Adelaide Philosophical Society

SUBJECT - "THE GEOLOGY OF THE SOUTH-EAST."

PAPER READ BY the REV. J. E. TENISON WOODS. F.G.S.. &c., 1866.

Followed by the paper being reviewed , by His Honor Mr. Chief Justice HANSON.

A paper was read before your Society on the 6th March last on the above subject. The author was your eminent associate, His Honor Chief Justice Hanson, who raised some points which, he said, were open to discussion. I think I shall be com­plying with the objects of your Institute by follow­ing up these questions. I shall at the very outset state that I differ from some of the conclusions drawn by His Honor; but as he, in common with the rest of the members, has no object but the elucidation of truth, no apology will, I trust, be due to him or you on that account. I should wish, however, to place on record my appreciation of the spirit which actuates him in these researches, and to express my sense of the terms of approval in which he refers to my previous labours. Coming, as they do, from a fellow-labourer who can, I am sure, estimate the difficulties and intricacy of the subject, such applause is very gratifying and en­couraging, even though His Honor considers that some of my conclusions may require modification. His Honor first refers to my opinion that at the time the "crag" of Guichen Bay was deposited the great body of the land lay to the northward, and he goes on to say that it might equally have been to the southward. But as I accounted for the tropical character of the fossils by supposing the land to be confined to warmer climates at the time, he explains how, in his opinion, a warm sea - that is to say, a subtropical sea - might occur even were the land confined to where he supposes it. On this subject I must make two observations. First, it is not from the tropical character of the fossils alone that I suppose the inter-tropical land to have existed in our tertiary era. The whole series of events from our Eocene period upwards shows that the land whence our Tertiary fossils were derived was north of the present south coast, and probably connected with land within the tropics. To give the proofs of this, drawn from physical geography alone, would he a long task, but a few instances of the geological proofs will suffice. The facies of our pre-Pliocene fossils is Philippine and tropical. The few existing species among them are found, with one exception, not to the south, but in the Chinese Seas. The changes effected in our older granites, schists, and diorites of the Cordillera point them out as existing as land within a great part of the older Tertiary period. Finally, to suppose land in the south during any of the Tertiary periods would be a gratuitous supposi­tion for which we have not a tittle of evidence, would be out of harmony with the present physical structure of the continent, and difficult, to reconcile with the changes which we know to have since taken place. I refer members to Mr. Selwyn's reports of the Victorian Geo­logical Survey for ample proof of what I have new stated. Secondly, I do not think that land to the southward would produce the effects which Mr. Hanson supposes. It certainly would depend very much upon where the land was situate. However, we may judge by the effect which Tasmania produces upon the fauna of Bass's Straits, and we can certainly say chat the land there does not favour the growth of a tropical fauna. The shells are more arctic in character than are to be found upon any other portion of the south coast. From this feature alone I can tell at a glance a collection made in Bass's Straits, and it is a singular fact that the influence of Tasmania extends as far nearly as Port MacDonnell, causing shells to subsist in those latitudes which would otherwise never be found there, nor in any other but a more southerly and colder habitat. On the other hand, Western Australia is sub-tropical in its molluscan fauna. East Indian shells; and even Red Sea species are found there, and the sub-tropical character extends round to King George's Sound, or a latitude only four degrees north of the place to where the sub-arctic influence of Tasmania extends. Again, as a proof of what the former state of things was, I may state that it is not at all uncommon to find Western Australian shells in our Pleistocene deposits; and nearly all the commonest fossils in such southerly places as Warrnambool are only found existing either in Spencer's Gulf or the Australian Bight. I am stating now what I know from my own observations, extending over some years, during which thousands of shells have passed through my hands. The Chief Justice next mentions a formation which he observed in Guichen Bay, and which he thinks had escaped my atten­tion. He describes it as a low cliff of dark scud, very different from ordinary sea-sand, with sea­shells in regular lines, showing that it was depo­sited in a sea in which these mollusca could live. At first His Honor was inclined to refer the sand to some active volcano, which had poured ashes into a sheltered arm of the sea; but subsequent remarks from Mr. Smeaton induced him to aban­don that opinion - very properly, I think. Shell­fish could not live in volcanic ashes, though they might have died there. But in all the deposits of marine volcanoes which I have examined in Southern Victoria I have not found any shells, either mixed up or in regular layers. However, shells or not, there is no volcano visible near; and supposing this bed to have been brought (as ashes sometimes are) some 80 miles from the nearest volcanic craters, it must have been something curious to leave a deposit 10 feet thick in one place, and to leave no traces anywhere else. But to shorten the argument, this sand, in my opinion, does not bear any resemblance to volcanic