206 M. BnoxGNiART on the position 



Plate VI. 



Fig. 1. 2. 3. Disposition of the serpentines, compact 

 limestone, and dull micaceous argillaceous slate, observed 

 at different points going from Poggio del Gabbro at the S. 

 of Volterra, at the Lagonis of Monte Cerboli. 



These sections are theoretical, i. e. that they are not 

 the exact representation of the rocks observed, but only 

 the graphic indication of the disposition of the rocks, such 

 as it appears ought to result from the points observed at 

 different distances, brought nearer in the figure, and 

 placed in the relations which it is thought may be recog- 

 nised between these different rocks. 



Fig. 1. Hill named Poggio del Gabbro. 

 C. Fragments of jasper on the northern side of the 

 hill. 



D & E. Smoke grey compact limestone and marly 

 schist, dipping beneath the serpentine A. 



G. Gypsum which apparenly rests on the serpentine. 

 H. Clay alternating with the gypsum. 

 P. Siliceous conglomerate in an unconformable po- 

 sition. 



Fig. 2. Descent towards the village of Monte-Cerboli. 

 B. Ill determined serpentine, mixed with diallage 

 rock. 



D & E. Smoke grey compact limestone, dipping be- 

 neath the rocks. 



Fig. 3. Graphic indication of the disposition of the 

 Lagonis, and the aqueous vapours in the valley at the foot 

 of the hill of Monte-Cerboll. 



D. Smoke grey compact limestone, &c. in highly in- 

 clined and much broken beds, in the southern portion, 

 leading to Castel-Nuovo. 



d. Indication of the debris and fallen calcareous masses 

 towards the valley of the Lagonis. 



M. A mass without structure of soft clay, of marly 

 schist, of calcareous blocks and fragments, composingthe 

 bottom of the depression in the form of a basin, from which 

 aqueous and sulphureous vapours rise up with violence. 



