508 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 24, 



regularly and horizontally, which holes are seen at the height of 

 about 9 metres above the sea-level. 



Along the shore from Aci Trezza to Capo de' Molini we may con- 

 tinually observe, at the height of from 3 to 5 metres, large blocks of 

 prismatic lava and basalt, rolled and blunted, the calcareo-siliceous 

 shelly deposit, and marine breccia, formed of pebbles (ciottoli) of 

 augitic lava, of basalt, and sandstone, and of gasteropodous and lamel- 

 libranchiate shells. 



From this place to Aci Reale, the recent volcanic currents do not 

 present any phenomena of interest. On the shore of the cliff of the 

 Scalazza of Aci Reale, we find large blocks of compact augitic lava 

 more or less rolled and rounded, which have generally the surface 

 corroded by the action of chloride of sodium and other salts of the 

 sea-water. We likewise find in this place, among the blocks, the 

 calcareo-siliceous deposit, which extends upon them from 2 to 4 

 metres in height ; and the immense current, which forms the wonder- 

 ful Grotto delle Colombe, shows a zone of erosion several metres in 

 height. 



The shore of S. Tecla is almost entirely formed of recent alluvium, 

 the materials of which are pebbles of felspathic and augitic lava of 

 various sizes. Then come volcanic (augitic) currents from Etna, more 

 or less recent ; and lastly, from Prajola to the Onobola a great allu- 

 vial deposit extends along the shore. 



Now from these observations we may discern — 

 1st. That from the shores of the Simeto to the Onobola we find 

 from place to place undeniable characters of the ancient levels of the 

 sea in the recent epoch. 



2nd. That the great blocks with blunted angles, rolled, and cor- 

 roded on the surface, the calcareo-siliceous shelly deposit, and the 

 marine breccia, which are seen at different heights above the level of 

 the sea, are the effect of the continued and daily action of the waves 

 of the sea. 



3rd. That the existence and disposition of the holes of the Modiola 

 lithophaga, Lamk., in the calcareo-siliceous shelly deposit, and the 

 normal position of the shells, both gasteropod and lamellibranchiate, 

 make one suppose a slow and gradual elevation of the coast. 



4th. Lastly, that the Lithophagce and the calcareo-siliceous deposit 

 being found on several islands and on the Faraglione of the Birds up to 

 the height of almost 13 metres, and on the shore of the Pietra degli 

 Uccelli there being large blocks of lava, blunted, rolled, and invested 

 with Serpulce to the height of 14 metres, we may establish the mean 

 height to be 13 metres and 5 decimetres, — the greatest height of the 

 now undeniable gradual elevation of the coast of Sicily from the 

 Simeto to the Onobola during the present period. 



