504 



NA TURE 



{Sept. 20, 



knowledge in the discussion of the questions brought before the 

 International Congress. The number of geologists present on 

 this its fourth meeting indicates the continued and deep interest 

 that they take in it. 



Among the more permanent officers are the Secretaries of the 

 Congress and of its Committees to whose important and gratuitous 

 services we are so deeply indebted. We have unfortunately to 

 deplore the untimely death of one amongst them — M. Charles 

 Fontannes — and we lose on this occasion the benefit of his long 

 experience and valuable aid. 



According to custom, our discussions are, as in the diplomatic 

 world, held in French ; but it is to be hoped that the entente 

 cordiale will be better maintained than it sometimes is in the 

 other case, where such councils have not always succeeded in 

 avoiding strife. If I may be permitted to speak after an expe- 

 rience of half a century, an etttente of the most cordial character 

 between us English geologists and our colleagues and friends 

 abroad has been during these long years the normal condition. 

 May these friendly and loyal relations prove a legacy to our 

 science for all time. These friendly meetings were, however, 

 only occasional, so that the opportunities for personal inter- 

 change of ideas were few. But more lately, instead of discuss- 

 ing unsettled questions, each nationality apart, the happy idea 

 arose of submitting certain questions, which concern us all, to 

 the arbitration of this General Council. In this manner the 

 different national centres of our science, which have each their 

 local colouring and their special experience, are enabled to com- 

 bine the results arrived at in a wider and more uniform manner 

 than if each apart worked out its ideas, based necessarily on 

 more restricted observations. Nevertheless, in giving to our 

 science the uniformity of terms and of classification which is so 

 necessary, care must be taken not to draw lines too tight, such 

 as, instead of developing, might retard its progress. It is desir- 

 able that these lines should be so elastic as to adjust themselves 

 to the rapid development we have reason to expect in geological 

 science. It is highly necessary that we should agree upon the 

 colours and symbols to be used for the different strata, rocks, 

 and disturbances that the terrestrial crust presents to us, but 

 petrology is still far from being placed on firm foundations, and 

 the synchronism of the beds, even between near countries, is 

 not always easy to determine with exactitude, and still less 

 between distant countries. Let us then try to avoid that error 

 of Congresses — of arrogating an infallibility which is little in 

 accordance with the progress of science. 



Let me now say a few words upon what the Congress has 

 already accomplished, and on what remains to be done. 



At Bologna, Prof. Capellini gave the history of the Congress 

 so fully that there is no need that I should speak of it unless it 

 be to remind you that the idea of the Congress originated in 

 America at the Exhibition of Philadelphia in 1876, and doubt- 

 less this idea, as well as that of the Exhibition itself, was only 

 the expression of a desire that had been very generally felt for 

 some time, to treat certain questions of science and art, not only, 

 so to speak, in a national family reunion, but in a cosmopolitan 

 reunion — to treat the great questions that concern all humanity, 

 as belonging to the whole civilized world, and for the purposes 

 of discussion, to make of the various nationalities a brotherhood, 

 established on their common interests and their common weal. 



The Paris Congress. — At the first Congress, which met 

 in Paris in 1878, the primary questions of nomenclature and 

 of classification were sketched out, as well as the unification 

 of geological works with regard to colours and figures, so 

 that in all countries their signification should be the same. 

 A proposal, which was at first well received, was to make 

 use of the solar spectrum, and to adopt the three primary 

 colours — red, blue, and yellow — for the three divisions of 

 the first rank of Primary, Secondary, and Tertiary rocks ; 

 that the subdivisions of the second order should be dis- 

 tinguished by shades of these colours, and those of the third 

 order by hatchings of these same colours. But subsequently this 

 scale was found to be too restricted, and at Bologna and Berlin 

 several modifications and complementary colours were intro- 

 duced, although always retaining to a certain degree the original 

 idea. As a corollary it has been suggested that the labels of 

 fossils should, as has already been done in several Museums, be 

 of the same colour as that used for the strata from which they 

 come, and that thus one would at a glance see the horizon and 

 age of the fossil. 



