PREFACE. 



limestone, in which the casts and impressions of shells 

 alone were discernible, vanished at once from my 

 mind. At the same time, I was struck with the iden- 

 tity of the associated igneous rocks of the Val di Noto 

 with well known varieties of e trap ' in Scotland and 

 other parts of Europe, varieties, which I had also 

 seen entering largely into the structure of Etna. I 

 occasionally amused myself with speculating on the 

 different rate of progress which Geology might have 

 made, had it been first cultivated with success at 

 Catania, where the phenomena above alluded -to, and 

 the great elevation of the modern tertiary beds in 

 the Val di Noto, and the changes produced in the 

 historical era by the Calabrian earthquakes, would 

 have been familiarly known. 



From Cape Passaro I passed on by Spaccaforno and 

 Licata to Girgenti, where I abandoned my design of ex- 

 ploring the western part of Sicily, that I might return 

 again to the Val di Noto and the neighbourhood of 

 Etna, and verify the discoveries which I had made. 

 With this view I travelled by Caltanisetta, Piazza, 

 Caltagirone, Vizzini, Militello, Palagonia, Lago Naftia, 

 and Radusa, to Castrogiovanni, and from thence to 

 Palermo, at which last place I procured the shells 

 named in Appendix II. p. 55. The sections on this 

 new route confirmed me in my first opinions respecting 

 the Val di Noto, as will appear by the 6th, 8th, and 

 9th chapters of the third Volume. 



When I again reached Naples, in January, 1829, I 