ashes, and, when examined, I can positively affirm is found to have no connection whatever with volcanoes. But if not volcanic, what is it? Mr. Hanson suggests that after the formation of the crag deposit, the whole district formed the shallow bed of a sea of nearly equal depth, which was unequally though very slowly upheaved, and that those portions which are preserved are fragments which were protected from the action of the waves, otherwise they must have been washed away, for the sand is so loose that even the wind has destroyed a great part of it, and left only the shells behind. From all this I must say, with great deference, that I respectfully dissent I know the deposit well, and did not overlook it in my work, where it is included among the sub-aerial deposits; but as I could not of course refer to every cliff on the coast, no special mention is made of this particular one. But I repeat I knew it well, and can mention some curious particulars respecting a portion of it which even Mr. Hanson did not remark. First, let me say that I do not regard the deposits as having been derived from the sea at all. They are in my opinion only sand-hills which have been drifted with vegetable matter into the places where they are found, and the lines of shells are the marks left by each successive surface. But in all this I am merely giving my opinion, which, if open to question, the facts I shall now relate are not. The contained fossils are principally Turbo undulatus, Lam., and Purpura textilosa, Lam., which do not live in a shallow sandy sea, but on a rocky coast. They are both of existing species, and from their peculiar appearance as fossils - an appearance known to naturalists as "dead shell" - must have been long exposed to the air, and nearly bleached before they were entombed. This alone would ex­plain the origin of the beds; but if other proof be wanting, I can refer enquirers to a good section underneath the old flagstaff; near the Robe Hotel. There not only is the subaerial character of the deposit seen, but also its very recent character. Buttes are to be found combined with the shell, and these bones are of such domestic animals as sheep and cattle. Occasionally a broken bottle may also be found with pieces of broken plates of very modern willow pattern, old shoes, and pieces of hoop iron. Such remains, of course, put time re­cent subaerial character of the beds beyond all question, and oblige us to abandon the theory of the tranquil shallow sea and slow upheaval. These modern fossils of domestic associations do not ex­tend to the bottom of the cliff; but quite sufficiently far to show the very modern date of the whole. The character of the shells show the same fact. They are mostly of a sort eaten both by natives and white people, and are found strewing the surface all about the town. This would account for their unworn, sharp, and well-defined forms, without supposing "some land to have existed where the open sea now spreads to the south and west." Indeed, I hardly know how we should find room for all the changes required by His Honor for the formation of this small deposit, and fortunately an easier explana­tion is at hand. I am glad to find that His Honor agrees with me in regarding the limestone stalactites, which look like roots, as concretions formed by infiltration. In this he also agrees with Mr Jukes, the emininent Director of the Geolo­gical Survey in England, who says, speaking of this formation at Perth, Western Australia:- "In other places are seen rising from the sand what appear to be trunks of fossil trees, having not only the external form of trees, but much even that resembles their internal structure. These occur throughout the colony wherever this white sand is found, and they have been frequently described at King George's Sound, where Mr. Darwin believed them to be calcareous concretions formed in the hollows left by decayed trees. In a cliff near Fremantle, however, near the entrance of the swan, I saw some of these deridritic masses fully exposed, and from their peculiar structure and conformation I believed them to be nothing more than stalactites formed in the sand by the percolation of rain water dissolving and taking up the carbonate of lime found in the sand, and re­depositing it in fantastic forms wherever predis­posing cause happened to determine it. I be­lieve the limestone in these sands to be formed in the same way, as the bedding had frequently a rather highly inclined or contorted dip, evidently not due to movements of elevation, but the result of their original formation. In this case I suppose rain to have sank through the sand, dissolving the carbonate of lime in its passage, till it at length became saturated, or could sink no further; and that as it evaporated, the carbonate of lime was deposited in a crystalline condition, binding up all the adjacent grains into a more or less solid stone." Jukes' Phy. Struc. Aust., p. 61. The italics are the author's. Mr. Hanson mentions four distinguishable formations, the lowest of which did not appear to be stratified, and had no concretions in it. Properly speaking, however, there is no true stratification in the whole of the concretionary rock. "False bedding," as it is termed, predominates in it all, and sometimes gives an appearance of a dip, which the beds do not in reality possess. Guichen Bay, however, is not the best place for examining this peculiar rock. At Cape Bridgewater and Cape Grant, near Port­land, it is seen in very fine bold sections of hard texture. At Point Lonsdale, also, those rocks are to be seen which formed the subject of Mr. Daintree's beautiful photo­graphs in the geographical reports. Indeed, the beds can hardly be fully understood without a close attention to their various appear-

