204 TEAXSACTIOXS OF THE SOCIETY OF 



served, according to the degree of concentration of the solution. The metals 

 on whicli these experiments were made are didyme, erbium, and terbium. 



Dr. W. Marcet read two memoirs : one on a colloid acid derived from urine, 

 in which some new details were added respecting the chemical properties and 

 atomic weight of this acid ; the second memoir {Bib. Univers., Archives, &c., 

 vol. xxii) had for its object the muscular dialysis, M. Marcet proving in this 

 paper that the muscular substance is permeable for colloid as well as crystal- 



lizable. substances. M. Chaix offered some remarks on the accumulation 



of volcanoes, whether extinct or in activity, with which recent explorations 

 have made us acquainted in certain regions of the globe, particularly in the re- 

 public of Nicaragua and in New Zealand. He also indicated, on the authority 

 of a memoir of M. Abich, the appearance of several new islands, which have 

 emerged in the Caspian sea, as a sequel of volcanic movements in 1857 and 



1864. Dr. Pitschner read an account of his ascension of Mont Blanc in 



1859, during which he took occasion to make observations on different points of 

 terrestrial physics, physiology, and zoology. 



NATURAL SCIENCES. 



Professor Favre presented to the society a memoir, [Bib. Univers., Archives, 

 &c., vol. xxii,) in which he recapitulates, from an historical point of view, the 

 discussion which has taken place on the subject of the coal formation of the 

 Alps, and announces the conclusions at which he has arrived from his observa- 

 tions made in different parts of those mountains. The study of the chain of 

 Mont Blanc formed the subject of two memoirs read by M. Favre ; in the first, 

 lie occupies himself with the fan-shaped structure of that group, and after having 

 discussed the different theories advanced on this subject, he concurs in the 

 opinion pronounced by M. Lory, adding some cousid^'rations on the protogene 

 of which the chain is formed. In the other memoir he undertakes to investi- 

 gate the succession and thickness of the strata which must have covered that 

 part of the surface of the earth before the, mass of Mont Biauc made its appear- 

 ance and upheaved the formations which covered it. These formations have 

 been gradually removed by the action of atmospheric agents, and thence has 

 resulted an enormous denudation, laying bare the protogene. M. Favre seeks 

 to calculate the volume gauged by the formations thus removed, and he shows 

 that the greatest elevation of the chain, before these denudations, may explain 

 in part the greatest extension of the glaciers. Our colleague, lastly, read to the 

 society his letter, [Bib. Universellc, Archives, &c., vol. xxii,) addressed to Sir R. 

 Murchison, in which he combats the theory of the excavation of the alpine 

 lakes and valleys by glaciers. It was the study of the lake of Geneva and of 

 the direction of the geological strata on the two shores, whether in the eastern 

 or western part, which furnished M. Favre with proof that the depression of the 

 bed of the lake must have proceeded from a cause Avholly different from an ex- 

 cavation by glaciers. 



Professor Pictet presented a memoir [Bib. Univers., Archives, &c., vol. xxi) 

 on the succession of gasteropod mollusks in the cretaceous lakes of the Jura and 

 the Swiss Alps. The study of the fossils collected at Sainte Croix has enabled 

 him to recognize in that locality the existence of nine successive faunas, inde- 

 pendent of one another and almost without mixture, between the epoch of the 

 lower valangian and that of the chloritic chalk of Rouen. A comparison with 

 the cotemporaneous faunas of the neighboring countries shows that the species 

 are there associated somewhat differently, and hence M. Pictet concludes, from 

 analogy with what occurs in our present seas, that we cannot consider each 

 species as characteristic of the whole of a period. It must rather be admitted, 

 contrary to an opinion quite widely entertamed, that the greater part of species 

 have a variable signification, according to the geographic region where they are 



