58 



Sdly. That occasioned directly or indirectly, by 

 the labours of man. 



Under these circumstances I shall proceed to exa- 

 mine the delta of the Po, a case as interesting in its 

 kind, as that of almost any other, and on which much 

 has been said, to prove that it is, almost exclusively, 

 the result of the alluvion brought down by the current 

 of that river, and deposited at its mouth. 



In order to determine the quantity and extent of the 

 alluvion, naturally formed by this river, it is necessa- 

 ry to ascertain, as near as possible, what were the si- 

 tuation, and appearances at its mouth and in its vici- 

 nity, when first known, and before the settlement and 

 cultivation of the surrounding country. 



This it is difficult, nay impossible :, to determine with 

 any degree of accuracy : we have, however, a datum 

 afforded, which will enable us to form an opinion, suf- 

 ficiently correct for our present purpose. It is that 

 which relates to the city of Hatria, now Adria. 



M. de Prony, in his researches on the Hydraulick 

 system of Italy, observes, We are, however, certain, 

 that the city of Hatria, now called Adria, was former- 

 ly situated on the edge of the coast ; and by this we at- 

 tain a known fixed point upon the primitive shore, 

 whence the nearest part of the present coast, at the 

 Adige, is at the distance of 20,000 metres."* 



* Equal to 27.340 yards and 10 inches English measure, or fif- 

 teen and a half miles, and sixty yards. 



