of the volcano, which is, I think, unparalleled in any other volcano in the world, and accounts for the fossiliferous precipice on the eastern end of the basin. The hypothesis, which after considerable enquiry, I have been induced to adopt is this:- Previous to the eruption, and after the upheaval of the rocks to their present position, a large circular mass of rock fell, in consequence of some failure of support underneath (probably an igneous agent), and an immense chasm was formed. Such a chasm would form an ample receptacle for all the ejectamenta which fell eastward without any way near filling it up. Such a theory as this receives every support from what is observed elsewhere; indeed it would never have suggested itself had I not observed the phenomena in other parts of the district. Thus, at a spot about a mile from the blue lake there is a place called the Cave Station, at which two immense basins of chasms may be seen, whose precipitous sides and many other evidences easily recognised show them to result from immense masses of rock having fallen in bodily. The friable nature of the coralline rock renders it much more liable to this kind of accident, and the country to some distance round is filled with  caves and funnel-shaped holes, which nearly all owe their origin to the same cause. That there was a subsidence at the valley lake after the upheaval of the strata is shown by the quaquaversal dip of the beds towards the centres of the basin, and that a chasm was eventually the result of such a subsidence is recognised from an identity of appearance with the caves, as they are called, just alluded to.

 

The existence, then, of such a chasm easily explains why the wall of ash does not form a complete circle round the principal point of ejection. The great disproportion of what I have termed the higher wall to the rest of the ash deposit must of course be attributed to the prevailing direction of the wind, which is always very violent during volcanic disturbance. For the air, heated by the boiling liquid below, rises rapidly, and cool air rushing in to supply the vacuum so caused gives rise to a current of air in one direction. This is the reason why, in the volcanic Island of St. Paul (38° 41' S., 77° 37' E.) the west side is 800 feet high, while the east is not much above the water's edge. But as the wind only accounts for a disproportion, and not for the total absence of one side, the theory of the chasm, which is only supposing what the appearance really bears out, is the only satisfactory explanation. I have one thing more to add. I spoke just now of two promontories which jut out from the walls and partially enclose the water. One of these promontories is the ridge I have described, which runs to the top of the highest part of the mount. The other is very remarkable. Seen from the east it appears like a succession of nearly horizontal layers of ash rising into a  straight thin wall, nearly 40 feet high, but seen from the peak it is found to be composed of strata of tufa dipping in towards the central point of ejection at an angle of nearly 60°. The fact of its having an inclination only one way, and that towards the west or highest part of the crater, is pretty conclusive proof that, at  the time of its formation, there was only one end of the lake from which ejectamenta were coming, and that was the western end. Before leaving the valley lake I must allude to the appearance on the southern side, called the Punchbowl, which I said was not unlike the Caldera of Palma; this perhaps due to a subsidence of the underlaying rock, either before the volcanic disturbance of which the ashes were loose. Such an appearance would be caused by either, for if there was a small cave there before the eruption they would fill it in the way it at present appears, or if by the failure of support underneath the ashes gave way, the appearances would be similar. Some subsidence has taken place since the deposition of the ashes, for on the north side of the basin, where the amygdaloidal lava is in greatest quantities, the ground sounds very hollow on percussion for some distance, showing the existence of some cave underneath, the hard nature of the pitchstone just there preventing its falling in.

 