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ances from Gipps Land round to Spencer's Gulf. After a careful study of the geological features of the cave at Mount Burr, Mr. Hanson is of opinion that there is evidence of a subsidence having taken place since the bone deposit was formed. I do not wish to detain you with the argument, but I will state briefly what I regard as the sequence of the events which placed the bones at the top of the entrance to the Mount Burr caves. Right in front of the cliff in which the cave occurs there is a swamp, which now drains at the end which is furthest from the cliff. But this drainage is a very recent one, and a very little would dam the swamp up again, and it would then have no outlet except at the foot of the cliff. Well, it is evident that it did drain in that manner quite lately to my know­ledge, and as a careful examination of the ground will show. I cannot stop to enumerate the appear­ances, but I may state that there are in this dis­trict several instances of swamps which drain under limestone barriers, and that the appear­ances there are just such as occur here. I will mention only one, which any one can examine. The slightest comparison between the Mount Burr cave and the place where the Avenue Swamp drains under the limestone at the old Avenue Crossing, will show that the pheno­mena are the same in both cases. But when the water at Mount Burr drained in this manner it had a very intricate passage to filter through, and there­fore bones, &c., would collect at the foot of the cliff; just as they do now at the old Avenue, and would form in like manner that peculiar red con­glomerate known as bone-earth. In the course of time, however, the water would wear for itself a wider and deeper passage, cutting through the bone earth as well as the stone underneath it, and as it gradually worked down its channel the bone deposit would be further and further above the level of its waters. This I conceive to be the reason why the bone-earth occupies so high a level, and if I am right it is the smallest portion of the deposit and the poorest in fossil remains. The greater portion has been carried in to the present bottom of the cave, where, if a trench were cut, a rich deposit of bone-earth would be found. I do not think that there is any evidence of subsidence, nor can I see how such evidence could exist without conflicting with geological appearances in the rest of the district. The forces of subsidence and upheaval should not be called in to explain every little feature which seems to require it. No doubt it is an easy way of getting over some of the operations of nature; but possibly nature has been more sparing in such movements than theories at present seem inclined to concede to her. I think, however, that a large and comprehensive view of her operations, not only in this district, but on the south coast generally, makes us timid of calling such movements to our aid in every little phenomenon, because we find anything like a harmonious system of geological change, such as we are forced by larger experience to adopt, then becomes impossible. It would seem to me, too, that Mr. Hanson believes that at one time the sea ran into this cave, or, at any rate, beat near the cliff when the cave was there. I speak with diffidence upon this point, because to me His Honor's statements do not seem clear. If it be the case that I am Wrong, what I sin about to say will be of course unnecessary. I have not met such evidence as would induce me to think that the sea ever entered this cave. The evidence re­quired would be recent sea-shells mixed up with the bone-earth, and a general littoral aspect in the detritus round. There is no such thing, as far as I know. Further than that, I believe that this rock was dry land during the whole of the Pleistocene period, and that the cave was hollowed out entirely by fresh water. At about 15 miles west of this cave Pleistocene shells may be found, but at a much lower level. I may add further that Pleistocene strata are so recent and so well marked that I do not think any portions of them have been denuded away, and that where none of its shells are found its waters could never have extended. At the same time I do think that the Mount Burr cliff in question was probably partly formed in the Pliocene period, but the cave did not exist then, as the fossils belong to a more modern epoch. It will appear, I daresay, to many of your members that I am taking much for granted, and dealing more in mere assertion than in proof, when I venture to differ from the Chief Justice upon these questions. Some of the facts, however, will speak for them­selves, an there are others which I cannot allege without extending this paper beyond all reasonable limits. I am not, however, treating of a matter which is new to me, nor dealing with facts that have not been carefully considered over and over again, besides being compared and collated with the labours of the geological survey in Victoria. For nearly ten years have I been more or less in contact with the phenomena which are now under discussion, so that they have become familiar to me in all their aspects. Nor would I differ from Mr. Hanson nor object to having my conlusions disputed were it not that he tells you his only opportunities for observation were his walks round Guichen Bay and his visit to Mount Burr, and were it not also that I am sure he will be pleased at anything which tends to elucidate the truth. I cannot close this paper without expressing my gratification at the accurate way in which the granites and schists at Encounter Bay are described in the conclusion of the paper. Any one could tell from its perusal, that His Honor was in presence of the half transmuted schist which extends from western Victoria to the Murray. It proves that this granite is a meta­morphic rock, but that the metamorphism was only partially accomplished in some cases, so that veins of the original rock still remain in the form of schist. It is not known whether this schist is the same which underlies the older rocks of Tasmania and Victoria, or whether it be a different formation. Its identity is, however, highly probable, in which case it would be Lower Silurian or even Laurentian. All the rocks of the Flinders Range lie above it, but as there are no fossils, nothing positive can be concluded as to their horizon. In describing the sandbed of the same locality the Chief Justice has fallen into a little error, which I am sure he will excuse me for pointing out. He says that he found a Succinea and a Pupa apparently of the same species as those figured by Lyell as coming from the Loess of the Rhine, viz., S. elongata and P. muscorum. Sir C. Lyell's work is not considered a very safe guide on matters palaeontological, and as it happens the species of Pupa in question is recognised by some authors as a Pupilla. It still lives in France in damp and shady places, and is about one-twelfth of an inch long. Of course I don't say that Mr. Hanson's species is not identical; but here is the diagnosis of Lamarck, and he can compare for himself:- "Testa minima .cylindracea obtusa loevi, corneo fuscescente, unfractibus convexis, suturis excacatis; apertura unidentata labro margine reflexo." (Vol. 6, part 2, p. 111.) The Succinea is European too, but the figure of Lyell is faulty. Both, however, are existing species, and have not been found out of Europe. Physa elongata, described by Say as an American species, is also mentioned by Menke as occurring in West Australia, but no European land-shell has ever been described as living in Australia, nor is it according to analogy to suppose that any ever will be. Therefore I think Mr. Hanson's identification doubtful. But the mistake I wish to point out is that Mr. Hanson regards the deposit as a marine one, and he speculates on the land at the mouth of Port Elliot being much larger to make the sea sufficiently tranquil for its growth. But the formation is, from the shells he describes, evidently a sub-aerial one, for none of the shellfish he names could live in the sea, nor even in water at all. In fact, I believe, he was dealing with drifted deposits collecting under the same conditions as that already referred to at Guichen Bay. These are the only remarks I shall offer on the paper of His Honor.    It may be thought that such errors as I have been careful to point out should be allowed to pass, as too captions a spirit of criticism tends to discourage observa­tions of the kind. But I apprehend that a Society like the Adelaide Philosophical Society, which proposes to record the progress of scientific discovery in South Australia, has a higher object than merely to encourage amateurs. its aim should be, and I am sure is, to study facts, and therefore I have felt it my duty, as my observations were in question, to put your members in possession of the facts of the case. Neither the society nor Mr. Hanson will be, I am sure, offended at this, especially when I remind them of Horace's words -
"Verum ubi plura intent in carmine, non ego paucis
  Offendar maculis, quas aut incuria fudit
  Aut humana parum cavit natura."

