114 RAMBLES OF A NATURALIST. 



strong inclination downwards, near the Porta di 

 Callana, one of the eastern outlets of the Val del 

 Bove. At some points this inclination amounts to 

 as much as twenty-nine or thirty degrees. 



If the lava of which they are formed had flowed 

 over surfaces so much inclined as these, they must 

 necessarily have presented considerable variations 

 both in their mode of aggregation and in their thick- 

 ness ; but, as we have already observed, these strata 

 are perfectly regular and parallel at all parts. All 

 these strata rise and fall together, as the leaves of a 

 book would do, if the whole were folded over one 

 another in the same direction. We are, therefore, 

 led to admit that at the epoch of their formation the 

 soil presented a very different configuration from that 

 which we now observe. 



This conclusion derives confirmation from a still 

 more striking fact. The walls of the Val del Bove 

 are not formed exclusively of those long strata of 

 which we have spoken, for an immense number of 

 veins or lodes, of variable diameter, intersect them 

 from below upwards at very different angles. These 

 veins are composed of the same rock as the strata, 

 and many of them, by intermingling with and follow- 

 ing the direction of the latter, clearly show their real 

 nature. It is evident that they are fissures through 

 which the lava formerly escaped, and which have re- 

 mained filled with the same substances which were 

 ejected from them. 



On examining one of these veins, abutting upon a 

 lava bed on the middle of even a somewhat steep de- 

 clivity, we find that the stream, without presenting 



