602 



NA TURE 



[October i6, 1890 



■been the result ? Has the viscosity of the ice been modified by 

 the intercalation of beds of rigid lava and of hard-set ash ? Does 

 the growing mass tend to pile up or to settle down and spread 

 out ? Is the ice wasted by evaporation, or does the ash-layer 

 preserve it against this mode of dissipation ? These interesting 

 questions can be studied round the South Pole, and perhaps 

 nowhere else so well. 



Another question of interest, as bearing upon the location of 

 the great Antarctic continent, which it is now certain existed in 

 the Secondary period of geologists, is the nature of the rocks 

 upon which the lowest of these lava-beds rest. If they can be 

 discovered, and if they then be found to be sedimentary rocks 

 such as slates and sandstones, or plutonic rocks such as granite, 

 they will at once afford us some data to go upon, for the surface 

 exposure of granite signifies that the locality has been part of a 

 continental land sufficiently long for the weathering and removal 

 of the many thousands of feet of sedimentary rocks which of 

 necessity overlie crystalline rocks during their genesis ; whilst 

 the presence of sedimentary rocks implies the sometime proximity 

 of a continent from the surfaces of which alone Jthese sediments, 

 as rain-wash, could have been derived. 



As ancient slate rocks have already been discovered in the 

 ice-clad South Georgias, and as the dragnets of the Erebus and 

 the Challenger have brought up from the beds of these icy seas 

 fragments of sandstones, slates, and granite, as well as the 

 typical blue mud which invariably fringes continental land, 

 there is every reason to expect that such strata will be found. 



Wherever the state of the snow will permit, the polar moun- 

 tains should be searched for basaltic dykes, in the hope that 

 masses of specular iron and nickel might be found, similar to 

 those discovered by Nordenskiold, at Ovifak, in North Green- 

 land. The interest taken in these metallic masses arises 

 from the fact that they alone, of all the rocks of the 

 earth, resemble tho«e masses of extra-terrestrial origin which 

 we know as meteorites. Such bodies of unoxidized metal are 

 unknown elsewhere in the mass, and why they are peculiar to 

 the Arctic it is hard to say. Should similar masses be found 

 within the Antarctic, a fresh stimulus would be given to specu- 

 lation. Geologists would have to consider whether the oxidized 

 strata of the earth's crust thin out at the poles ; whether in such 

 a case the thinning is due to severe local erosion, or to the pro- 

 tection against oxygen afforded to the surface of the polar 

 regions by their ice-caps, or to what other cause. Such discoveries 

 would add something to our knowledge of the materials of the 

 interior of our globe and their relation to those of meteorites. 



Still looking for fresh knowledge in the same direction, a 

 series of pendulum observations should be taken at points as 

 near as possible to the Pole. Within the Arctic circle the pen- 

 dulum makes about 240 more vibrations per day than it does at 

 the equator. The vibrations increase in number there because 

 the force of gravity at the earth's surface is more intense in that 

 area, and this again is believed to be due to the oblateness of 

 that part of the earth's figure, but it might be caused by the 

 bodily approach to the surface at the poles of the masses of 

 dense ultra-basic rocks just referred to. Thus, pendulum ex- 

 periments may reveal to us the earth's figure, and a series of 

 such observations, recorded from such a vast and untried area, 

 must yield important data for the physicist to work up. We 

 should probably learn from such investigations whether the 

 earth's figure is as much flattened at the Antarctic as it is known 

 to he at the Arctic. 



