Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/633

FUCHS—MOLLUSCA OF THE UPPER TERTIARIES. 9 On the Lavas of Vesuvius. By Professor Fuchs. [Proceed. Nat. Hist, and Med. Soc. Heidelberg, January 22, 1869.]

The author states that the chemical composition of the Vesuvian lavas is nearly the same from the oldest to the most recent. Soda is the only very variable constituent; it ranges from 1-1/2 to 5 per cent. This variation is due to secondary chemical processes taking place before the outpouring of the lava. The three most essential mineral constituents are leuzite, augite, and magnetic iron. With these are associated; but often only in small quantities or in particular lavas, olivine, mica, hornblende, garnet, sodalith, felspar (triclinic and sanidine), nepheline, and apatite. Only a small portion of the leuzite is in well-developed crystals, an indication that after its formation it was partially altered by the high temperature of the surrounding lava mass. Similar alterations appear to have been produced in a great part of the constituent minerals of the lava. The lava, containing both crystalline and amorphous mineral substances, must have consisted at the time of its outflow of a fused mass in which crystals and fragments of crystals swam. The author has repeated and extended the investigations of Forchhammer and Rogers upon the action of hot water under strong pressure upon the silicates of which the lava is composed. This action is particularly energetic when the water contains carbonic, hydrosulphuric, sulphurous, or hydrochloric acid; and it is to it that the author attributes the changes produced in the chemical constitution of the lava. [W. S. D.]

Mollusca of the Upper Tertiaries of the Vicentine. By Herr T. Fuchs.

[Proceed. Imp. Acad. Vienna, July 23, 1868.]

The whole number of species recorded by the author is 214 (among which 71 are new), distributed as follows through the stratigraphical subdivisions:—Castel' Gomberto strata 118, Laverda strata 12, Sangonini strata 119. Of these 214 species, 128 are known to occur in other localities, viz. 70 in the Inferior Eocene (Sables inferieurs, Calcaire grossier, Sables moyens, Barton Clay, and their equivalents), 91 in the Upper Eocene (Oligocene). Only 24 species are common to the upper and inferior Vicentine Tertiaries, from which last about 300 species are known, so that the limit between the upper and inferior deposits is far more distinctly traced than it is, for example, in the Hampshire basin, where, according to Prof, von Koenen, 22 species, identical with those of the Barton Clay, are met with among the 54 species of the Oligocene Fauna of Brockenhurst. There is not one single species among the 300 just mentioned which is, at present, known to occur exclusively in the Upper Eocenes. No trace is found at Ronca of the comparatively far more recent species erroneously ascribed to this locality, but in reality imbedded in Castel' Gomberto strata or in the basaltic tuffs of Sangonini, while Ronca offers many new forms associated with a surprising abundance of beautiful Calcaire grossier forms. In consequence, the