128 THEORY OF THE EARTH. 



had been built by the Greeks at the edge of the 

 sea ; yet in Strabo's time it was ninety stadia 

 from it, and is now destroyed. Adria in Lom- 

 bardy, which gave name to the Adriatic sea, and 

 of which it was, somewhat more than twenty cen- 

 turies ago, the principal port, is now six leagues 

 distant from it. Fortis has even rendered it pro- 

 bable that, at a more remote period, the Euga- 

 nian Mountains may have been islands. 



M. de Prony, a learned member of the Insti- 

 tute, and inspector- general of bridges and roads, 

 has communicated to me some observations which 

 are of the greatest importance s as explaining those 

 changes that have taken place along the shores of 

 the Adriatic *. Having been directed by govern- 

 ment to investigate the remedies that might be ap- 

 plied to the devastations occasioned by the floods 

 of the Po, he ascertained that this river, since the 

 period when it was shut in by dikes, has so great- 

 ly raised the level of its bottom, that the surface 

 of its waters is now higher than the roofs of the 

 houses in Ferrara. At the same time, its allu- 

 vial depositions have advanced so rapidly into tire 

 sea, that, by comparing old charts with the pre- 

 sent state, the shore is found to have gained more 

 than six thousand fathoms since 1604, giving an 

 average of a hundred and fifty or a hundred and 



Note M. 



