4^ M. Von Buch on Gabbro. 



VivianI observed it in 1806, and described it in tlie Journal 

 de Physique. Its mass is composed of white felspar and 

 jade ; diallage occurs in blackish green fragments, of a very 

 laminated texture, possessing a metallic lustre. Dr. Viviani 

 has observed the relations that exist between serpentine and 

 gabbro, which he proposes to name serpentine gianite. M. 

 von Buch had found it in another part of the same moun- 

 tains in 1799, where the rocks become more ancient, as they 

 recede from the sea. Quitting Spezzia'a fine grained grey- 

 wacke is first observed, then a red and black transition 

 limestone ; nothing but gabbro is met with from Borghetto 

 to Matanara. Near Sestri it is covered by schist worked as 

 roofing slate at Lavagna and Chiavari. Lastly, Saussure 

 mentions (§ 1362) a species of granite composed of white 

 jade, a little granulated, and of laminated grey diallage 

 (smaragdite) which he found near the castle of Inerca, in 

 the Riviera de Ponenta, succeeding suddenly to the serpen- 

 tine and other talcose rocks, which cover mica slate near 

 Voltri.* 



♦ M. von Buch observes that the primitive rocks of this country are 

 exposed to view on the sea coast only, near Voltri, at Savona, and at 

 Cape Nolis ; but that no more traces of them are observable, either to- 

 wards Nice, or in the interior of the country, in the direction of the great 

 mountains of Piedmont. The opinion of those then, he adds, is erroneous, 

 who judging only from geographical maps, make the Corsican mountains 

 a continuation of those of the environs of Genoa; they unite things that 

 are entirely different. It would be as extraordinary to affirm that Cape 

 Corte, formed of granite, is a continuation of Cape Delia Melle, composed 

 of black transition limestone, as it would be to affirm that the Voso'es is 

 a continuation of the Jura. 



We shall remark, upon this head, that a similar error is committed 

 every day by those who make maps, and by those, who, reasoning from 

 them believe that the mountains of Hunsdruck and Eiffel, on the left bank 

 of the Riiine, are the continuation of the Vosges. The chain of the Vosges, 

 with a direction from south to north, formed almost exclusively of sand- 

 stone from the latitude of Strasburg, and diminishing in height in its 

 northern parts, finishes a few leagues south of Mont Tonnere, in the hills 

 and plains of the Palatinat. The schistose mountains of Hunsdriick, on 

 the contrary, unite themselves with those of the same nature of the 

 Ardennes, and form a chain, having a direction from S.W. to N. E., 

 separated from the Palatinat" by the porphyries of Mont Tonnere, of 

 Greutznach, &c. and by the trap formation of the banks of the Nahe. 



