^96 THE GEOLOGIST. , 



formation was obseryed by de Saussure^^* in the Straights of MessinM 

 and M. de Boblayef has described a similar rock which he found on the 

 coast of Australia. Finally, deposits of marine tufa have been noticed 

 in recent times at certain points of the English coast. 



Whilst noticing rocks of modern formation, we should bear in mind 

 the curious Oolitic limestone deposit which is being effected at the 

 present time in the great lakes of Mexico, and the modern Oolite dis- 

 covered by Leop. von Buch, in the Canary Islands. J 



M. Ch. Sainte Claire Deville, recently elected member of the Academy 

 of Sciences, at Paris, has just read before that institution a long memoir 

 on the action of the chlorides and sulphates of alkalies and earths in 

 the metamorphism of sedimentary strata. Following in the path 

 trodden by Sir James Hall, Dulong, Haidinger, Marignac, Daubree, 

 and others, the author has added one or two new features to the in- 

 teresting series of investigations already made on metamorphism. 

 Metamorphic phenoraena have been so frequent on the surface of the 

 globe, that although rocks may have been wonderfully changed by it in 

 aspect and chemical composition, the processes by which these changes 

 have been produced must nevertheless, thinks M. Ch. Deville, have been 

 characterized by a certain simplicity ; the chemical re-actions, of which 

 we see the results, must have taken place between bodies which are 

 abundant in the crust of the earth. By his researches on the gaseous 

 emanations observed in volcanos, salzes, hot-springs, &c., the author 

 has been led to conclude that the four elementary bodies, carbon, 

 chlorine, sulphur, and fluorine, predominate in the chemical phenomena 

 of the globe ; and that they or their compounds must have played a 

 great part in the metamorphism of rocks. From their action on sedi- 

 mentary strata, says he, have arisen — 1st, insoluble substances, as the 

 minerals observed to have been formed in strata which have undergone 

 metamorphism, and in which the carbon is seen to have been almost 

 wholly fixed in the state of carbonates, the sulphur mostly as sulphates 

 and sulphides, some traces of chlorine only, as chlorides, and nearly 

 the whole of the fluorine, as fluor-spar, and certain fluo-salts ; || 2nd, 

 soluble salts, containing nearly the whole of the chlorine, a good deal 



Voyage dans les Alpes. — T. L. P. 

 t And like-wise Perron (see Beudant, Geologic). — T. L. P. 

 X See the Geologist for February, 1858, p. 72 et say.— T. L. P. 

 11 Topaz contains mica, &c. — T. L. P. 