Whatever theory, however, is adopted for the Punchbowl, must explain the middle or green lake, which, be it remembered, lies equally between the blue and the valley lake, for the appearances are almost identical in both. Where, it will be asked, did the seam of basalt come from which lies on the eastern coralline rock  underneath the ash? Probably from the blue lake, whence the ash also proceeded. And let me remark that this seam would favour the idea of the green lake having been a small cave before the eruption; for, had there been a seam of basalt in existence, it would, perhaps, have been strong eaough to prevent the subsidence of the ash after deposition. There are no signs, however, of basalt on the sides of the green lake, though, it appears on that side of the Punchbowl which is nearest the valley lake. And in reply to a demand as to how did this basalt come to its present position, it may be replied that there can be no doubt it was an ejection of trap through a dyke before the eruption - an occurrence common enough in geology. If, now, the cave was in the spot where the green lake now is, it would become in a measure filled by such on ejection; but being afterwards covered with ash, the basalt would become invisible. I shall hereafter have occasion to describe the whole course of the eruption, and I therefore shall give my reasons now for what would otherwise stand without proof. So let me add that the chasm of the valley lake was formed after the ejection of the basalt, because if it existed before, there would have been some marks of the trap having overflowed, and such is not the case. On the contrary, the trap is fractured even with the strata, and with the same marks of having been broken. Further,

a stratum of trap, if ejected from the place where the blue lake now is, would find its way to the place where the chasm of the valley lake at present exists in  spite of the cave of the valley lake lying between. Nor may we suppose it would necessarily have been filled up by the trap, for though it lies exactly between, it is small in comparison to either, and would have given ample facility for the basalt to have flowed round. Looking at the lakes as they at present are, this theory would scarcely seem feasible; but when it is remembered that the quantity of ash that has fallen has quite altered the configuration of the place, the difficulty is  removed. Nay, once suppose all the ash that is about to be cleared away down to the limestone strata, the truth of the hypothesis strikes one directly.

I have reserved to the last the consideration of the blue lake, as being the most extensive, and as where the eruption both began and ended. Having already described its aspect and appearance, I have only now to do with its geological features. From the regularity in the form of the walls,, and from their uniform height all round, one easily concludes that whatever eruption took place from this crater it was sustained from a line in the centre without being subject to any  variation. Indeed, the whole seems to have been formed by successive layers of ash regularly distributed all round on the top of the stratum of trap (much thicker here) which lies on the limestone,and through which the volcano has broken a passage. Close to the lake the ash is probably 150 feet thick; at a quarter of a mile this is reduced to between 40 and 50 feet; and the distance of a mile this thins out to a mere seam, varying from three to six feet in thickness, and so on, till it becomes lost in the merest band. This is what is perceptible about a foot or so from the surface; but as the dark soil of the country is nothing but the result of decomposed ash, the deposit must have been much thicker than it now appears. Nearly all around the lake there is a regular line of demarcation made by the thick seam of basalt which intervenes between the rock and the ash. The limestone strata is in many places blackened crystalline and devoid of fossils, but there can be no doubt from its regular stratification and union with parts that are fossilferous that it is merely altered by heat, and crystallized, though far too impure and siliceous to become marble. There are no incrustations of lava, no pumice or scoriae adhering to the sides, wherever I could examine them, and, as  far as appearances go, this holds good all round.

 

I must observe, however, that as some portions of the wall rise straight from the water's edge, they can only be examined by means of a boat. Descending to the margin of the lake (a proceeding which requires some little nerve and prudence to accomplish) the appearance of the water is quite changed. Instead of having  that dark and murky hue it seems to possess as seen from above, it assumes a beautiful crystal clearness, unequalled by the purest spring that ever flowed from a rock. Rapidly deepening from the side, the water becomes a delicate azure at a short distance from the brush, still in its faint distinctness showing the outlines of great boulders of rock on the bottom, whose great proportions are gradually lost in the increasing depth. And there the surface is so calm, and quiet, only disturbed by the most gentle rippling, which wreaths the pretty water plants into most graceful forms, and makes them from time to time reveal the surface of the snow-wliite rock upon which they grow. Sometimes, however, the water deepens perpendicularly from the sides. The lake is known to be 240 feet deep in the middle, and from soundings it would appear that the bottom is flat and equal like a floor. This was ascertained from a boat which took the Governor upon its surface - the only time its waters were traversed by man. I was unable to find any tufa, scoria, or porous lava, a few fragments of pitchstone being the only volcanic evidences which appear. This may not be the case all round, but until more facilities are afforded for investigation my conclusions must rest only upon what I am able to observe.

