Ch.VIL] 



CYCLOPIAN ISLES. 



81 



No. 16. 



N tf-^.\ ' V ' ' 



be a b 



Newer Pliocene strata invaded by lava^ Isle of Cyclops (^horizontal section). 

 a, Lava. 6, laminated clay and sand, c, the same altered. 



The arenaceous laminae are much hardened at the point of con- 

 tact, and the clays are converted into siliceous schist. In this 

 island the altered rocks assume a honeycombed structure on 

 their weathered surface, singularly contrasted with the smooth 

 and even outline which the same beds present in their usual 

 soft and yielding state. 



The pores of the lava are sometimes coated, or entirely filled, 

 with carbonate of lime, and with a zeolite resembling analcime, 

 which has been called cyclopite. The latter mineral has also 

 been found in small fissures traversing the altered marl,, show- 

 ing that the same cause which introduced the minerals into the 

 cavities of the lava, whether we suppose sublimation or aqueous 

 infiltration, conveyed it also into the open rents of the con- 

 tiguous sedimentary strata. 



Lavas of the Cyclopian Isles not currents from Etna. The 

 phenomena of the Bay of Trezza are very important, for it is 

 evident that the submarine lavas were produced by eruptions 

 on the spot, an inference which follows not only from the pre- 

 sence of dikes and veins, but from those tuffs above Castello 

 d'Aci, which contain angular fragments of hardened marl, evi- 

 dently thrown up, together with the sand and scoriae, by volcanic 



VOL. III. 



G 



