GENEVA SOCIETY OF PHYSICS AND NATURAL HISTORY. 231 



panied witli numerous raised sections, prepared with the greatest care, 

 so as to represent the country in all its details. The inversions of the 

 strata are so numerous in this region as to be almost the normal condition ; 

 not less than thirty-six geological stages may be counted in this chart, 

 from the crystalline schists to the modern alluviums. Among the new 

 facts contained in a memoir published by Eenevier, on the appearance 

 of this chart, we mention the discovery of a tooth of Otoduk in the sand- 

 stone of Taveynnaz. This is the first time a fossil has been observed in 

 this rock. {Archives, 1867, t. 59.) 



Professor A. Favre has given some explanations of the geological, 

 chart of the canton of Geneva, scale 25 ooo' ^"^^ submitted them to the 

 society. The various strata which compose this region have been 

 already described elsewhere. The most ancient rock is the sandstone, 

 which is divided into the red, or lower, sandstone, and the gray sand- 

 stone, containing traces of lignite and gypsum. 



The ancient alluvium rests upon the sandstone, and appears at vari- 

 ous levels ; it is composed, at its base, of clay without pebbles, and with 

 lignite surmounted with a formation of worn pebbles and sand, often 

 in a state of hard conglomeration. M. Favre has recently discovered in it 

 scratched pebbles and insertions of a rock of a glacial character. {Bulle- 

 tin Soc. geol. de France, 1875, iii, t. 723, and Archives, 1877, 58, p. 18). If 

 such observation are multiplied they will probably acquire such impor- 

 tance that a refutation may be deduced from them of the hypothesis of 

 two glacial periods. The glacial stratum resting upon the ancient allu- 

 vium is composed of clay more or less gravelly ; it constitutes the 

 largest part of the surface of the canton. Erratic blocks are found upon 

 it, all from the valley of tlie Rhone, while there appear to be none from 

 the valley of the Arve. 



The post glacial alluviums are composed of gravel and of sand from ter- 

 races more or less elevated upon the borders of the lake and of the 

 rivers. They contain many pebbles, broken and indented. This de- 

 struction or decomposition of pebbles, near the surface of the soil, is 

 without doubt one of the principal causes of the formation of vegetable 

 earth. We find in the canton much sandy soil, fine sand, and small 

 gravel. These are of different ages, and formed of various rocks. 

 Particles of oxidized iron are found in tbem, which attest their Alpine 

 origin. Peat and marshy ground are not of frequent occurrence in the 

 canton. M. E. Favre has presented Some rcmarJcs upon the origin of an- 

 cient alluvium. He has indicated the principal characteristics, and has 

 especially dwelt upon the sections of the Bois de la Batie and the quarry 

 of Mategnin. He concludes that the formation of this stratum, entirely 

 composed of worn pebbles, was intimately connected with the extension 

 of ancient glaciers, and that its presence at various levels on the sides 

 of the mountains and in the bottoms of the valleys is because the ice 

 covered very uneven ground. {Archives, 1877, t. 58.) 



M. de Loriol has exhibited two species of EchinoMs from Maurice Isl- 