Here then the evidence shows there has been an eruption which has been considerable, both from the size of the lake and the immense quantities of ash thrown to such a distance. That it has been accompanied with violent explosions is seen from the immense masses of basalt which are sometimes buried in the ash; and yet with all these marks of disturbance there are no signs of any outpouring of lava, little or no pumice or scoriae, and not even an aperture in the side through which any lava could have flowed, nor any fragmentary slags adhering to the face of the precipitous rock. Such appearances, seemingly contradictory and  inexplicable at first, are consequences of the peculiar nature of the eruption which took place. I am going now to give a history of the igneous activity of the volcano, which will clear up whatever obscurity there appears to rest on the mode of its disturbance, and as I proceed along I shall give the complete chain of evidence by which the explanation is supported; but as the theory would appear startling unless some parallel case were cited, let me by way of preface give an account of a volcano at present inactivity which Mount Gambier most resembles. In the Sandwich Islands there is a volcano called Mount Loa, which, though very much larger than the one under consideration, resembles it in many ways. In the side there is a lateral crater (at present in activity) called Kilanea, which is 3,970 feet above the level of the sea, or about the same height as Vesuvius. Sir C. Lyell, in his admirable "Manual of Geology," describes it thus:- "Kilanea is an immense chasm 1,000 feet deep, and in its outer circuit no less than from two to three miles in diameter. Lava is usually seen to boil up from the bottom in a lake, the level of which alters continually, for the liquid rises or falls several hundred feet, according to the active or quiescent state of the volcano. But instead of overflowing the rim of the crater, as commonly happens in other vents, the column of meIted rock forces a passage into subterranean galleries or vents leading towards the sea." A Mr. Coan has described an eruption which took place in 1840, when the lava had risen high in the crater and began to escape from it. The direction of the current was first traced from the emission of a bright vivid light from an ancient crater 400 feet deep, about six miles to the eastward of Kilanea.

 

The next indication was about four miles further on, where the fiery flood broke out, and spread itself over about 50 acres of land, and found its way underground for several miles further, to re-appear at the bottom of another ancient crater, which it partly filled up. The course of the fluid then became invisible  for several miles, until it broke out for the last time 27 miles from Kilanea, running in the open air for 12 miles, and then escaping over a cliff 50 feet high, and forming a cataract of liquid fire into the sea for three weeks. The termination was about 40 miles from Kilanea. Now, there can be very little doubt that something similar to this has happened at Mount Gambier, consequent on the eruption, perhaps, of both craters. The mount is scarcely 15 miles from the sea, and being not much above the level of the latter would not give occasion to the lava to come to the surface during its passage. Mount Shanck, another volcano, lies in the  straight line between the sea and Mount Gambier, but not having examined it, I am unable to say whether or not it is entirely caused by a passage of lava. This theory was formed after investigating the features of the blue lake, for it seemed quite natural to conclude that after such an eruption there must have been a flow of lava in some direction, and I was sure, if the hypothesis were correct, and provided the sea level had not much altered since the eruption, there should be some signs of volcanic rocks on tha sea coast. To my great gratification I have since been informed by a gentleman who knows the place well, that along the coast for some distance the fossiliferous cliffs are, as it were, based upon a thick stratum of basalt, which spreads down to the sea. A more complete verification of a theory could scarcely have been expected, and I think we may not unreasonably regard it as fairly established. The eruption then was thus:- the boiling lava, from whatever cause arising, before it had formed a vent, forced up a column of liquid rock, which spread itself over the surface in the form of a thick layer of trap in the spot now occupied by the lakes. The pressure which would force up a column of lava at least 240 feet must have been enormous, and this, when exercised on the soft friable rock of the sides, or it may be on what is mere sand (underneath the coral strata), when combined with heat, would easiy force a passage towards the sea; and once an outlet was obtained, the absence of lava would cause a hollow, and finally a chasm, through which the eruption of ash  would have full play. To a failure of support, consequent on a subterranean outpouring of lava, I attribute the chasms of both the blue and valley lakes, with this difference, that, while the eruption continued throughout the whole extent of the blue lake after the falling in of the rock, in the valley lake it was confined to the west end of the chasm, formerly the high wall or peak of Mount Gambier. The eruption, then, of the blue lake was simply limited to the ejection of large quantities of ashes and occasional fragments of rock, continued for some time after part of the boiling fluid had made a way under the soft limestone rock, and flowed down to the sea. 