Note. - It is fair to state, with reference to Pupilla muscorum, that it has received many other names, and probably Pupa is the one most generally received. It was Leach, in 1820, who proposed the former name. (See Zool. Miscel., Part Conchol.) The list of synonymes for the genus is as follows:- Lauria, Gray, 1840; Eruca, Swainson, 1840; Sphyradium, Agassiz, 1837; Gastrodon, Lowe, 1852. P. muscorum is very closely allied to P. umbilicata, but is more cylindrical, and the last whorl smaller. Common in Britain on sand-dunes and sandy pastures, among roots of Psamma arenari, an allied plant to that which occurs in. Robe, extending along the sand in long runners, and sending suckers down at every joint, making the whole plant seem like one long root.

Succinea oblonga is a small species with three or four distinctly separated whorls, aperture oval and small in proportion to the size of the shell, being as long as the spine. It inhabits ditches near the coast and sand-dunes near the sea, covering its shell with a viscous secretion, and in winter burying itself in the sand. There are two inland stations for it - both in Ireland - but otherwise it is diffused throughout Europe, and occurs as a Pliocene fossil.

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PAPER BY HIS HONOR MR. CHIEF JUSTICE HANSON, READ MARCH 6, 1S66.

SUBJECT - 'THE GEOLOGY of THE SOUTH-EAST'

During a recent visit to the South-Eastern District of the colony I was struck with certain features of the country, and I thought that they might form the subject of a paper for this Society. On looking over my notes, however, for the purpose of pre­paring the present paper, I feel how meagre and imperfect my descriptions and theories must be. Still as a contribution towards the formation of correct views with regard to the past history of that part of the colony it may not be without its interest. The general formation of the district has been described with much accuracy by the Rev. J. E. Woods in his "Geological Observations of South Australia," and I have nothing to add to that description. But there are appearances to which he does not seem to have adverted, which may possibly require us to modify some of his con­clusions, and to some of these I shall briefly advert. But before doing this, I wish to take the opportunity of expressing my opinion of the breadth and soundness of the views put forth in that work, and of the general accuracy of the observations upon which they are based. If upon furthermore minute and detailed examination some of the conclusions of the rev. author should be found to require modification, or if it should appear that there are phenomena which he has overlooked or wrongly interpreted, this will in no degree detract from his merit as the first person who has attempted to comprise in one general view the whole geology of the district, and has succeeded in embracing the whole in an intelligible and consistent theory.

Mr. Woods considers that a limestone rock, answering to chalk, is the funda­mental rock of the district, and this he supposes to have been originally a coral reef. This is covered in places with a more modern deposit, which in the neighbourhood of Guichen Bay he thus describes:- "Round the coast (which, as before stated, princi­pally consists of coralline cliffs or hillocks), patches of a different kind of rock from the white chalky deposit are occasionally seen. At times it forms sea-cliffs of itself, and then it affords a good variety from the generally uniform white coast line, this being dark brown in colour, and more compact and rugged than the underlying strata. It is found more or less all round the coast of the colony of South Australia, and perhaps it extends all along parts of the Australian Bight. It is seen to most advantage where the coast is bold, and where it forms cliffs; and as a better idea can be gained of the nature of the formation from such localities; I shall confine myself to them for the present. The principal places, then, where the rock is observed to most advantage are Guichen Bay, a port on the South Australian coast, between the most southerly part of the colony and the Coorong; and an indentation on the coast between Cape Bridgewater and Cape Grant, a little to the west of Portland in the colony of Victoria. The whole eastern and northern sides of Guichen Bay are composed of low sandhills, scarcely 30 feet above the water level, but on the northern side a change takes place. The sand is replaced by rough craggy rocks, which, though not rising very high, are bold and abrupt, sometimes presenting a perpendicular face to the heavy surf which beats upon the coast. Seen at a distance one would imagine that these rocks were divided into larger strata, 14 or 16 feet thick; but on a closer inspection another kind of strata is discern­able. In addition to the great divisions which are so distinct, that one could almost imagine that they were huge slabs of rock laid upon one another, there is a cross stratification. This is a lamination which divides the beds into strata about two inches thick; but they are never horizontal like the real strata, are scarcely ever parallel, and never con­tinuous across the great divisions which divide one bed from another. Now, all these appearances, taken in connection with the mineral character now to be described, are clearly indicative of an ocean current. Any one conversant with the elements of geology will not require to be told why this conclusion from the facts above stated. It will be sufficient to say that the want of horizontality in the smaller strata is due to some disturbance in the water from which they were deposited, and as they bear in one particular direction, this must have been owing to a stream which deposited particles as it flowed along. The greater divisions are caused by an alteration in the current, which, before it would deposit any new matter, would carry away the lighter superficial particles, and wear down to a smooth surface all the inequalities left by the former stream. If there were any doubt about the theory it is quite removed by the nature of the rock. We know what kind of matter we should expect to see at the bottom of such a stream. Their course is generally slow, and therefore only small fragments of shells, grains of sand, and fine mud would be carried by them. A river will carry down mud from the banks and fragments of wood; but an ocean current which takes its rise in deep water can only have the detritus of the rocks and shells it has acted upon. The material of the rock now under consideration would appear at first to be a coarse-grained sandstone. Under the microscope, however, it is found to consist of small particles of shells, worn by attrition into thin scales; and small grains of a quartzose sand. It is freely acted upon by acids, and with the necessary reagents shows great quantities of lime, magnesia, and silica, with traces of sesquioxide of iron and sulphate of lime, but no phosphates or organic matter. There are no fossils excepting in a few places, which I shall specify.

From those facts, therefore, we may not only con­clude that the deposit was from an ocean current, but also that it was a considerable distance from any land, because coast drifts are generally rather rapid, being derived from large rivers or similar causes, while those far from land seldom exceed the rate of three miles an hour, and anything much quicker than this must infallibly have included larger particles of shells, and even whole ones. Guichen Bay is not so well provided with this rock as a small inlet at the south side of Cape Lannes - the promontory which helps to form the south-east side of the harbour. There the rocks are seen in bold section, for sometimes the cliffs are nearly 100 feet high. The little bay is very deep, so that the water washes the cliffs nearly all round. In some cases the action of the surf has nearly undermined them end caused them to fail, and the spray has eaten into its soft friable texture, giving parts a wild and jagged outline. These features and the singular cross stratification of the cliffs that have escaped the ravages of the ocean, the dark hue of the stone, the heaps of ruins scattered about like fallen castles, and the boiling of the heavy surf, which even in the calmest day breaks upon the rocks, make a sublime scene, which for wild beauty would be unequalled in Australia where it on a little larger scale. Even as it is, however, it reminds one of the bold coasts of the Highlands, and the little verdure which the mesembryanthemums give as they creep down the surface of the rocks, or hanging swaying in the wind, tends little to soften its desolate and savage aspect. There are, as I have stated, no fossils; but the summit of each cliff is topped by a stratum of compact limestone hori­zontally disposed, but lying uncomformably. This, I presume, is a relic of the last coast action before the deposits were upheaved to their present posi­tion; and from the fact that the stone lying in the same manner farther inland contains marine fossils of existing species, I have no doubt that it is of the same age as the very recent beds, to be spoken of hereafter, which exist all round the coast."

