352 



NATURE 



[August 12, 1897 



torrid ; it only illustrates the fact that the order was a primi- 

 tive type once very widely spread throughout the world, and now 

 restricted by the competition of more specialised types. There- 

 fore the occurrence in the Cretaceous rocks of Greenland of the 

 tree-fern Dicksoiiia, which, although it still lives in New 

 Zealand, is said to be most characteristic of the tropical parts of 

 Northern Queensland, is no proof that the Arctic regions had a 

 tropical climate. And it would not be so, even if Sir J. D. 

 Hooker had not warned us, that ferns are the least trustworthy 

 witnesses as to climatic conditions. 



Hence an examination of the evidence of the fossil plants of 

 the Arctic regions leads to three conclusions : (i) that, as curreni 

 opinion rests on Heer's determination of fossil palms and tropical 

 leaves which cannot now be supported, the changes of climate 

 have been greatly exaggerated ; (2) that without a complete 

 revision of Heer's work, such as is now being carried out by 

 Prof. Nathorst, the exact extent of the climatic changes cannot 

 be estimated ; (3) that the conclusions based on the belief that 

 three months' darkness would be fatal to the growth of trees, 

 cannot be maintained, while most of the fossil tree trunks in 

 question have probably been brought as drift wood from the 

 south. 



The fossil faunas of the Arctic regions have been held to 

 demonstrate climatic changes no less enormous than do the 

 fossil floras. The most striking proofs quoted were the asserted 

 occurrence of fossil coral reefs in the Silurian and Carboniferous 

 rocks of various parts of the Arctic area, notably Bank's Land, 

 Grinnell Land, Spitsbergen, and the New Siberian Islands. It 

 is, perhaps, the best-known fact in the science of geographical 

 distribution that coral polypes cannot build coral reefs in water 

 of a lower temperature than 68° F. If, therefore, coral reefs 

 formed by madreporarian corals do occur in the Arctic regions, 

 this would be conclusive evidence of a great change in the 

 temperature of the northern ocean. Let us take the case of the 

 corals of Grinnell Land, of which specimens were brought home 

 by Colonel Feilden, and determined by Mr. Etheridge. The 

 collection included eleven species ; of these six were simple 

 corals, one was a simply branching, another was a cluster of 

 simple corals, and the remaining three species, although com- 

 pound, occurred in small nodules. Of corals in the condition of 

 reef builders, there are none in the collection. Simple corals 

 live in the Arctic ocean at the present day, while compound 

 corals as large as the specimens from Grinnell Land are found 

 far outside the range of existing coral reefs, and at far greater 

 depths. The collection from Grinnell Land gives no proof that 

 coral reefs were ever formed there. We have only to compare 

 the few insignificant species from that region, with the massive 

 corals that lived at the same time in English seas, to realise that 

 there was almost as great a difference between the temperature 

 of the sea in the two areas in Silurian times as there is to-day. 

 Baron von Tol's list of Anthozoa from the Silurian rocks of the 

 New Siberian Islands also includes eleven species ; but of these 

 only three are true Madreporaria. Compound Ilydrozoa and 

 Alcyonaria have a greater range than the reef- building Madre- 

 poraria, both in latitude and depth. Hence, in arguing from 

 the distribution of the fossil corals, we must eliminate all except 

 Madreporaria ; and the moment we apply this rule to the New 

 Siberian coral reefs, we lose all but a few small Madreporaria, 

 which certainly cannot be described as forming reefs. 



If limestones as full of corals as the Silurian rocks of Wen- 

 lock Edge, or some of the beds in the Carboniferous series at 

 Clifton, be ever found north of 80° N. lat., they will no doubt 

 prove that at the time of their formation the Arctic Ocean was 

 a coral sea. But the evidence so far seems insufficient. That 

 the northern seas had a warmer temperature at some parts of 

 the Palaeozoic era than at present is not denied. It is proved 

 by the occurrence of coral reefs in various parts of Europe and 

 America ; and in places massive corals grew as far north as the 

 Arctic Circle, as in the Timan Mountains, and sometimes even 

 a few degrees beyond, as in Bank's Land. But the northern 

 coral faunas are poorer than those of temperate Europe, and 

 as we go nearer the pole, they become so stunted that they 

 ceased to form reefs. 



The corals alone, therefore, are insufficient to prove the uni- 

 versality of a tropical climate in early geological times, and it 

 is advisable to consider the evidence of the fossil faunas as a 

 whole. Arctic marine faunas are known from six of the geo- 

 logical systems— the Silurian, Devonian, Carboniferous (in- 

 cluding Permian), Triassic, Jurassic and Cretaceous. The six 

 faunas are characterised by the following general features : — 



(1) They are often rich in individuals, but poor in species. 



