84 ON THE REVOLUTIONS OF 



the annual quantity of deposites increase in an alarming degree, as 

 well from the diminution of the inclination of the waters (the neces- 

 sary consequence of the extent of the bed of the river) as from the 

 confinement of these waters within dykes, and by the facilities which 

 the recently cultivated sloping lands afforded of carrying the soil of 

 the mountains into the plains. Thus the bay of Sacca di Goro was 

 choked up, and the two promontories formed by the two first mouths 

 united into one, the present extremity of which is thirty-two or thirty- 

 three thousand metres (nineteen to twenty miles) from the meridian of 

 Adria. Thus, in two centuries, the mouths of the Po have gained 

 fourteen thousand metres (nearly nine miles) on the sea. 



" Of this hasty sketch these are the results : — 



" 1st. That at an early period, the precise date of which cannot be 

 ascertained, the Adriatic Sea washed the walls of Adria. 



" 2ndly. That in the twelfth century, before a passage had been 

 opened at Ficarolo, for the waters of the Po, on the left bank, the sea 

 shore was removed nine or ten thousand metres (six miles) from 

 Adria. 



"3dly. That the extremities of the promontories formed by the 

 two principal mouths of the Po, were, in 1600, before the formation 

 of the canal of Taglio di Porto Viro, at a mean distance of eighteen 

 thousand five hundred metres (twelve miles) from Adria ; which, since 

 the year 1200, gives an extent of alluvial deposite of twenty-five me- 

 tres (twenty-seven yards one foot and a fraction, English admeasure- 

 ment*). 



" 4thly. That the extremity of the single promontory, formed by 

 the present mouths, is thirty-two or thirty-three thousand metres 

 (nineteen to twenty miles) from the meridian of Adria ; whence we 

 may conclude the mean progress of the alluvial deposites to be about 

 seventy metres (upwards of seventy-six yards) per annum for the last 

 two centuries, which is a rapidity greater than that of preceding ages. 



" De Pkony." 



M. de Prony having been employed by the government to examine 

 what remedies could be applied to the devastations occasioned by the 

 floods of the Po, ascertained that this river, since the time when dykes 

 inclosed it, had elevated its bed so greatly, that the surface of its waters 

 is now higher than the roofs of the houses of Ferrara ; at the same 

 time, its alluvial deposites have advanced to the sea with so much 

 rapidity, that, on a comparison between the ancient charts and the 



* The metre was a measure adopted during the French revolution of about 39j 

 inches, Euglish measure. — Translator. 



