THE LOST ANTARCTIC CONTINENT.

Otago Daily Times, Issue 14084, 12 December 1907, Page 2

THE LOST ANTARCTIC CONTINENT.

(Bv B. M. Laing, M.A., B.Sc.)

n r °'l 3 , lll0 i t!cep ' whcro " tn ' tllf lr <*. Ocaith, what changes lias thou seen! there where the long ftreet roars, hath been The stillness of the Ccivtral Sea.

Islands are, divided into two groups by geologists and biologists. Those islands which at some period of their existence f 0 ™" 1 P®rt of a ]ar t e land mass are termed continental.' Great Britain is an excellent example of this class. In quite recent times, geologically speaking, Th-Tff , 7 , n of tLe C ° n,inent of Europe J lie cliffs of Dover are reproduced on tho ire, side by the corresponding cliffs north of Dieppe. The lowlands of Hoiland are manifestly part of the lowlands round the Vl asli. The plants and animals or Great Britain aro with onlv some insigniiicant exceptions the same as those of the Continent of Europe. Geologically botamcally _ and zoologically, therefore,' ea t Britain is part of tho great land mass of Eurasia. Indeed, from this standpoint, it is only an unimportant incident that England happens to bo separated from the mainland by the shallow Straits of Dover. On the other hand, take such an insular group as that of Cape Verde or the Galapagos. Such islands are termed oceanic. They are usually formed either by the action of volcanos or by the coral poly)). They rarely conUin masses of the older rocks such as granite gneiss, or syenite; and fossiliforous strata are usually wanting in them. Their plant and animal lifo is sparse, and has generally come to them from oversea, conveyed by tho wind, by birds, or by ocean currents. Jlanv of the plants and animals of Continental islands, 011 the contrary, are such as could not cross even a narrow Strait, They must have reached their present habitats by way of tho land. Now, the study of tho origin of our land surfaces has led us to many strange conclusions as to their past history. It is obvious to the most casual observer that land-forms are continually changing, in one place rising from the sea and in another sinking into it. The amount nf these eiiangcs has been much discussed, and it is generally supposed that great ocean basins such as the Atlantic have throughout- the Tertiary Era occupied their present areas. There may indeed nELYc I)6cii ti rise or foil of tho l.uid surface equal to about one-third of the present Continental areas. This generalisation may bo regarded as fairly well established for tho northern hemisphere: but its application to southern eeas is by no means clear. It is quite possible that even vaster changes have taken place in them even in comparatively recent times than in tho relatively moro stable northern continents. At any rato there are many phenomena of plant distribution in southern zones that seem to indicate a closer connection in the past between lands now a hemisphere apart. Round the globe between latitudes 50 and 60 degrees lie groups of islands now widely sundered that show affinities of the most striking character. These can scarcely be explained, except by the theorv that these islandis at one time belonged to some continental land mass. The geological structure of tho Auckland and Campbell Islands is shown by tho recent investigations of Dr Marshall and Mr Speight to be. as far as might be expeclcd, in accord with such a theory.

Let lis consider shortly as an example the case of the Auckland Islands. They may be compared in their general appearance io Hanks Peninsula, but with a difference. Imagine a- peninsula placed out- in the open ocean in a region of furious and continuous westerly winds. It is clear that under such circumstances the weather side of the island would be quickly eaten away owing lo marine erosion. This, if continued throughout many geological' ages, would in course of time destroy the island altogether. As a matter of fact, there is clear evidence thatt a considerable portion of tho Auckland Wand lias thus been washed away, for its chief watershed is not in the centre of the island, as might be anticipated, but on tho edec of tho great western cliffs. Idnst of tho streams of the island flow into the east coast and rise within a few yards of tiie west coast. If we were to. suppose the western half of Bank's Peninsula to be shorn off, the remainder would form a fair model of Auckland Island. Akaroa harbour would correspond to Carnley harbour, and Lyttelto'n to Port Ross." Evidently then, these islands wcro at one time much larger than their present size. But we have a further geological proof of greater land extension in the signs of glaciation found upon them by tho geologists of the fouthorn expedition. We arc still largely ill the dark as to the causes of the extensive gkciatinn thai, prevailed at. various times in past, geologic ages; hut there can be 110 doubt- that 0110 of them was tho former greater extension of the land masses _ and tho greater altitude of the mountain ranges. If, for example, the sea bottom, round the Auckland Islands were lo bo Taisedl a thousand fathoms, there would be mountains upon the land 8000 ft high, and these would doubtless contain huge glaciers in thoir valleys. Now, unfortunately, very few soundings llavo been taken between the Auckland Islands and New Zealand, but. such as tliey are they seem to show that between these two places the sea is nowhere deeper than 1000 fathoms: or. in other w»rds. that New Zealand and the Auckland Islands lie uuon what geologists term a continental shelf. It is no" extravagant, supposition to believe that at one time this shelf m:tv have been dry land. The presence of fossil shells at much greater altitudes than 6000 ft. in mountain ranges shows that such elevations liavo not been uncommon in tho past, Tliore is nothing, therefore, in tho present surroundings of the Auckland Islands lo disprove the hypothesis that tliey have at one limo formed part of a greater land mass. Indeed, tho presence of granite rocks in Carnley harbour, and of old sedimentary rocks on Pi6a]iDointment Island, tends distinctly to show that these islands belong to the Continental type; but such evidence as this, though suggestive, is bv no means conclusive.

