162 



DELTA OF THE PO. 



son he ascribed a certain bituminous, saline, and glu- 

 tinous nature to the substances brought down with 

 sand by the Rhone. If the number of mineral 

 springs charged with carbonate of lime, which fall 

 into the Rhone and its feeders in different parts of 

 France, be considered, we shall feel no surprise at 

 the lapidiflcation of the newly-deposited sediment 

 in this delta." 



Delta of the Po. — The Po and the Adige are the 

 principal streams which drain, on the one side, a 

 great crescent of the Alps, and, on the other, some 

 of the loftiest ridges of the Apennines. From the 

 northernmost point of the Gulf of Trieste down to 

 the south of Ravenna, there is an uninterrupted se- 

 ries of recent accessions of land, more than 100 

 miles in length, which, within the last 2000 years, 

 have increased from two to twenty miles in breadth* 

 The town of Adria, which was a seaport in the 

 time of Augustus, and in ancient times gave its 

 name to the gulf, is now about twenty miles in- 

 land. Ravenna was also a seaport, but is now four 

 miles from the sea. Spina, a very ancient city, 

 originally built on an arm of the Po, on the border 

 of the Adriatic, is now more than twelve miles from 

 the sea. The deposites consist partly of mud and 

 partly of rock, the rock being composed of calcare- 

 ous matter, incrusting shells. Olivi found some 

 deposites of sand, and others of mud, extending 

 half way across the Gulf of Trieste, and states that 

 their distribution along the bottom was determined 

 by the prevailing current. 



Delta of the Nile. — Some of the ancient poets have 

 described Egypt as " the gift of the Nile but, as 

 Lyell remarks, we have no authentic memorials 

 for determining with accuracy the dates of suc- 

 cessive additions made to the habitable surface of 

 that country. Major Rennell, after exploring the 

 country, states that there is no room to doubt that 

 * Brocchi, vol. 1, p. 59. 



