THEORY OF THE EARTH. 183 



Thirdly, The extremities of the promontories 

 formed by the two principal branches of the Po, 

 before the excavation of the Taglio di Porto Viro, 

 had extended by the year 1600, or in four hundred 

 years, to a medium distance of 18,500 metres* be- 

 yond Adria; giving, from the year 1200, an ave- 

 rage yearly increase of the alluvial land of 25 

 metres.^ 



Fourthly, That the extreme point of the present 

 single promontory, formed by the alluvions of the 

 existing branches, is advanced to between thirty- 

 two and thirty-three thousand metres^ beyond 

 Adria; whence the average yearly progress is 

 about seventy metres^ during the last two hundred 

 years, being greatly more rapid in proportion than 

 in former times. 



* Or 20,231 yards. Transl. 



f Exactly 27 yards 1 foot and l-4th of an inch English. Transl. 



\. Already stated at from 19 3-4 to 20 1-2 miles; or more precise- 

 ly, from 34,995 yards 1 foot 8 inches, to 36,089 yards 10 inches Eng- 

 lish measure. TransL 



^ Equal to 76 yards 1 foot 7 inches and 9-loth- 



