120 PROCEEDESTGS OF THE GEOLOGICAL SOCIETY. [JuHG 23, 



(fig. 3) is somewhat towards the valley ; but I believed it to be much 

 more so on the north-western top of the steep border of the Yal di 

 Bove on the side of Schiena dell'Asino. I observe too that the dip 

 of the beds of the said Schiena was at 16° to 20° towards the N.N.E., 

 and prevailed throughout the whole ridge as far as the Cirrita. I 

 saw the conformity of stratification away from the valley, with the 

 same dip of the beds of Schiena dell'Asino, in the Eocca deUa 

 Capre and Musarra (fig. 2 ) ; and all seemed to me, according to 

 my theoretical view, quite right, when I found on the side of 

 Zoccolaro, notwithstanding great irregularities, a mean inclination 

 of all the beds towards south and south-east. According to my 

 view I believe it impossible that the effect of a subsidence of so 

 enormous extent as that corresponding to the circuit of the actual 

 Val di Bove should have taken place without the greatest derange- 

 ment, especially in the original structure of the central masses of 

 the mountain (fig. 4 h, c, d), by a gliding towards the chasm in an 

 altered position between h and a, fig. 1. 



The considerable anomaly in the dip of beds away from the valley 

 round or behind the Giannicola, I looked upon as a natural conse- 

 quence of the protrusion of that gigantic dyke, or rather system of 

 dykes, constituting the Solfizio and the Giannicola. When descending 

 from the border of the Piano del Lago (fig. 4 a), and studying step 

 by step the stratified masses, I was struck by the relation I saw 

 between the beds (originally horizontal) dipping away from the 

 vaUey and the protrusion of the immense dykes, the direction of 

 which, as far as my examination could reach, was that of N.N.W.- 

 S.S.E. This circumstance strengthened me in the opinion that this 

 anomalous position of the beds ought to be a consequence of the 

 protrusion of the dykes almost perpendicular to the chief direction 

 or great axis of the elliptical chasm of the Yal di Bove. When 



Fig. 5. — View of Montagnuola. 



a. " Lava tavolata " of the same mineralogical composition as those beds be- 

 longing to uppermost lava-currents of the Piano del Lago, the same which make 

 their appearance in the interior of the Cisterella, where I observed 15 beds super- 

 posed one on the other. 



b. Lava of the eruption of Montagnuola. 



c. Cone of eruption ; ejected cinders and capilli. 



\a is to c as Somma {cratere de soulevemenf) is to Vesuvius {volcan).'] 



studying the remarkable Montagnuola, on the southern extremity 

 of that part of the edge of the valley which stretches from N. to S., 



