ALTERATIONS OF COAST LINE. 



399 





shore no farther back than the year 1737, being already a French mile from it. At the 

 mouth of the Tibur an increasing delta has, since the classical times, forced the waters 

 three miles back from Ostia ; and the watch-tower of San Michele, built on the sea-side 

 in the middle of the sixteenth century, is already nearly a mile inland. The water which 

 the Tibur receives from the volcanic district around Rome, particularly from the lake of 

 the Solfatara, holds an abundance of carbonate of lime in solution, and precipitates immense 

 quantities of travertin, a circumstance which may contribute to the rapid formation of 

 new land at its mouth. Sir Humphrey Davy placed a stick in this lake, and after an 

 immersion of nearly a year he had some difficulty in breaking with a hammer the mass of 

 travertin which adhered to it, and which was several inches in thickness. Referring to 

 the high temperature of the Solfatara, and to the quantity of carbonic acid it contains, 



favouring vegeta- 

 tion, as well as to 

 its rapid deposition 

 of calcareous mat- 

 ter, he states : 

 " There is, I be- 

 lieve, no place in 

 the world where 

 there is a more 

 striking example of 

 k. the opposition or 

 H^ contrast of the laws 

 f of animate and in- 

 animate nature, of 

 - the forces of inor- 



ganic chemical affinity, and those of the 

 powers of life." 



Along the banks of the Adriatic, for 

 more than a hundred miles, from the 

 1 south of Ravenna to the head of the 



Gulf of Trieste. * gulph of Trieste, the land, receiving 



during the last two thousand years con- 

 stant accessions from the matter carried down by the rivers, as well as from that thrown 

 up by the ocean, has encroached on the sea to a breadth nowhere less than two miles, 

 and in some places amounting to twenty. The Isonzo, Tagliamento, Piave, Brenta, 

 Adige, and Po, drain one side of the Alps and of the Apennines, and carry away a vast 

 quantity of their material, the deposition of which has wrought surprising changes in 

 the outline of the coast. Ravenna, once a sea-port, is now five miles from the water 

 side. In the intervening space, traversed by vessels in ancient times, is the Pineta, or 

 forest of pines, in which Dante, Boccaccio, Dryden, and Byron have wandered, and ren- 

 dered famous.. 



" Sweet hour of twilight ! in the solitude 



Of the pine forest, and the silent shore, 

 Which bounds Ravenna's immemorial wood, 



Rooted where once the Adrian wave flovfd o'er, 

 To where the last Csesarian fortress stood, 



Evergreen forest ! which Boccaccio's lore 

 And Dry den's lay made haunted ground to me, 

 How have I lov'd the twilight hour and thee ! 