We now know that in the past the North Polar regions have 

 enjoyed a temperate climate more than once. Abundant seams 

 of Palaeozoic coal, large deposits of fossiliferous Jurassic rocks, 

 and extensive Eocene beds, containing the remains of evergreen 

 and deciduous trees and flowering plants, occur far within the 

 Arctic circle. This circumstance leads us to wonder whether 

 the corresponding southern latitudes have ever experienced 

 similar climatic vicissitudes. Conclusive evidence on this point 

 it is difficult to get, but competent biologists who have examined 

 the floras and faunas of South Africa and Australia, of New 

 Zealand, South America, and the isolated islets of the Southern 

 Ocean, find features which absolutely involve the existence of 

 an extensive Antarctic land — a land which must have been 

 clothed with a varied vegetation, and have been alive with 

 beasts, birds, and insects. As it also had had its fresh-water 

 fishes, it must have had its rivers flowing and not frost-bound, 

 and in those circumstances we again see indications of a modified 

 Antarctic climate. Let us briefly consider some of the evidence 

 for the existence of this continent. We are told by Prof, Hutton, 



of Christchurch, that 44 per cent, of the New Zealand flora i 

 of Antarctic origin. The Auckland, Campbell, and Macquaric 

 Islands all support Antarctic plants, some of which appear never 

 to have reached New Zealand. New Zealand and South 

 America have three flowering plants in common, also two fresh 

 water fishes, five seaweeds, three marine crustaceans, one marine 

 mollusk, and one marine fish. Similarly New Zealand and 

 Africa have certain common forms, and the floras and faunas of 

 the Kerguelen, the Crozets, and the Marion Islands are almost 

 identical, although in each case the islands are very small, and very 

 isolated from each other and from the rest of the world. Tristan 

 d'Acunha has 58 species of marine Mollusca, of which number 

 13 are also found in South America, six or seven in New Zealand, 

 and four in South Africa (Mutton's " Origin of New Zealand 

 Flora and Fauna"). Temperate South America has 74 genera 

 of plants in common with New Zealand, and 11 of its species 

 are identical (Wallace's " Island Life "). Penguins of the genus 

 Ejidyptes are common to South America and Australia (Wallace, 

 " Dist. of Animals," 1309). Three groups of fresh-water fishes 

 are entirely confined to these two regions. Aphritis, a fresh-water 

 genus, has one species in Tasmania and two in Patagonia. 

 Another small group of fishes known as the Haplochitonidae 

 inhabit Tierra del Fuegia, the Falklands, and South Australia, 

 and are not found elsewhere, while the genus Galaxias is confined 

 to South Temperate America, New Zealand, and Australia. 

 Yet the lands which have these plants and animals in common 

 are so widely separated from each other that they could not now 

 possibly interchange their inhabitants. Certainly towards the 

 equator they approach each other rather more, but even this fact 

 fails to account for the present distribution, for, as Wallace has 

 pointed out, "the heat-loving Reptilia afford hardly any indica- 

 tions of close affinity between the two regions " of South America 

 and Australia, "whilst the cold-enduring Amphibia and fresh- 

 water fishes ofter them in abundance" (Wallace, "Dist. of 

 Animals," 1400). Thus we see that to the north interchange 

 is prohibited" by tropical heat, while it is barred to the south by 

 a nearly shoreless circumpolar sea. Yet there must have been 

 some means of intercommunication in the past, and it appears 

 certain that it took the shape of a common fatherland for the 

 various common forms from which they spread to the northern 

 hemisphere. As this fatherland must have been accessible from 

 all these scattered southern lands, its size and its disposition 

 must have been such as would serve the emigrants either as a 

 bridge or as a series of stepping-stones. It must have been 

 either a continent or an archipelago. 



But a further and a peculiar interest attaches to this lost 

 continent. Those who have any acquaintance with geology 

 know that the i)lacental Mammalia — that is, animals which are 

 classed with such higher forms of life as apes, cats, dogs, bears, 

 horses, and oxen — appear very abruptly with the incoming of the 

 Tertiary period. Now, judging by analogy, it is not likely that 

 these creatures can have been developed out of Mesozoic forms 

 with anything like the suddenness of their apparent entrance upon 

 the scene. For such changes they must have required a long 

 time, and an extensive region of the earth, and it is probable 

 that each of them had a lengthy series of progenitors, which 

 ultimately linked it back to lower forms. \ 



Why, then, it is constantly asked, if this was the sequence of I 

 creation, do these missing links never turn up ? In reply to this | 

 query, it was suggested by Huxley that they may have been \ 

 developed in some lost continent, the boundaries of which were 

 gradually shifted by the slow elevation of the sea margin on one 1 

 side and its simultaneous slow depression upon the other, so that 

 there has always been in existence a large dry area with its live 

 .stock. This dry spot, with its fauna and flora, like a great raft 

 or Noah's Ark, moved with great slowness in whatever direction 

 the great earth-undulation travelled. But to-day this area, with 

 its fossil evidences, is a sea-bottom ; and Huxley supposes that 

 the continent, which once occupied a part of the Pacific Ocean, 

 is now represented by Asia. 



This movement of land-surface-translation eastwards evf-n- 

 tually created a connection between this land and Africa and 

 Europe, and if when this happened the Mammalia spread 

 rapidly over these countries, this circumstance would account for 

 the abruptness of their appearance there. 



Now, Mr. Blanford, the President of the Geological Society 

 of London, in his annual address, recently delivered, advances 

 matters a staije further, for he tells us that a growing acquaint- 

 ance with the biology of the world leads naturalists to a belief 

 that the placental Mammalia, and other of the higher forms of 



NO. 1094, VOL. 42] 



