420 



NATURE 



\Sept. I, 1 88 1 



advanced to deal " with questions as to the origin of things," he 

 saw that a great body of new data were required, such as engaged 

 the attention of the Geological Society (founded in 1807), and 

 which, along with other foreign societies and private work, 

 has at length brought geological science to its present high 

 position. 



And what is that position? With great and consentient labour, 

 many men, gifted with a knowledge of stratigraphical and paleeon- 

 tological geology, have, so to speak, more or less dissected all 

 the regions of Europe and great part of North America, India, 

 and of our colonies, and in vast areas, sometimes nearly adjoin- 

 ing, and sometimes far distant from each other, the various 

 formation^, by help of the fossils they contain, have been corre- 

 lated in time, often in spite of great differences in their litho- 

 logical characters. It is easy, for example, to correlate the 

 various formations in countries so near as Great Britain and 

 Ireland, or of the Secondary and Lower Tertiary formations of 

 England and France ; and what is more remarkable, it is easy 

 to correlate the PaL-eozoic formations of Britain and the eastern 

 half of the United States and Canada, even in many of the 

 comparatively minute stratigraphical and lithological subdivisions 

 of the Silurian, Devonian, and Carboniferous formations. The 

 same may be said with regard to some of the Palseozoic formations 

 of India, China, Africa, and Australia, and many of the 

 Secondary and Tertiary deposits have in like manner been identi- 

 fied as having their equivalents in Europe. It is not to be 

 inferred from these coincidences that such deposits were all 

 io'cxazA pi-ecisdy at the same time, but taken in connection with 

 their pakxontological contents, viewed in the light which Darwin 

 has shown with regard to the life of the globe when considered 

 in their relation to masses of stratified formations, no modern 

 geologist who gives his mind to such subjects would be likely 

 to state, for example, that in any part of the globe Silurian 

 rocks may be equivalents in time to any of our Upper PalEEozoic, 

 Mesozoic, or Tertiary formations. 



For all the latest details of genera and species found in the 

 British Paljeozoic rocks, from those of St. David's, so well 

 worked out by Dr. Hicks, to the Carboniferous series inclusive, 

 I must refer to the elaborate address of Mr. Etheridge, Pre- 

 sident of the Geological Society, which he delivered at the last 

 anniversary meeting of that society. It is a work of enormous 

 labour and skill, which could not have been produced by any one 

 who had not a thorough personal knowledge of all the formations 

 of Britain and of their fossil contents." 



In connection with such subjects I will not in any h ay deal 

 with the tempting and important subject of cosmological geology, 

 which in my opinion must go back to times far anterior to the 

 date of the deposition, as common sediments, of the very oldest- 

 known metamorphic strata. Cosmological speculations perhaps 

 may be sound enough with regard to I'efrigeration, and the first 

 consolidation of the crust of the earth, but all the known tan- 

 gible rocky formations in the world have no immediate relation 

 to them, and in my opinion the oldest Laurentian rocks were 

 deposited long after the beginning and end of lost and unknown 

 epochs, during which stratified rocks were formed by watery 

 agents in the same way that the Laurentian rocks were deposited, 

 and in which modern formations are being deposited now, and 

 the gneissose structure of the most ancient formations Mas the 

 result of an action which has at intervals characterised all geolo- 

 gical time as late as the Eocene formations in the Alps and 

 elsewhere. 



The same kind of chronological reasoning is often applicable 

 to igneous rocks. It was generally the custom, many years ago, 

 to recognise two kinds of igneous rocks, viz., Volcanic and 

 Plutonic, and this classification somewhat modified in details 

 is still applicable, the Plutonic consisting chiefly of granitic 

 rocks and their allies, and which though they have often altered 

 ani thrust veins into the adjoining strata, have never, as far as 

 I know, overflowed in the manner of the lavas of modern and 

 ancient volcanoes. Indeed, as far as I recollect, the first quoted 

 examples of ancient volcanoes are those of Miocene age in the 

 districts of Auvergne, the Velais, and the Eifel, and the fact that 

 signs of ordinary volcanic phenomena are found in almost all 

 the larger groups of strata \\as scarcely suspected. Now, 

 however, we know them to be associated with strata of all or 

 almost all geological ages, from Lower Silurian times down to 

 the present day, if we take the whole world into account. 



