414 dN THE ALLUVIUM OF THE PO. 



Towards the middle of the twelfth century, the flood- 

 waters of the Po were retained on their left or northern 

 side by dikes near the small city of Ficarolo, which is 

 about 19,000 metres* to the north-west of Ferrara, 

 spreading themselves southwards over the northern part of 

 the territory of Ferrara and the Polesine of Rovigo, and 

 flowed through the two formerly mentioned canals of 

 Mazzorno and Toi. It seems perfectly ascertained, that 

 this change in the direction of the waters of the Po had 

 been produced by the effects of human labours ; and the 

 historians who have recorded this remarkable fact only 

 differ from each other in some of the more minute de- 

 tails. The tendency of the river to flow in the new chan- 

 nels, which had been opened for the more ready dis- 

 charge of its waters when in flood, continually increased; 

 owing to which the two ancient chief branches, the Vola- 

 no and Primaro, rapidly decreased, and were reduced in 

 less than a century to their present comparatively insig- 

 nificant size ; while the main direction of the river was 

 established between the mouth of the Adige to the north, 

 and what is now called Porto di Goro, on the south. 

 The two before-mentioned canals of Mazzorno and Toi 

 becoming insufficient for the discharge, others were dug; 

 and the principal mouth, called Bocco Tramontana, or 

 the northern mouth, having approached the mouth of 

 the Adige, the Venetians became alarmed in 1604 ; when 

 they excavated a new canal of discharge, named Taglio 

 de Porto Viro, or Po delle Fornaci, by which means the 

 Bocco Maestro, was diverted from the Adige towards the 

 south. 



Or 20,778 yards 1 foot 10 inches Transl 



