TBANSACTIONS OF SECTION C. 607 



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 adjoining, 

 and sometimes far distant from each other, the various formations, by help of the 

 fossils they contain, have been correlated in time, often in spite of great differences 

 in their lithological 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 re- 

 markable, it is easy to correlate the palfeozoic 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 ma)'- be said with regard to some of the 

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

 secondary and tertiary deposits have in like manner been identified as having their 

 equivalents in Europe. It is not to be inferred from these coincidences that such 

 deposits were all formed jn-eciseh/ at the same time, but taken in connection with 

 their palseontological contents, viewed in the light which Darwin has shown with 

 regard to the life of the globe when considered in its relation to masses of 

 stratified formations, no modern geologist who gives his mind to such subject-s 

 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 Palaeozoic, Mesozoic, or Tertiary 

 formations. 



For all the latest details of yenera and species found in the British Palteozoic 

 rocks, from those of St. David's, so well worked out by Dr. Hicks, to the Carbon- 

 iferous series inclusive, I must refer to the elaborate address of Mr. Etheridge, 

 President 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 anyone who had not a thorough personal knowledo-e 

 of all the formations of Britain and of their fossil contents.' 



In connection with such subjects I will not in any way 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 the refrigeration, and the first consolidation of the 

 crust of the earth, but all the known tangible 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 was the 

 result of an action which has at intervals characterised all geological 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, which, though they have often altered and thrust veins into the ad- 

 joining 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 Auver^ne, 

 the A elay, and the Eifel, and the fact that signs of ordinary volcanic phenomena 

 are found in almost all the larger groups of strata was 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 wliole 

 world into account. 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 of the South of France and of the Eifel. Their conical shapes, 



' I must also, with much pleasure, advert to Professor Prestwich's inaugural 

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

 which is ' The Past and Future of Geology.' 



