August 26, 1880] 



NATURE 



389 



erralic blocks are iml/cJJdJ. It is therefore not improbable that 

 tliey may have been derived from some high land formed of 

 Laurentian rocks of which the outer Hebrides and parts of the 

 mainland of Scotland form surviving portions. If so, then I 

 can conceive of no agent capable of transporting large boulders 

 and dropping them into the Lower Silurian mud of the seas of 

 the time save that of icebergs or other floating ice, and the 

 same view with regard to the neighbouring boulder-beds of 

 Ayrshire is held by Mr. James Geikie. If however any one 

 will point out any other natural cause still in action by which 

 such results are at present brought about, I should be very glad 

 to hear of it. 



I must now turn to India for further evidence of the action of 

 Paleozoic ice. In the Himalayas of Pangi, south-east of Kash- 

 mir, according to Medlicottand Blanford, "old slates, supposed 

 to be Silurian, contain boulders in great numbers," which they 

 believe to be of glacial origin. Another case is mentioned as 

 occuiTing in "transition beds of unknown relations," but in 

 another passage they are stated to be " very ancient, but no idea 

 can be formed of their geological position." The imderlying 

 rocks are markeJ by distinct glacial striations. 



The next case of glacial boulder-beds with which I am ac- 

 quainted is found in Scotland, and in some places in the north 

 of England, where they contain what seem to be indistinctly 

 ice-scratched stones. I first observed these rocks on the Lam- 

 mermuir Hills, south of Dunbar, lying unconformably on Lower 

 Silurian strata, and soon inferred them to be of glacial origin, a 

 circumstance that was subsequently confirmed by my colleagues 

 Prof, and Mr. James Geikie, and is now familiar to other officers 

 of the Geological Survey of Scotland. 



I know of no boulder formations in the Carboniferous series, but 

 they are well known as occurring on a large scale in the Permian 

 brecciated conglomerates, where they consist "of pebbles and 

 large blocks of stone, generally angular, imbedded in a marly 

 paste . . . the fragments have mostly travelled from a distance, 

 apparently from the borders of Wales, and some of them are 

 three feet in diameter." Some of the stones are as well scratched 

 as those found in modem moraines or in the ordinary boulder- 

 clay of what is commonly called the Glacial epoch. In 1S5S 

 the old idea was still not unprevalent that during the Permian 

 •epoch, and for long after, the globe had not yet cooled suffi- 

 ciently to allow of the climates of the external world being uni- 

 versally affected by the constant radiation of heat from its 

 interior. For a long time, however, this idea has almost entirely 

 vanished, and now, in Britain at all events, it is Utile if at all 

 attended to, and other glacial episodes in the history of the world 

 have continued to be brought forward and are no longer looked 

 upon as mere ill-judged conjectures. 



The same kind of brecciated boulder-beds that are found in 

 our Permian strata occur in the Rotheliegende of Germany, 

 which I have visited in several places, and I believe them to 

 have had a like glacial origin. 



Mr. G. W. Stow, of the Orange Free State, has of late years 

 given most elaborate accounts of similar Permian boulder-beds 

 in South Africa. There great masses of moraine matter not 

 only contain ice-scratched stones, but on the banks of rivers 

 where the Permian rock has been removed by aqueous denudation 

 the underlying rocks, well rouuded and mammillated, are 

 covircd by deeply incised glacier grooves pointing in a direction 

 which at length leads the observer to the Pre-Permian mountains 

 from whence the stones were derived that formed these ancient 

 moraines.' 



Messrs. Blanford and Medlicott have also given in "The 

 Geology of India " an account of boulder-beds in what tliey 

 believe to be Permian strata, and which they compare with those 

 described by me in England many years before. There the 

 Godwana group of the Talchir strata contains numerous boulders, 

 many of them six feet in diameter, and in one instance some of 

 the blocks were found to be polished and striated, and the tinder-lying 

 Vindhyan rocks were similarly marked." The authors also corre- 

 late these glacial phenomena with those found in similar deposits 

 in South Africa, discovered and described by Mr. Stow. 



In the Olive group of the Salt range, described by the same 

 authors, there is a curious resemblance between a certain con- 

 glomerate "and that of the Talchir group of the Godwana 



■ Mr. Stows last memoir on tliis subject is still in manuscript. It is so 

 exceedingly long, and tfie sections that accompany it are ot- such unusual 

 size, that the Geological Society could not afford their publication. It was 

 thought that the Government of the Orange Free State might undertake this 

 duty, but the late troubles in South Africa have probably hindered this work 

 — it is to be hoped only for a time. 



system." This "Olive conglomerate" belongs to the Cret.aceous 

 series, and contains ice-transported erratic boulders derived from 

 unknown rocks, one of which of red granite "is polished and 

 striated on three faces in so characteristic a manner that very 

 little doubt can exist of its having been transported by ice." 