(2) Crustacea, trilobites, zoophytes, and other animals with 

 chitinous exo-skeletons are proportionately common and ofteri 

 large in size. 



(3) Compound corals are scarce, and occur in i>odales rnstead 

 of in reef-forming masses. 



(4) Sea-urchins and sea-lilies are extremely scarce — in fact, 

 barely represented. 



(5) There is a striking poverty in new or special types. 



But these are, in the main, the characteristics of the existing 

 Arctic fauna ; and it is difficult to compare the Arctic fauna of 

 any one period with that which then lived in southern Europe,, 

 without concluding that all through geological time the northern 

 faunas have lived under the blight of Arctic barrenness. 



This reminds us of the question of the shifting of the position 

 of the pole, which was proposed as a help to pakeontologists. 

 in explaining the former Arctic faunas and floras. But the 

 facts seem explicable without the aid of this hypothesis. Neu- 

 mayr has published a map of the probable climatic zones in 

 the Jurassic period, which appear to have been as parallel to- 

 the equator then as they are now. In Tertiary times the evi- 

 dence of the fossil plants seems to show the same ; for, from 

 whatever direction we approach the pole, the fossil floras be- 

 come sparser and more boreal in aspect, as we may see by a 

 comparison of the plants of Disco Island and Grinnell Land, of 

 the Great Slave Lake and Prince Patrick Land, of Iceland and 

 Spitsbergen, and of Saghalien and New Siberia. 



Hence the palasontological evidence, instead of demanding 

 the shifting of the pole, seems to be opposed to this theory, 

 and to show that, in all the periods for which pakeontological 

 evidence is available, the pole stood near its present position. 

 Palreontological evidence, moreover, when freed from sensational 

 exaggeration, shows that the variations in the climate of the 

 Arctic region have not been so extreme as have been assumed, 

 and thus it greatly simplifies the discussion of the causes of the 

 changes that have occurred. The size of the Palaeozoic sun was 

 increased to warm the Arctic Ocean up to the temperature of 

 a coral sea ; the pole was shifted to remove the fatal spell of 

 Arctic night, and clothe parts of the polar lands in subtropical 

 forests. When Lyell proposed to explain the climatic variations 

 by alterations in the position of land and water, he called upon 

 his theory to account for the alternation of a vast polar ice-cap- 

 with tropical conditions. Such results could not be explained by 

 the geographical theory, which accordingly fell into disrepute. 



But if we call upon that theory to explain changes for which 

 there is valid evidence, it is not improbable that it may not 

 suffice. A different distribution of land and sea, a greater or 

 less elevation of the mountain ranges, a deflection of the ocean 

 currents, the reduction of the ice-covered sea, and the meteor- 

 ological changes that would be thus produced may, as Lyell 

 thought, be quite sufficient to account for all the climatic vari- 

 ations which the facts of Arctic geology require. 



J. W. Gregory. 



THE IRON AND STEEL INSTITUTE. 

 'X'HE annual summer meeting of the Iron and Steel Institute 

 -*■ was held last week at Cardiff. The President this year is- 

 Mr. E. P. Martin, who is at the head of the executive of the 

 great Dowlais Iron Works ; and it was appropriate, therefore, 

 that the meeting should be held in the commercial metropolis of 

 Wales. The meeting was in every respect most successful, 

 though certainly it fell off somewhat from a technical point of 

 view ; but that, after all, was largely due to tlie weather, it 

 being too hot to sit in a lecture theatre and discuss details of 

 iron and steel manufacture. An unusually large number of 

 members attended, and many of them were accompanied by 

 ladies. 



On the members assembling on Tuesday morning, the 3rd 

 inst., they were welcomed by the Mayor of Cardiff, after which 

 Mr. Martin took the chair, and other formal business having 

 been transacted, Mr. Thomas Wrightson's paper, "On the 

 Application of Travelling Belts to the Shipment of Coal," was 

 read. In this he described a new method of placing coal into a 

 ship, expeditiously and without breaking it. The latter is a 

 very important point, as small coal or dust is worth very little ; 

 and the old-fashioned method of shooting coal from a staith 

 direct into the hold of a vessel, leads to the formation O'f a great 

 deal of small coal. The apparatus Mr. Wrightson has designed. 



NO. 1450. VOL. 56] 