 

There were, I think, three periods during which the blue lake crater was more active than at other times, though the lulls apparently were only temporary and far from leaving the mount in a perfect state of repose. The following are the reasons upon which these suppositions are based:- At a short distance from the lake the ashes are found to lie in three distinct layers, all composed of coarse tufa underneath, and fine ash dust on the uppermost side. Each layer was doubtless caused by a distinct violent eruption, which on the commencement would scatter large fragments about, and as the energy subsided a fine ash dust would gradually cover them over. The eruption again breaking out, would renew the large fragmentary layer, thus marking its own periods of disturbance by distinct strata.

That the walls were only very temporary may be seen from the fact that the fine dust on the upper side of the lower or of the middle strata had not time to become the least altered before the second and third deposits were superimposed. Generally above the upper layer there is a mass of rich black loam covering it at a variable thickness. This is decomposed ash, originally of a fine and therefore easily decomposable texture. This latter deposit is easily accounted for, because after an outbreak there ensues, in all volcanoes, a long period of quasidisturbance, during which time the eruption is, as it were, settling down and the crater cooling. In this interval smoke and fine dust are continually emitted, and cover the ground to some extent thicker in those places nearer the crater.

There remains now only one point to be noticed, and that is as to what geological date we are to assign the period of disturbance. One thing only is certain, that it happened since the secondary period, though at what precise epoch there is no evidence to show. Tho fossiliferous rocks so often alluded to are of the upper  secondary; but I fear I have been too premature in assigning them to the cretaceous, as many fossils I have since met with make it doubtful whether their proper place would not be in the oolite, probably coeval with the coral rag in Oxfordshire. I have many reasons for supposing also that they are of the same formation as the Murray beds where the bones were recently found. In any case, the ashes are resting above them, and evidently there has been little or no upheaval since the volcano broke forth. They were formerly, beyond a doubt, part of a coral reef; and the immense ridges of coral which may still be seen are of a species not at present existing, nor, as far as I am aware of, any yet classified. Of the peculiarities of the strata, however, I shall say only one word more at present, so as not to render this description too long, and because I intend to devote another special paper to the fossils and formations of that district. Wherever the beds are found, caves also appear, many of which (by piles of bones, &c.) are seen to be certainly not later than the Post Pliocene. The rocks, therefore, were in that period in the position they are at present which they were also in when the volcano broke out; so that if hereafter caves should be found with ash, &c., inside, or bearing marks of having been disturbed by the eruption, some better approximation may be made to the geological date, but at present the rocks cease to guide us further.

But was the volcano in activity lately? An answer in the negative may safely be given, because, first, the ash is quite decomposed in many places, and the porous lava partly so, which must have taken considerable time to effect; and next, the large crater is filled with water to the depth of 240 feet, which water could not even have begun to collect until the rock was perfectly cool, and then must have taken ages to become the large body of fluid at present resting there. To give an idea how long it takes volcanoes to cool, or for the ash to decompose, I will mention a few instances. The lava of Jorullo, which poured forth in 1759, was found to retain a very high temperature half a century after. The ashes on the Peak of Teneriffe are nearly undecomposed, and yet it is not known to have received any fresh additions during the last 600 years. Some of the ashes on extinct volcanoes in Aurergne, which I visited in 1853, are much less decomposed than those of Mount Gambier, and yet the former have been deposited more than 1,800 years ago. Now when it is remembared that the ashes of the latter are not only decomposed, but that large trees have taken root and grown up in it, we must be of opinion that our volcano has been extinct for some considerable time. And let it be remarked that the cases I have mentioned are not exceptional, for I could specify many more, which would all bear testimony to the antiquity of the mount.