" I must also, with much pleasure, advert to Prof. Prestwich's inaugural 

 lecture when installed in the Chair of Geology at Oxfoid in 1875, the subject 

 of which is "The Past and Future of Geology. " 



Amongst them, those of Miocene date hold a very prominent 

 place, greatly owing, doubtless, to the comparative perfection 

 of their forms, as, for example, those 6f the South of France 

 and of the Eifel. Their conical shapes, and numerous extinct 

 craters, afford testimony so plain, that he who runs may read 

 their history. The time when they became extinct would 

 doubtless amaze us by its magnitude, if it could be stated in 

 years, but yet it is comparatively so recent that not all the 

 undying forces of atmospheric degradation have been able to 

 obliterate their individual origin. 



It is, however, generally very different \\ith respect to 

 volcanoes of Mesozoic age, for though Lyell stated with doubt, 

 that volcanic products of Jurassic date are found in the Morea 

 and in the Apennines ; and Medlicott and Blanford consider that 

 probably the igneous rocks of Rajmahal may be of that age, we 

 must, perhaps, w ait for further information before the question 

 may be considered as finally settled. Of Jurassic age no actual 

 craters remain. Darwin also has stated, on good grounds, that 

 in the Andes a line of volcanic eruptions has been at work from 

 before the deposition of the Cretaceo-oolitic formation down to 

 the present day. 



In the British Islands we have a remarkable series of true 

 volcanic rocks, the chronology of which has been definitely 

 determined. The oldest of these belongs to the Lower Silurian 

 epoch, as shown, for example, on a large scale in Pembrokeshire, 

 at Builth in Radnorshire, in the Longmynd country west of the 

 Stiper stones in Shropshire, and on a far greater scale in North 

 Wales and Cumbria. Of later date we find volcanic lavas and 

 ashes in the Devonian rocks of Devon, and in the Old Red 

 Sandstone of Scotland. The third series is plentiful among the 

 Carboniferous rocks of Scotland, and in a smaller way in- 

 terstratified with the Coal-measures of South Staffordshire, 

 Warwickshire and the Clee Hills. The fourth series chrono- 

 logically is associated with the Permian strata in Scotland, and 

 the fifth and last consists of the Miocene basaltic rocks of the 

 Inner Hebrides and the mainland of the West of Scotland. 



In the British Islands the art of geological surveying has, I 

 believe, been carried out in a more detailed manner than in any 

 other country in Europe, a matter which has been rendered 

 comparatively easy by the excellence of the Ordnance Survey 

 maps both on the I -inch and the 6-inch scales. When the 

 whole country has been mapped geologically little will remain 

 to be done in geological surveying, excepting corrections here 

 and there, especially in the earliest published maps of the 

 South-west of England. Palseontological detail may, however, 

 be carried on to any extent, and much remains to be done 

 in microscopic petrology which now deservedly occupies the 

 attention of many skilled observers. 



Time will not permit me to do more than advert to the 

 excellent and well-known geological surveys now in action in 

 India, Canada, the United States, Australia, New Zealand, and 

 South Africa. 



On the Continent of Europe there are National Geological 

 Surveys of great and well-deserved repute conducied by men of 

 the highest eminence in geological science, and it is to be hoped 

 the day may come when a more detailed survey will follow the 

 admirable map executed by Sir Roderick Murchison, De 

 Verneuil, and Count Keyserling, and published in their joint 

 work, "The Geology of Russia in Europe and the Ural 

 Mountains." 



It is difficult to deal with the Future of Geology. Probably 

 in many of the European formations more may be done in 

 tracing the details of subformations. The same may be said 

 of much of North America, and for a long series of years a 

 great deal must remain almost untouched in Asia, Africa, South 

 America, and in the islands of the Pacific Ocean. If, in the far 

 future, the day should come when such work shall be undertaken, 

 the process of doing so must necessarily be slow, partly for 

 want of proper maps, and possibly in some regions partly for 

 the want of trained geologists. Palaeontologists must always 

 have ample w ork in the discovery and description of new fossils, 

 marii.e, freshwater, and truly terrestrial ; and besides common 

 stratigraphical geology, geologists have still an ample field 

 before them in working out many of those physical problems 

 which form the true basis of Physical Geography in every 

 region of the earth. Of the history of the earth there is a 

 long pa.st, the early chapters of w^hich seem to be lost for ever, 

 and we know little of the future except that it appears that 

 " the stir of this dim spot which men call earth," as far as 

 Geology is concerned, shows " no sign of an end." 