We have therefore upon this theory to suppose a time when the whole of the space at present occupied by the South-Eastern District, and in fact a very much larger space, formed an immense coral reef, which was gradually submerged and afterwards covered in places with such a deposit as is described in the extract which I have read. There are many questions suggested by this description which we have not probably the materials to solve; such, for instance, as the extent and position of the land along whose coasts the shells existed whose fragments form the largest portion of the upper deposit; the direction of the current which brought the materials; and others. If we might judge of the direction of the current from the present dip of the stratification, which now seems in the neighbourhood of Guichen Bay to dip towards the E.N.E., the current itself would seem to have flowed from the W.S.W., in which direc­tion there is at present no land for more than 1,000 miles. Possibly, however, this appearance is de­ceptive. It may arise from subsequent upheaval of the land, which may have been greater in some parts than in others, and thus have disturbed the original line of stratification. Mr. Woods suggests that the great body of land was to the northward. and considers that this would tend to account for the more tropical character of the fossil as com­pared with the existing testacea. And much weight is due to this suggestion. But it may, I conceive, be a question whether the existence of a tract of land to the southward, not extending too far, and with no mountains rising above the summer snow line, might not equally contribute to the production of this result by shutting out the cold southern currents, and by breaking the force of the southerly winds. It might produce a difference in the testacea somewhat similar to that which we find in vegetation between sheltered and exposed situations, and between a northern and a southern aspect. I apprehend, for instance, that the climate of the northern coast of Africa on the Mediterranean is warmer and more equable than it would be if no land interposed between it and the Arctic Ocean. These are, however, points which we can only indicate as open for investigation, and which may ultimately receive a probable solution. In the neighbourhood of Guichen Bay, to which I must in a great degree confine my present observations - for my means of observation were limited by the very narrow range within which my walks were confined - in that immediate neighbourhood there are other appearances which seem to indicate changes, subsequent in point of time and possibly even of a different order to those which have

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been just referred to it. In the southern corner of Guichen Bay, near the jetty, there is what may be almost termed a low cliff of dark sand, very diffe­rent from the ordinary sea sand, and having appa­rently a different origin, interstratified by layers of shells, principally a large univalve - a Trochus I believe - and rising for about 10 feet from the level of the present beach. The dark colour of this sand is clearly not attributable to vegetable deposits, for the regular occurrence of sea shells in lines at various heights shows that it was deposited in a sea in which these shells could live. And there is not, so far as I am aware, any part of the coast where a similar formation is now in progress. Whatever, therefore, the cause may have been, it was temporary and partial. I confess to me it suggested a volcanic origin, and I was led to conjec­ture a time when there was some active volcano in the neighbourhood which at intervals poured skewers of ashes into a sheltered arm of the sea.* The sand itself is very incoherent, and probably had originally a very much greater depth than it at present possesses; for the surface is strewn with similar shells, which apparently - I might perhaps say obviously - have been derived from the waste of this sand, which is blown off by the wind and washed away by the rain. The sur­face is, however, now partially protected by the grass and rushes which grow upon it, and the face to the sea is nearly perpendicular. Immediately behind Robe, nearly due west, is the bay referred to by the Rev. J. E. Woods in the extract which I have already read. The cliffs there rise from 60 to 100 feet, and upon the summit of these cliffs, above the limestone crust which covers the crag formation, there are patches of this dark sand, with its interstratified shells, though not more than two or three feet in height, and only remaining where they are protected by the growth of shrubs or rushes. It would seem, however, that the whole surface had been at one time covered with it, and it is quite certain that it was originally more extensive than at present, for the characteristic shells are widely strewn along the summit of the cliff, and fragments of them are found all over the neighbourhood. This, however, necessarily sug­gests a period after the formation of the crag deposit, and of the limestone crust by which it is capped, when the whole district formed the shallow bed of a sea of nearly the same depth, and when the portion now occupied by the cliffs to the east was at the same general level as that on the shores of Guichen Bay itself; and hence it suggests the existence of a cause of upheaval which operated unequally, and which, to judge from its effects, must have been situated somewhere to the west of the present coast-line. At the time of the upheaval, however, the whole of the district in which any of these patches of dark sand remain must have been protected from the action of the waves of the open sea, and the upheaval must have been gradual and unaccompanied by any convulsions, at least until the sand was raised above the reach of the waves, since it must otherwise have been entirely washed away. And the same con­clusion is derived from the character of the crag rock, large portions of which are so loose and incoherent that they could have offered no resistance to the action of the waves even for a very short period. In this particular district, consequently, we have to suppose that, subsequently to the period when the crag rock was raised near the surface, some cause existed which is no longer operative, and which occasioned the deposit of strata of dark-coloured sand to a considerable thickness and during a long lapse of years, and then a process of upheaval which raised both the crag and the overlying sand above the level of the waves, and which operated

   * It was suggested by Mr. Smeaton, in the discussion which followed the reading of this paper, that the dark colour of the sand in question was owing to its having been intermingled with large quantities of seaweed; and he stated that he had taken portions of the sand to spread on his walks, and that in a short time the dark colour was washed out of it. This suggestion is more simple than that which occurred to myself on examining the place, and is perhaps the more probable. Its adoption would not, however, necessarily require any modification of the other conclusions I have drawn.

unequally, and apparently exerted its greatest force to the west. The same reasoning would show that there must have been a very considerable waste to the west and south. For at the present time the coast there is exposed to the full force of the South Pacific, and the sand which is blown up and which now forms sand dunes along the greater part of the coast, though principally composed of fragments of shells, does not contain any portion sufficiently uninjured to be capable of recognition. All are broken by the force of the waves into minute fragments. The shells, however, which are found in the patches of dark sand to which I have referred on the summit of the cliffs at the back of Robe are frequently almost uninjured, and some retain their forms altogether unworn, and as sharp and well-defined as though they had been only just taken from the surface of the rock. It would seem, therefore, that at the time of their deposit some land must have existed where the open sea now spreads to the south and west, which sheltered the place of their growth. This may have been washed away by the force of the waves; but it is also possible, and perhaps upon the whole more probable, that the elevation of the sea bottom in parts may have been accompanied by subsidence in others, and that the change in the physical configuration of the land is attributable rather to such a subsidence than to the mere action of the waves. I have said that where this dark sand is found on the summit of the cliff to the west of Robe, it rests upon the stratum or rather layer of compact limestone, which Mr. Woods has described as capping the crag. Whenever I was able to examine this superficial covering it appeared to owe its greater hardness to the same cause that produced the concretions to which I shall subsequently advert, viz. the action of water charged with some hardening ingredients upon the surface of the less compact calcareous sandstone below. Generally the rock underneath is penetrated by these root-like concretions, and is tolerably compact; but there is one place in the bay to which I have referred, where the cliff is highest, in which a considerable portion of rock of a very loose texture intervenes between the two formations - the layer of com­pact limestone at the top and the hard rock below. 

