ef Serpentine, Sfc. in the Apennines. 165 



These two rocks differ but little from each other. 



c. A very fine grained compact limestone, easy to break, 

 with a conchoidal fracture, sometimes a little scaly ; of an 

 ash or bluish grey colour, with veins of calcareous spar. 



(At Rochetta de la Spezia j at Doccia near Florence ; at 

 Pietramala, &c.) 



. d. A marly schist, sometimes rather solid, but extremely 

 fissile and dividing in the manner of slates (between Bari- 

 gazzo and the Col of Bosco-Lungo, road from Modena to 

 Pistoia), sometimes of a yellowish brown colour, of a dull 

 and even earthy aspect, and resembling marl ; often even so 

 fissile and disunited, that it is impossible to obtain a speci- 

 men fit for shewing its characters. (At Rochetta de la 

 Spezia, on the borders of Cravignola). This schist passes 

 into a dull argillaceous slate containing a little mica, into 

 spangled (paillete) argillaceous slate containing more mica, 

 w ithout from this circumstance ceasing to be marly, that is, 

 ceasing to effervesce with nitric acid ; in this respect very 

 different from ancient argillaceous schist, which is dull, and 

 does not contain lime. 



Such are the rocks of a calcareous, arenaceous, and schist- 

 ose nature that occur most abundantly in those parts of the 

 Apeninnes I have pientioned. They alternate with each 

 other without any order, often many times in a short space; 

 they pass into each other by insensible gradations ; they 

 form entire and very elevated mountains, chains of hills 

 and mountains of great extent, and offer some peculiarities 

 in their structure, which I shall make known when I 

 describe the places where I have observed the positions that 

 constitute the principal object of this memoir. 



2. The ophiolitic or serpentine formation is composed, 

 in these same districts, of the following rocks, forming its 

 principal and essential parts. 



a. Asbestiferous greenish serpentine, brown serpentine 

 with diallage, and common serpentine. 



Throughout the whole valley of the Magra, and the Vara ; 

 in the environs of Prato, on the north of Florence; on the 

 south, at Imprunetta ; near Pietra-mala, on the road from 

 Florence to Bologna ; to the north of Genoa, at Mout 



