396 
THE GEOLOGIST. 
formation was observed by de Saussure* ia the Straights of Messina ; 
and M. de Boblayef has described a similar rock which he found on the 
coast of Australia. Fiuallj', 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 Cauary 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 metaiuorphism 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 scries of investigations already made on metamorphism. 
Metamorphic phcno;aena 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 chepaical 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, kc, the author 
has been led to conclude that the four elementary bodies, carbon, 
chloiiue, 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 
" Voyaz/e dans les Alpes. — T. L. P. 
t And likewise Perron (see Beudant, Geologic). — T. L. P. 
} See the Geologist for February, 1858, p. 72 et say.— T. L. P. 
[] Topaz contains mica, &c. — T. L. P. 
