THE COASTS OF SICILY. 113 



which appear to be in flagrant contradiction to the 

 laws to which we have just referred. The interior 

 escarpments of the valley are composed of several 

 hundred strata, which are alternately formed by 

 ledges of rocks and beds of fragmentary or pulveru- 

 lent materials. These substances, which are very 

 nearly similar at first sight to the lava of the present 

 geological epoch, exhibit nevertheless a general 

 tinge of grey, to which the deep black colour of the 

 modern streams presents a strong contrast. They 

 are moreover, like the latter, igneous rocks and true 

 lava. All these strata are perfectly regular, and 

 from one extremity of the valley to the other, that 

 is to say, for about a length of six miles, their borders 

 present the most perfect parallelism, without enlarge- 

 ment or constriction. 



To explain this result, we must necessarily admit 

 that, in issuing from the earth in a liquid state, these 

 lava streams have flowed over a plane and nearly 

 horizontal surface, where they could slowly cool and 

 solidify. But yet, at the present day, their strata ex- 

 hibit determined inclinations ; and on the borders of 

 the Piano del Lagothey begin to dip, burying them- 

 selves under the tuflfa of Etna, not far from the village 

 of Milo. Moreover, in this long course they present 

 various undulations and very great differences of in- 

 clination. At the Rocca del Solfizio they are almost 

 horizontal; but below the Montagnuola, they assume 

 an inclination of seventeen degrees. They again ap- 

 proach the horizontal line under the flanks of Mount 

 Zoccolaro, which forms the southern enclosure of the 

 valley ; and then, after curving suddenly, they take a 



VOL. II. I 



