Sept. 28, 1S88.] 



SCIENTIFIC NEWS. 



\M 



Mont Blanc, with the enormous development of the 

 quartzites of Tarantaise and the Valais. 



Professor J. Lehmann contributed a critique on certain 

 recent researches and speculations on crystalline schistous 

 rocks. 



Dr. A. Michel Levy discussed the origin ot the primi- 

 tive crystalline formation. 



Dr. A. C. Lawson, of the Geological Survey of Canada, 

 considered the Archaean geology of the region north-west 

 of Lake Superior. 



G. F. Becker, of the U.S. Geological Survey, treated of 

 the crystalline schists of the coast ranges of California. 

 He observed that the crystalline schists of the coast 

 ranges are mingled with crystalline rocks which cover 

 thousands of square miles. A great portion of these 

 rocks were laid down as sedimentary during the Neo- 

 comian. Soon afterwards they were upheaved with 

 extreme violence, and were subjected to the action of 

 magnesian solutions, probably approaching to tempera- 

 tures above the average, and perhaps approaching the 

 boiling point. 



Professor Lory, in opening the discussion, spoke on 

 the crystalline schists of the Western Alps. He pointed 

 out that they were composed of a regular series of 

 assises of constant mineralogical characters. Their struc- 

 ture was independent of dislocations. One crucial 

 observation for any one seeking to explain their mode of 

 origin was furnished by the existence of crystallised 

 silicates in the secondary and tertiary formations of the 

 Alps; garnets, mica, tourmaline, in the schists of the 

 Trias ; and crystals of albite in the Eocene limestones. 

 They were thus formed in the crystalline silicious rocks 

 of every epoch. The presence of these crystals had no 

 connection with the intensity of the mechanical move- 

 ments, for they were even found in horizontal beds. The 

 crystals were formed in each geological epoch shortly 

 after the period of sedimentation, and their development 

 was connected with the mode and formation of the rocks 

 themselves, and depended upon the original conditions 

 of the deposit. He agreed with the theory of the hydro- 

 thermal origin of the crystalline schists. 



Mr. Mattirolo gave some interesting details about a 

 metamorphic Permian rock widely distributed in the 

 Western Alps and Apennines. It presented a gneissic- 

 porphyritic structure, and he had classified it under the 

 name of Besimandite. 



Mr. M'Farlane declared himself a Plutonist, and read 

 to the Congress his opinions on the origin of the crystal- 

 line schists. 



Professor Issel insisted on the analogies which his 

 observations presented with those of M. Lory. The 

 schists and nummulitic limestones with crystallised sili- 

 cates owed their origin to hydrothermal action. This 

 most assured fact put us in sight of a rational explana- 

 tion of the formation of the crystalline schists. 



Professor Heim remarked that many questions pre- 

 sented themselves to any one beginning the study of 

 crystalline schists. They had been subjected to general 

 metamorphism, to modifications by contact, and by me- 

 chanical contortions. It was, therefore, an advantage to 

 seek the key of the problem in the study of the trans- 

 formed sedimentary rocks. In the two cases, in fact, 

 common characters of structure might be observed — 

 cleavages, entirely linear, surfaces, contortions, etc. 

 These sedimentary formations, mechanically contorted 

 into synclinal curves, contained crystallised silicates. 

 They were analogous to those which were developed by 



metamorphism of contact; but they could not in this 

 case be attributed to that cause. The extent of the me- 

 chanical phenomena was the predominant fact in the 

 Alps, and it complicated the study of the subject. In the 

 parts of the earth less affected by mechanical contortions 

 one might hope to find an explanation of the origin of 

 the schists. 



Dr. Sterry Hunt declared himself to be a disciple of 

 Werner. He believed that the old granites as well as 

 the basic gneisses were of aqueous origin and were 

 chemically deposited. This action had continued since 

 the most remote period, and was going on at the present 

 day with diminished intensity. 



Dr. Hicks said that the crystalline schists, when they 

 occurred over a great area, were, he believed, invariably 

 of the pre-Cambrian age. He believed that the massive 

 gneisses were originally igneous rocks which had under- 

 gone much change. The mica and chloritic schists he 

 believed to have been formed mainly from volcanic ashes 

 and muds. He admitted that rocks of volcanic origin 

 could change at any period of the world's history into 

 crystalline schists under favourable conditions, such as 

 pressure, mechanical movement, and percolations of 

 liquid. The detrital rocks would show certain im- 

 portant changes, but only partially simulated the older 

 rocks. The porcellanites, quartzites, and clay slates 

 were detrital rocks. Sediments repeatedly deposited 

 gradually lost their power of complete changes, hence 

 the crystalline schists were mainly of pre-Cambrian. 

 The Pebidian rocks in Wales yielded most instructive 

 evidence in support of the above views. 



M. de Lapparent, who now occupied the chair in the 

 place of Dr. Geikie, explained very summarily his per- 

 sonal views on the primitive formation. The formation 

 had a distinct existence, it was independent of the fol- 

 lowing periods, and the explanation of its origin should 

 be found in the combination of chemical, mechanical, and 

 calorific actions carried on to their maximum. 



Professor O. Torell explained that he had distinguished 

 in Sweden two granites, one eruptive and the other 

 ancient, passing into gneiss. 



Mr. M'Pherson called attention to the regularity pre- 

 sented by the succession of three great groups of crystal- 

 line schists in Spain — 1, granitoid gneiss at the base ; 

 2, micaceous gneiss with limestone; and, 3, mica schists. 

 M. de Lapparent, in closing the discussion, referred 

 to the facts collected in the published memoirs of the 

 English Committee. 



On Thursday the question discussed was, whether for 

 the period immediately preceding the present, the term 

 Quaternary should be used as of equal value with 

 Secondary, Tertiary, etc., or the period should be called 

 Pleistocene, and considered as merely a part of the 

 Tertiary. The term Quaternary has found much more 

 favour on the Continent than in Great Britain, where the 

 Lyellian name, Pleistocene, is almost universally adopted. 

 As might have been expected, the foreign geologists 

 mostly were in favour of Quaternary. This, however, 

 was not universal, Professor Renevier, of Lausanne, 

 who began the discussion, adhering to the term Pleisto- 

 cene as a division of the Tertiary. This opinion he held, 

 because no important organic type marked the period 

 except the appearance of man, and this fact would not be 

 considered as fully established. The glacial period 

 also is not characteristic of the period, because it 

 began in the Pliocene, or perhaps before. 