This softer part is at present beyond the reach of the waves; but it has weathered considerably, and instead of standing perpendicularly, or even over­hanging its base, as is the case ^-with most of the cliff's, it recedes at an angle of about 60%. It is apparently rudely stratified, and the divisions of the strata appear to run horizontally, following the curve of the bay, though, so far as I could judge, they dip inwards towards the north-east, corresponding in this to the, rock beneath. Below the more compact stratified rock which underlies the formation list described there is in many parts another rock of similar composition and hardness, in larger masses, and presenting no sign of stratification that I was able to observe. This last, which is the lowest rock visible, appears to be of equal hardness throughout, and to have been wasted equally. In the bay referred to, con­sequently, there are in places four distinguishable fomations - the lowest without stratification, suc­ceeded by one which is stratified, and which is traversed throughout its whole substance by root­like concretions. Above this, again, in one part at least, is another of similar mineral composition to the two others, being, like both of them, composed almost entirely of waterworn fragments of shells and, like the second, stratified, but very far less coherent, and with none of the concretions; and above this the compact limestone, which is only in a thin layer, and which appears to have been hardened by the superficial action of water. And above these is the dark sand which I have described, with its characteristic shells. At the north of Guichen Bay the Baudin Rocks are formed of the second formation I have described - the stratified, with concretions; but I was not able to visit the outlying rocks, and on the coast they are too low to enable me to observe anything more than their general character. On the beach there I found many flint-stones, which belong to a for­mation lower than any of those which I have de­scribed, and have presumably been washed out of it. In traversing the South-Eastern District it is impossible not to be struck with the evidences of elevation of the land, which are almost everywhere visible. Throughout large tracts, wherever a tree is blown down, the roots are found to have brought up numerous sea shells. ln many places sea shells ­are found on the surface of the soil, scarcely covered with earth, and showing by their sharpness of outline and uninjured condition that they must have died upon or close to the spot where they are found. Lines of low rocks are seen at intervals; stretching, I am informed, in many instaaces for miles, which are obviously the remains of old sea beaches. And these appearances give weight to the various indications from which it is judged that the coast - and with the coast the whole of the interior - is now in process of elevation. But it is very doubtful whether there are any reliable signs of this process of upheaval having been interrupted by periods of subsidence. It is true that the first impression produced by the appearance of the cliffs to the west of Guichen Bay, in the bay to which I have previously referred, and in the rocks in Guichen Bay itself, is that there must have been very marked subsidence since the first deposit or upheaval of these cliffs. The substance of the rock is in most parts penetrated by root-like concretions, which suggest in the first instance to every observer that they are really petrified roots; and every here and there, on the summit, there are projecting pieces of limestone, which resemble the stems of the low bushes that grow around. When I first saw these appearances I was impressed with a belief that they showed a period of subsidence after a former period of elevation which had allowed the growth of bushes and other plants that sent their roots far down into the subjacent sandy rock or sand; and it must be confessed that such a conclusion is not altogether without probable support. The substance of the rock is composed of materials which are scarcely distinguishable from those of the sand dunes which stretch away to the southward, and the depth to which roots now penetrate the loose sand of these coast dunes is equal, I believe, to any depth to which the root-like concretions have penetrated. I found some roots of a species of flag which grows just inside the summit of the dunes fully 14 feet in length, and then they did not terminate, though I was unable to trace them further without breaking them; and the term and appearances of many of the concretions are preciselyy similar to those of fragments of the stems and roots which may be seen about. But there are, on the other hand, very ­great difficulties in the way of any such a theory. No traces of solidification are found in any of these dunes, and it is only in them, so far as I am aware, that the roots penetrate, or, in fact, could penetrate, to a depth at all corresponding to that which is reached by the concretions, and the sands of which these dunes are composed are so loose and shifting that it is difficult to conceive how they could ever be solidified while above water, or how, if they had been formed under the air and afterwards submerged before being solidified, they could have escaped being entirely swept away during the process. And in addition to this ground for supposing that the concretions do not represent roots, a further reason is furnished by the circumstance that they are found principally, if not exclusively, in those parts where the rock is stratified, while the dunes, which are entirely subaerial formations, show no approach to stratification. There is, as I have already described, in some parts an amorphous rock under the stratified portion, but no concre­tions are seen to penetrate this. Although, therefore, I do not regard the question as definitively settled - for we do not know whether changes may not even now be taking place at the base of these sand dunes under the influence of pressure and moisture, which may make the lower parts more solid - I think the preponderance of evidence tends to show that these concretions are due to the infiltration of water charged with some hardening ingredients, and do not mark the course of roots. And this opinion has been confirmed by the circumstance that in the tramway cutting near Port Elliot I found in the super-incumbent limestone very similar concre­tions which it was difficult to refer to roots; and on the sand in the bay of Port Elliot, some short distance above high water mark, I found project­ing stems, if I may use the expression, of limestone, undistinguishable in external appearance from those to which I have referred as being found

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on the summit of the cliffs to the west of Guichen Bay, and in a place where, so far as I could judge, there was no reason to suppose that any shrub had ever grown. The existence of these concre­tions, consequently, does not give any support to the assumption that the rock was above the sea at the time when they were formed, and consequently affords us proof of subsidence. There is, however, a cave near Mount Burr, known as the Bone Cave, which does appear to me to furnish evidence fronting in that direction, and which, though not conclusive, is most consistent with the existence of a period of subsidence after pre­vious elevation. And as the matter is of some interest as affecting the geological history of the district, I will briefly state the reasons for such an inference. The Bone Cave is situate in a low line of inland cliff fronting to the west or south-west. ln front of a portion of the cliff there is a small piece of swampy ground into which the water of the immediately adjacent land drains; and one entrance of the cave - that by means of which the interior is most easily reached, if it can at all he reached by the other - is just in front of the swamp and nearly level with it, so that it would appear that the water must drain into the cave in rainy seasons. The front of the cliff and its summit bear, everywhere, marks of the action of the waves, and the ground in front is strewn with frag­ments of rock which have fallen from the cliff, in the same manner as the exposed shore near Guichen Bay is at present strewn with similar blocks. In fact, no one, I should assume, looking at the spot would doubt that the rock was formed into its present shape by the action of the sea.