 One block of red granite at the Mayo Salt Mines of Khewra " is 

 7 feet high and 19 feet in circumference." In the " Transition 

 beds " of the same authors, which are supposed to be of Upper 

 Cretaceous age, there also are boulder beds with erratic blocks 

 of great size. 



I know of no evidence of glacial phenomena in Eocene strata 

 excepting the occurrence of huge masses of included gneiss in 

 the strata known as Flysch in Switzerland. On this question, 

 however, Swiss geologists are by no means agreed, and I attach 

 little or no importance to it as affording evidence of glacier ice. 



Neither do I know of any Miocene glacier-deposits excepting 

 those in the north of Italy, near Tiu-in, described by the late 

 eminent geologist, Gasioldi, and which I saw under his guidance. 

 These contain many large erratic boulders derived from the 

 distant Alps, which, in my opinion, were then at least as lofty 

 or even higher than they are now, especially if we consider the 

 immense amount of denudation which they underwent during 

 Miocene, later Tertiary, and post-Tertiary times. 



At a still later date there took place in the north of Europe 

 and America what is usually misnamed " 77/t' Glacial Epoch," 

 when a vast glacial mass covered all Scandinavia and distributed 

 its boulders across the north of Germany, as far south as the 

 country around Leipzig, when Ireland also was shrouded in 

 glacier ice, and when a great glacier covered the larger part of 

 Britain and stretched southward, perhaps nearly as far as the 

 Thames on the one side, and certainly covered the whole of 

 Anglesey, and probably the \\ hole, or nearly the whole, of South 

 Wales. This was after the advent of man. 



Lastly, there is still a minor Glacial epoch in progress on the 

 large and almost unknown Antarctic continent, from the high 

 land of ^^•hich in latitudes which partly lie as far north as 60° 

 and 62°, a vast sheet of glacier-ice of great thickness extends far 

 out to sea and sends fleets of icebergs to the north, there to melt 

 in warmer latitudes. If in accordance with the theory of Mr. 

 Croll, founded on astronomical data, a similar climate were 

 transferred to the northern hemisphere, the whole of Scandinavia 

 and the Baltic would apparently be covered with glacier-ice, 

 and the same would probably be the case with the Faroe 

 Islands and great part of Siberia, while even the mountain tracts 

 of Britain might again maintain their minor systems of glaciers. 

 Conclusions. — In opening this address I began with the sub- 

 ject of the oldest metamorphic rocks that I have seen — the 

 Laurentian strata. It is evident to every person who thinks on 

 the subject that their deposition took \>\Oit:e. far from the beginning 

 of recognised geological time. For there must have been older 

 rocks by the degradation of which they were formed. And if, 

 as some American geologists affirm, there are on that continent 

 metamorphic rocks of more ancient dates than the Laurentian 

 strat.!, there must have been rocks more ancient still to afford 

 materials for the deposition of these pre-Laurentian strata. 



Starting with the Laurentian rocks, I have shown that the 

 phenomena of metamorphism of strata have been continued from 

 that date all through the later formations, or groups of forma- 

 tions, down to and including part of the Eocene strata in some 

 parts of the world. 



In like manner I have shown that ordinary volcanic ro.CKS 

 have been ejected in Silurian, Devonian, Carboniferous, Jurassic, 

 Cretaceo-Oolitic, Cretaceous, Eocene, Miocene, and Pliocene 

 times, and from all that I have seen or read of these ancient 

 volcanoes I have no reason to believe that volcanic forces 

 played a more important part in any period of geological time 

 than they do in this our modern epoch. 



So also mountain chains existed before the deposition of the 

 Silurian rocks, others of later date before the Old Red Sandstone 

 strata were formed, and the chain of the Ural before the 

 deposition of the Peimian beds. The last gi'cat upheaval of the 

 Alleghany Mountains took place between the close of the 

 form'ation of the Carboniferous strata of that region and the 

 deposition of the New Red Sandstone. 



According to Darwin, after variLius oscillations of level, the 

 Cordillera underwent its chief upheaval after the Cretaceous 

 epoch, and all geologists know that the Alps, the PjTenees, the 

 Carjiathians, the Himalayas, and other mountain-chains (which 

 I have named) underwent what seems to have been their chief 

 great upheaval after the deposition of the Eocene strata, while 



