and the Phenomena accompanying their Elevation, 17 



cumulations of diluvium are seen, which have exactly the same 

 characters everywhere as far as the plain of Catania. They al- 

 ways occupy the bottom of the valleys, have frequently a depth 

 of from fifty to sixty feet, or even more, and, having been cut 

 through by the rivers, form steep escarpments along their sides. 

 They consist of rolled pebbles of the old sandstone, of the ter- 

 tiary conglomerate and limestone, and of a great deposit of grey 

 clay, which not only connects the pebbles, but rises above them 

 \Q a. great thickness, containing sometimes great numbers of 

 helices and cyclostomae, asssociated in one instance, near Castro 

 Giovanni, widi lymneae. In some places, a diluvium of a dif- 

 ferent and older date from this may be observed, rising to very 

 considerable heights, on the sides or summits of the hills. It 

 consists of larger rolled fragments of sandstone, with a few frag- 

 ments of the tertiary rocks, connected by a sandy clay, and no- 

 where accompanied with the great deposit of grey clay which 

 forms the principal feature of the other. 



The two diluvia (terrains de transport, Fr.) may be well 

 seen in the valley of the Simethus. There, the new diluvium 

 forms a perfectly level plain, with a height of probably twenty 

 or thirty feet above the river, and has exactly the same charac- 

 ters which I have already described, with the exception, that it 

 contains a few fragments of granite, and numerous rolled masses 

 of at least two kinds of cellular lava. 



This plain is bordered on its eastern side by a steep bank of 

 about forty or fifty feet in height, which also supports a plain 

 extending as far as the surrounding hills. At a distance I sup- 

 posed that this horizontal deposite, with its bare rocky front, 

 might be a recurrence of the tertiary beds; but upon approach- 

 ing it, I found it to consist of a coarse conglomerate, containing 

 large and small rounded masses of the older and of the tertiary 

 rocks, firmly united by a calcareous cement. The most com- 

 mon fragments were of the old sandstone, of the tertiary con- 

 glomerate and hmestone, in one of which I found tertiary shells, 

 with a ^evf of granite, gneiss, red porphyry, and basaltic lava con- 

 taining olivine. This diluvium also covers the sides and sum- 

 mits of most of the rounded undulating hills between Palermo 

 and Cataniaj where I observed it at the height of about 800 feet 

 above the sea. It contains the same fragments as those already 



OCTOBER DECEMBER 1831. B 