There is a frag­ment in front of that opening to the cave in which the bone deposit is found which has a blowhole through it, and which has obviously fallen into its present position since the formation of the blowhole, as the direction of the hole as it now lies is hori­zontal instead of perpendicular. The bone-earth is found only on the roof of the cave, some eight or ten feet above the level of the swamp, though not more than four or five feet above the earth immediately in front; for in that spot there has been a deposit of earth washed down from above through a slight depression in the rock just to the right of the entrance under the bone-earth. The depth of the cavern originally was in all probability somewhat below the present level of the swamp, so that there was probably a depth of 10 or 12 feet between the lower surface of the bone-earth and the bottom of the cave at its mouth before the earth was washed into it. The bone-earth forms a kind of breccia of reddish earth and bones, cemented by lime to the roof. It would seem impossible that the bones and earth could have been cemented to the roof by any pro­cess, unless the lower part of the cave was in the first instance filled up. There must have been a support to the upper deposit which now remains - or, in other words, the breccia must have first formed upon the floor of the cavern, and then have been raised by further accumulations up to the roof; and it would seem equally impossible that this could have been done, that is, that the whole cave could have been filled up, while it was exposed to the waves. The general way in which such caves are filled is by the sweeping of earth and bones into them, which are cemented by lime into a compact mass at the bot­tom; and the mass thus formed is gradually raised by new additions until it reaches the roof. and first checks and then ultimately diverts the course of the waters which originally flowed into it. But in order to effect this it is necessary that the mouth or some part of the cave should be obstructed so as to ensure the deposit of the various articles which are swept down; since otherwise the same force which brought them into the cavern would sweep them through. The cave must be filled from the bottom, and either the outlet of the waters must he of such a nature as to impede the passage of solid articles swept down, or the form of the cavern must be such its to cause their deposit in some hollow or depression before they reached the mouth. At the time, consequently, when this deposit was formed the whole of the part at pre­sent occupied by the breccia, and so much further as the breccia extended, must have been protected from the action of the sea, either by being raised above it, or by the cliff having through the whole period during which the bone-earth was accumulating extended so far beyond the place of the deposit as to protect it from the action of the waves. It is impossible that the mouth of the cave could have been open as it now is. The breccia must have been formed in a place to which the waves had no access, and then, either by a change in the level of the land or by the gradual encroach­ment of the sea, the waters of the sea obtained access to it and re-excavated it, sweeping out the lower portion, and breaking down some part of the roof of the cave with the bone-breccia still adhering to it. At the rate at which the sea is gaining upon the land at the present time, and taking into con­sideration the extreme hardness of the rock, this would have been a process requiring a long lapse of years, during which we must suppose that the process of upheaval which had previously brought the rocks in which the cave is situate above the level of the water, and which is now continuing, was interrupted. I need hardly say that there is no more difficulty in supposing a period of partial subsidence being interposed between two periods of upheaval than there is in supposing a period of absolute rest to be so interposed; and though I express the opinion with much diffidence, I confess that the impression made upon me by such an examination of the place as I could give was that there must have been such period of depression. Another circumstance which appeared to ins to favour such a view was the very great alteration which must have taken place in the natural features of the country and in its drainage since the Bone Cave was filled. In order to have reached the summit of the cave the bones must have been brought in by running water, and there is no present drainage in the neighbourhood, so far as I could perceive, which would have done this. They could not have dropped in from above, for they are cemented on to the solid rock forming the roof of the cave; and as, on the assumption that there has been no subsidence of the land subsequent to their deposit, the natural features of the country could, so far as appears, only have been altered by atmospheric agencies, I confess that I cannot conceive of any change so complete having been affected by these causes. It appears, therefore, to me that there must have been a period of upheaval during which this cave was formed (or rather a cave, for it is possible that the existing cave is much deeper than the original; then that the bone-breccia was formed slowly, as we know that all such deposits necessarily are formed; then a period of subsidence and re-elevation, during which the cave was re-excavated and probably enlarged, and the natural features of the country altered; and then the superficial changes by which the swamp has been formed and the entrance of the cave partially filled up by earth swept in from above. Since the date of our last meeting, for which the previous part of this paper was prepared, and at which but for my mistaking the hour of meet­ing it would have been read, I have paid a short visit to Port Elliot, and I venture to add a few notes on the geological features of that dis­trict, to eke out the scanty observations which I have thus put together with regard to the geology of the South-East. They are necessarily very imperfect, for my stay was short, and my opportunities of investigation very limited. From the eastern head of Port Elliot to Rosetta Head there are masses of granite at intervals along the coast, forming the eastern and western heads of Port Elliot and the small island which partially protects the anchorage, then, after an interval, appearing at Granite Island, and finally rising to a considerable elevation at Rosetta Head, At Middleton, to the east of Port Elliot, what appears to be the fundamental rock of the district, a sort of schist, in some places highly micaceous, and in others without any appearance of mica, is seen cropping up. The strata appear to dip towards the north-east or north, at an angle of from 70º to 80º.