Let us shortly examine the question now from another point of view—the biological, or rather the botanical; for the zoological point of view has, or will be. dealt with in another articlo of this series, and for this purpose let us turn to another sub-Antarctic island, which, though under the jurisdiction of Tasmania, is really geaffraphicallv connected with New Zealand. This is Macquarie Island. Only twenty-seven species of flowering plants are known from it. Nine of these are found in Fueeia, and six occur in Kerguelenland. These coincidences are seen to be the more remarkable when the distribution of individual snecies is considered. There is a little buttercup which is found only on Macquarie Island and Kerguelen Lind, though a closelv allied foiTu is found in Fnerria, Falkland Islands, and Marion Island. Another very distinct and remarkable nlant (Azorella selasw) is found onJy on Karauaric Island, Kergue-

len Land, the Crozets, Marion, and Heard Islands and; iu Fucgia a little seaside plant (Cracrula morehata) is found throughout the sub-Antarctic islands and in New Zealand. A closo analysis of the florulas of tbo sub-Antarctic islands leads to the inevitable conclusion that they have had a common origin. Now there are three causes worthy of consideration, to which these relationships may ho due. The plants may have been distributed by the westerly winds whirh blow round the earth in the "roaring forties" or the "roaring fifties," as they should moro properly be termed, or fliey may have been carried from land to land by seabirdfl, or they may have been derived from the same common land surface. It is, however, impossible in an article such as this to consider nil the "pros and cons" of tho case. Suffice it to say that there are many little pieces of evidence which suggest that tho third explanation is probably the true one. It cannot, however, be denied that it. is quite possible that some species of plants may have been carried from island to island by such birds as the albatross. Thus tho well-known piri-piri (bidi-bid of tho colonists) grows not only throughout New Zealand, but also in the Auckland, Camphell, Antipodes, and Macquarie Islands, and also in Australia, Tasmania, and Tristan d'Acnnha. It may he doubted' wliethor it is tho same species which is found in all of these places, but at anyrale, the forms are so closely allied that they may for our present purposes be considered as one. Now these burrs have been observed to adhere to the feathers of the albatross, and it is quite possible that this bird may have been tho agent in distributing it throughout these lands, but the probability of this is not so great as might at first sight appear. Let us grant that some seeds of the piri-piri are taken from one island fo another where tho plant does not grow. Before it can maintain itself in its new homo it must fight its way amongst tho previous occupants of the land. It must succeed 111 the strugglo for existence, when other plants fail. It must be so plastic as to be able to adapt itself to new conditions, and, having got- a foothold, it must be ablo to propagate itself successfully ill its new environment. , Nevertheless, it is clear that very few plants thus suddenly introduced into fresh surroundings call hope to compete successfully with those already there, and increase in numbers. It is true that in New Zealand we have seen many introduced weeds taking possession of the land almost to tho exclusion of everything else; but this is only after tho land has been cultivated, or the bush upon it has been foiled, or man lias in somo way interfered with the natural equilibrium of tho plant lifo of the district. Had these plants been introduced in small numbers into a situation where tho natural vegetation liad been left undisturbed by miui and by animals introduced by, him, their chance of survival would have been 6mall. In many mountain gorges of tho South Island, where sheep have never penetrated, scarcely any introduced plants aro to be seen. From these and other considerations there is a tendency at the present time to consider the changes brought about in plant distribution by 'tho action of the wind and of birds to bo fewer than was at one timo supposed, Nevertheless, given unlimited time, it is very difficult to say how far such changes may be duo to other agencies than a continental connection. It is, indeed, impossible to ascertain definitely how individual species have passed from land to land. But here modern plant geography comes in and gives us 6ome assistance. Forexample, tho botanist in Stewart Island everywhere meets with forests consisting ehicfly of tho following trees:—Tho southern rata, the long-leaved grass-tree, the simple-leaved panax, and the kamaki (Weill,'umia). On going to the Auckland Islands bo is brought face to fnco with the same plant, association in the forests, the only ditferenco being that the kamaki is wanting. It may bo possible to imagine that individual species may have passed from Stewart Island to the Snares otherwise than bv a land connection; but it is certainly difficult to imagino that a whole plant association should have journeyed south in any oilier way than by a land bridge. Here, indeed, we have strong evidence that in the past a greater New Zealand existed. Similarly, the "birch" forests of New Zealand, bear a _ very striking resemblance to certain "birch" forests in Patagonia. Evidence such as this cannot be disregardel: and so there has grown up, in the minds of great writers, such as Hooker and Wallace tho conception of a lost Antarctic continent, This, it .is supposed, stretched northward from the Antarctic circle, and included New Zealand and Tasmania, with all tlio sub-Antarctic islands (Kerguelen Laud, Tristan d'Acnnha, Fuegin, Fall;lands, Auckland Islands, Campbell Island, etc.). and at one time was connected with South America, and possibly also with South Africa. The age during which this extension occurred cannot at present bo determined: and, indeed, the chief evidence regarding this point is to bo obtained from animal rather than from plant life, consequently no attempt will be made to assign a date here.

A great- (leal of work lias been done during the last- five years by t-lio German vessel Vladivia, and bv the various Antarctic expeditions in the investigation of nlant and animal, life in these southern islands; and when the results obtained by those cxnoditions are collated with tlioso of the Hinemoa expedition it is probable that, our knowledge of the lost Antarctic continent will be put on a Bounder and more determinate basis,