These, however, are, in a few years, filled up by 

 the operations of rains upon the surrounding new made 

 grounds, and that of the winds, which, in dry seasons, 

 elevate the dust and soil in clouds, from high and ex- 

 posed situations, and deposite them in those which arc 

 tranquil and low. 



Thus the progressive work is continued through 

 succeeding ages, deriving its materials from the sources 

 which I have described, and forming new districts be- 

 yond the ancient limits of the ocean, for the improve- 

 ment, cultivation, and residence of man. 



To these causes we may look, for the formation of 

 the delta of the Po, in support of which, 1 shall offer 

 some of the remarks of M. de Prony. 



In speaking of the great canal, denominated Taglio 

 di Porto Viro, or Podelle Fornaci, he observes : " In 

 proportion as their entrances into the sea extend from 

 the original land, the yearly quantity of alluvial depo- 

 sitions increases in an alarming degree, owing to the 

 diminished slope of the streams, which was a necessary 

 consequence of the prolongation of their bed, to the 

 confinement of the waters between dykes, and to the 

 facility with which the increased cultivation of the 

 ground enabled the mountain torrents which flowed 

 into them to carry away the soil.* 



Here the increased cultivation of the grounds, which 

 enabled the mountain torrents to carry away the soil, 

 is considered as the principal source of the alluviou, 



* See Cuvier's Iheorj, Aaiericao edition, p. 181. 



