REPORT ON HYDRAULICS. — PART IX. 423 



The Ninfa, which runs into the above, 



inclines from 0*012466 to 0-000090 



Ti,«TTfl? 4^ • V f r 0-000095 0-000049 



The Uffente inclines from 1 0-000410 0-000420 



fist length ....... 0-001751 0-001305 



The Amaseno -^ 2nd ditto 0'000636 0-001152 



[Srd ditto 0*000665 0*000905 



Canal of Botte .... ditto 0*000187. 



Similar examples might be quoted of the Pedicata, the Scara- 

 vazza, &c. 



These inclinations vary according to circumstances, but in 

 general they may be taken from 2WU0 ^o ^oV^- 



M. Prony, in the 8th chapter of his Report, proposes to dis- 

 tribute the inclination of the rivers or drains so as not to 

 corrode their channels ; and this is effected by a series of planes 

 or falls, from 0-0005035 to 0-0002879 ; as an example he cites 

 the marshes of Bourgoin in France *. 



M. Prony proposes to accommodate the high and lovr wa- 

 ters by forming the channel into a double set of trapeziums, 

 so that in times of flood the waters will have liberty to spread 

 above the lower banks ; and being confined between the higher 

 or external banks, the capacity but not the velocity will be in- 

 creased. This is precisely the mode adopted in the Eau Brink 

 and Nene Cuts by the late Mr. Rennie, and by the Italians in 

 the embankment of the Po and other rivers. 



According to Deschalesf, if the depth and quantity of water 

 in a river or canal be considerable, it will suffice in the part 

 nearest the mouth to allow a declivity of one foot perpendicular 

 in from 6000 to 10,000 feet in horizontal extent, above which the 

 declivity must be slowly and gradually increased, as far as the 

 current is made navigable, to 1 foot perpendicular in 4000 feet 

 horizontal. 



Riccioli partly confirms this statement with regard to the 

 mouth of the river Po. The mean declivity of several of the 

 canals and rivers in Flanders was found by the Abbe Mann to be 

 from jaVo ^'^ ^oVo » ^^^ ^^ *^^ I^ys> near Ghent, by M. Brisson, 

 one in ^^qq. According to the observations of the Abb^ Chappe 

 D'Auteroche, M. NoUet and MM. CassiniJ, the height of the 



• Description Hydrographique et Historique des Marais Pontins, &c. : par 

 M. Prony. Paris, 1818, de I'lmprimerie Royale. 

 t De Fontihtis et Fluviis, Prop. 49. 

 X Memoires de VAcademie Royale des Sciences pour 1730. 