As to the question of unification of nomenclature for the great 

 divisions of the eartrris crust, it was felt that it is in the first 



place essential that there should be perfect agreement about the 

 terms in use, and therefore that a dictionary of geology compris- 

 ing the etymology or the origin of each geological name, its 

 synonym in other languages, a definition in French, and a 

 demonstrative figure after the manner of technological diction- 

 aries, would be of very great use. The publication of such a 

 work, which ought to be in at least six languages, was strongly 

 supported. Finally, the consideration of the foregoing questions 

 was referred to the International Commissions to report upon to 

 the meeting of the Bologna Congress. 



With regard to the classification of the strata, memoirs were 

 received upon the Pre-Cambrian rocks, and on the nomenclature 

 of the Palaeozoic strata of North America ; on the limits of the 

 Carboniferous and Permian in various parts of Europe and in 

 America ; on the relations of the zones of extinct Vertebrates in 

 North America and in Europe ; these two last memoirs being 

 accompanied by valuable lists of Invertebrates, plants, and 

 reptiles of different countries. These memoirs raised very im- 

 portant stratigraphical and palseontological questions with regard 

 to the wide distribution of families and of genera. Each of the 

 faunas of the primary divisions of geological periods has been in 

 part recognized as occurring at the same time in the two 

 continents — in Europe and in North America : and Prof. Cope 

 has been led to inquire whether the organic types proceed from 

 a special centre from which ihey have spread ; or whether the 

 same types of generic structure have appeared independently at 

 different points of the surface of the globe ; and if so, whether 

 they are contemporary or of varying periods. These synchronous 

 appearances form a subject full of mystery, from whatsoever side 

 they may be viewed. The geological record is at present too in- 

 complete for the problem to be solved. In each country there 

 are gaps that can only be filled by aid of continued observations 

 in the other parts of the world. One of the most useful functions 

 of the Congress is to encourage these. 



The classification of Quaternary deposits was also discussed 

 in relation to the remarkable history of the caves of Central 

 France ; the glacial deposits and dunes of Holland ; the 

 Tertiary beds of Portugal, which are limited to the Miocene and 

 Pliocene ; the Tertiary eruptive rocks of Hungary, viewed as 

 to whether there is not a certain relation between the minera- 

 logical constitution and the relative age of the various trachytic 

 types. 



The Congress was also occupied with some high physical 

 questions, such as those of the deformations and fractures of the 

 earth's crust ; the strike and dip of faults and of chains of 

 mountains ; the origin of volcanoes, and the probable causes of 

 great earthquakes ; the structure of the Alps, and the folds of the 

 Chalk. 



Less in connection with the fundamental objects of the Con- 

 gress, but having nevertheless an interest of their own, were the 

 memoirs on the feldspars, on the alteration of the superficial de- 

 posits, on the use of the polarizing microscope, on the conductivity 

 of heat in rocks, and other special subjects. 



The Bologna Congress. — In the handsome volume of the 

 Proceedings of the Session at Bologna, will be found the Report 

 of the International Jury appointed to judge the competing 

 memoirs on the unification of colours and geological signs, 

 towards which the King of Italy generously gave 5000 francs to 

 be awarded to the best memoir considered practically applicable. 

 Six memoirs were received, of which the three selected for the 

 award are published with coloured illustrations which leave 

 nothing to be desired. The authors of these papers were of opinion 

 that although the solar spectrum offers a very advantageous fixed 

 base, the scale of colours is insufficient, and that it would be 

 necessary to introduce complementary colours, or those having 

 relation to the primary colours. The divisions, in short, of the 

 sedimentary strata are so numerous that it will be necessary, not 

 only to employ those colours, but also several shades of the same, 

 or different hatchings, in reserving rose colour for the crystalline 

 Archaean schists. For the eruptive rocks, they all agreed to use 

 dark and bright tints of red, green, and purple, the intensity of 

 which will render them to be readily distinguishable from the 

 primary colours of the sedimentary rocks and from the clear 

 colour of the schists. It was attempted to distinguish the acid 

 and basic rocks, both with respect to their penological com- 

 position and their age, by the use of different tints of the same 

 colours in coloured dots, or by hatchings of various patterns, and 

 with the letters of the Greek alphabet. Thus it is proposed to 

 show by signs the principal varieties of granitic, porphyrinic, 

 trachytic, andesitic, and basaltic rocks, &c. ; but the varieties 



