261 



of Adria, the shore of the Adriatic had heen removed 

 to the distance of about ten thousand metres* from it. 



This intrusion of the delta, will give an annual 

 average increase of ahout ten feet and a half. 



But it must he recollected; that the increase of the 

 alluvial formation, at first, was scarcely perceptible; 

 and that its subsequent extension was almost in a geo- 

 metrical proportion ; so that the gain of the last five 

 hundred years, must have been, perhaps, nearly equal 

 to the whole gain during the preceding period, as will 

 appear in the sequel. 



Let us now examine the rapid increase of the delta 

 at the Po, from the end of the twelfth century to that 

 of the sixteenth, and so on, to see the proportion which 

 the gain of the latter hears to the former, in order to 

 determine whether it has heen produced by the allu- 

 vion brought down by the current of the river. 



61 During four centuries," says M. de Prony, " from 

 the end of the twelfth to that of the sixteenth, the al- 

 luvial formation of the Po gained considerably upon 

 the sea." 



The northern mouth, which had usurped the situa- 

 tion of the Mazzarno canal, becoming the Ramo di 

 Tramontana, had advanced in the year 1600, to the 

 distance of twenty thousand metresf from the meridian 

 of Adria; and the southern mouth, which had taken 



* Equal to ten thousand nine hundred thirty-six yards, or six 

 miles and three hundred sixty-four yards. 



t Equal to twenty-one thousand eight hundred seventy -two 

 yards. 