I forgot to mention that there is always found between the ash and limestone, when at any distance from the craters, a thick bed of fine soil, showing that, after the upheaval of the reef from the sea, it became a sandy desert previous to the igneous outburst.

The minerals found in the craters are few, chiefly confined to a non-vitreous obsidian or pitchstone, and a green vitreous semi-transparent stone, which frequently contains, disseminated through it, crystals of hornblende and olivine. The latter mineral, or greenstone, as it is here called, I found, after a careful  qualitative analysis, to consist of silica, alumina, magnesia, sesquioxide or iron, and a trace of lime. The aborigines use the pitchstone as a weapon, fixing it in pieces of wood, and forming a kind of axe; and, singularly enough, the same mineral serves a similar purpose to the Indians near the Cordilleras of South

America.

 

I think I have now gone through the principal features of this curious volcano, in which I have often been obliged to sacrifice for succinctness many details I could have wished to have mentioned. We are told there is a philosophy in stones, and it certainly is strange what a history of the past a few rocks can give us. There has been a coral reef, a desert, and a burning mountain, where beautiful lakes now rest, and each period has erected monuments to its memory. There is a history too, written in plain characters for the mind of man, and my occupation has been to decipher it. Going back in imagination to the time when the coral was alive, and covered by the sea, who could have thought it would come to be what it. is now. But imagination is not needed. We have only to glance at the remains before us to realize the truth of the tale they tell. These rocks were once covered by the green waters. There, while the rising tide dashed its sparkling waves through the groves of coral, where the busy polypi were plying their variegated arms in search of matter to add to their structure, a thousand fishes frisked for a while, to die and leave their forms imprinted on the stone, while the cunning saurian slept among the arborescent forms or wilily watched his prey. Then the earth slowly raised them from the waters and life faded away. Fishes and reptiles are gone, and stones tell how they lived and died. The reef became a sandy desert, without a drop of water or a sign of vegetation to relieve the eye - a vast and dreary solitude. But Nature soon changes the scene. Subterranean thunders are heard - earthquakes rumble and rock the ground. Then masses of stone fall in and give vent to smoke and steam, which rush from the centre of the earth. By-and-bye fire begins to appear, and Nature, no longer able to restrain the ravages of heat, sends it forth into a bubbling hissing cauldron of molten  stone. Standing upon the brink (if human being could stand alive on such a place), while the air is darkened with smoke and ashes, and huge fragments of stone are being hurled into the air to fall into the hissing seething mass below; while the light from the fire and the noise of explosion blinds the lightning, or outbids the thunder overhead; while the bellowing and splashing of a lake of fire makes a scene at once horrible and magnificent, one could almost imagine oneself on the brink of Tartarus.

 

But comparison would be vain; not even Vulcan could stand and describe such a scene. He might have thought -

   "In Chaos antiquum confundimur . . .

     . . . neque eniun tolerare vaporem

     Ulterius potuit, nce dicere plura." - Ov. Phoeton.

 

But now how changed is the scene! The smoke has cleared away and the fires are extinct. Nature is at her repose. The melted walls have cooled, and an azure lake covers them. The ashes on the bank are covered with verdure, and reeds grow where fire glowed. The underground thunders are indeed heard no more, but the wind sends a soft moaning through the shrubs, while the gentle [s]plashing of the calm and glassy lake is now the only echo that is heard from shore to shore.

 

J. E. W.   Penola, September 24, 1857.