At Port Elliott I did not see any indications of this rock; but at Granite Island there were numerous fragments embedded in the granite; and in some cases, owing to its greater power of resistance to the action of the waves or of the atmosphere, whichever was the denuding agent, it stood out several inches front the surface of the granite rock. At Rosetta Head, on the rock which joins the Bluff to the main land, the schist is seen cropping out at the same angle, and with the same dip, as far as I was able to determine in the absence of instru­ments, as at Middleton; and in a small bay on the western side of this rock it is seen exposed, extending for some short distance into the sea, its jagged and broken outline forming a striking contrast with the rounded forms of the granite. At Middleton the schist is of a brownish colour, and is traversed in parts by thin veins of an intrusive rock, of which, unfortunately, I was unable to obtain specimens, at right angles to the apparent stratification. And in the bay to the west of Rosetta Head, the schist, which is of a dark slate colour, is traversed in places by veins of quartz not more than from one-eighth to one-sixth inch in thickness. The line of the stratification of the schist is here nearly east and west, and its dip north, at an angle of about 80º; the direction of the quartz veins is from about E.N.E. to W.S.W., and they appear to be quite vertical. In other places the strata of the schist are contorted by the intrusion of blocks of quartz, as though these latter had been thrown down in the bed of the sea while the strata of the schist were in process of deposition and soft. The lines of stratification curve round the quartz on both sides. By the side of the schist in this bay there are numerous boulders of granite, some containing large fragments of schist apparently unaltered. I had no opportunity of seeing how far the schist extends to the westward beyond Rosetta Head, but I believe there are no traces of it to the eastward beyond Middleton. A similar formation, however, exists in the hills behind Port Elliot, and it is quarried there and brought into the town for building purposes. I have said that the schist is seen on the neck at Rosetta Head cropping out. It is there at a height of, I should suppose, more than 100 feet from the level of the sea. On the neck rounded blocks of granite are scattered about, but in small numbers and of small size. As you ascend the Bluff you see blocks of granite, many of them enclosing unaltered fragments of the schist. And higher still, on to the very summit of the Bluff. you see the granite in large masses worn into singular shapes, but all more or less rounded. I am inclined to refer the shape of these blocks principally, if not entirely, to the action of the waves, for nearly all of them are now covered with a species of lichen, showing that the atmosphere can have very little present effect upon them. Descending the Bluff on the western side, pieces of schist are seen with the stratification less distinctly marked, and in some places it is seen cropping up in situ, obviously much waterworn. The granite on this side of the Bluff is much worn, and in one place in particular, where it seems as though an enormous fragment had fallen, and was supported by other fragments, the under surface of the fallen rock is hollowed out, so as to form a kind of cave. As the portion so hollowed out is protected from rain, and in a great degree also from the spray, I am inclined to be­lieve that it must have been hollowed out by the action of the waves before it was raised to its present position. It is, however, quite obvious that the greater part of the wasting must have been due to that cause, and the same cause is still wearing away the granite at the level of the sea and as far as the force of the waves reaches, though very slowly. In a mass of granite, which has been worn nearly to a level, some 20 or 40 feet below where I stood, and to which I was not able to descend, there was a large frag­ment of schist of an irregular form, about four feet in length by about 18 inches broad, embedded, and some smaller fragments near it. It is obvious from these appearances that the formation of the granite was subsequent to the deposit and solidi­fication of the schist, and that the whole of the granite was at first underwater. The very highest portions of the granite everywhere show unmis­takable signs of the action of the sea. There has then been an upheaval, which has raised both formations, and which apparently exerted its greatest force at Rosetta Head. The upheaval must have occurred at a very recent geological epoch, since a limestone crust, similar to that which is so extensively found in South Aus­tralia. is found also on the summit of Granite Island in parts covering the granite. It does not, however, so far as I could discover, contain any fossils. The granite is as a general rule very coarse, probably from the circumstance

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that it did not solidify under great pressure, for it does not seem that there has been any great superficial denudation. On the east of Port Elliot, however, in the coarse gray granite, there is a block of very fine-grained reddish granite embedded, harder or more compact, and therefore wasting more slowly, protruding from 9 to 12 inches from the surface. Here the granite is traversed by veins of quartz from 3/4 to 1 1/2 inches in width. They may be traced for many yards, some­times as far as the granite itself can be traced, till it is covered with the sand - running straight for a considerable distance, and sometimes throughout, but in some places contorted. In a cutting of the tramway between Port Elliot and Victor Harbour there is a bed of dark-coloured earth, in which shells of a species of Arca are found, with oyster-shells and some others. No oysters are, I believe, found anywhere along the coast at the present time, and the Arca do not, I understand, attain nearly an equal size. I was indebted to the kindness of Mr. James, the Manager of the Tramway, for some specimens of these shells. On the beach at Port Elliot, some distance from high-water mark, there is a small mound of dark earth, about 5 feet high and 3 or 4 feet square, with nearly perpendicular sides. It is quite inco­herent, and in a constant course of wasting by the mere action of the wind; and the wonder is how any part of it could have remained. In examining it I found some shells of a species of Succinea of a Pupa - I think Pupa Muscarum - and of a Helix. It is singular that shells of those three families, and two of them apparently of the same species - the Succinea and Pupa - should be figured by Lyell in his "Elements of Geology" as the characteristic fossils of the Loess of the Rhine. Higher up there are some other patches of the same earth with similar shells, and on the sand of the beach between the two spots I picked up many shells of the same species of helix,apparently blown there from the land. I suppose, therefore, that it is not uncom­mon in the neighbourhood, though as I left the next morning after finding these I had no oppor­tunities of making enquiries. There was another shell of a species I am not able to determine. I should mention that in the same sand I found one or two fragments, and a whole shell of a species common on the coast at the present time. This formation points not only to a continuance of the process of upheaval, but also to a change in the character of the coast-line since these shells were deposited. It is obvious that no similar deposit could take place at the present time. The sea sand surrounds the deposit on all sides, and in a short time comparatively the whole will he blown away or covered with the advancing sand. In order to the formation of such a deposit there must have been some shelter, and that probably points ­to a time when the island in front of the harbour was much larger than it is at present, and sheltered the entire bay, and possibly also, to a time when the drainage of the country was  different. It has been suggested to me that it may even point to a time when the Murray flowed along the base of the hills and entered the sea by Port Elliot; but this is a suggestion of which I have no means of estimating the probability or even possibility. So far as I could conjecture - for any view I might express on the subject would be only a conjecture - I should deem this improbable; but I could imagine a time when the waters of the Murray spread more widely, and when the marshy margin of the lake might even have reached as far as this.