REPORT ON HYDRAULICS. — PART II. 433 



and Romagna, with a view to the regulation of the rivers and 

 the drainage of those districts. Gugliehnini was induded in the 

 Commission on the part of the city of Bologna ; and having in- 

 vestigated the whole of the circumstances connected with the 

 Po and Reno rivers, he published the result of his labours shortly 

 afterwards. In that Report he confines himself to the subject in 

 question, by detailing very fully the various projects which had 

 been proposed to ameliorate the condition of the country and 

 the rivers which flow through it, particularly the Po, the Reno, 

 and the Panaro, and he demonstrates the method by which the 

 difficulties could be overcome. His opinions were questioned 

 by several engineers of that period. In his work entitled La 

 Misura delVAcque Correnti, he adopts the theorems of Castelli 

 and Torricelli, and founds upon them a system of hydraulics in- 

 consistent with experiment, in as much as he makes the velo- 

 city proportional to the square root of the height, and regards 

 every point in a mass of fluid as tending to move with the same 

 velocity with which it would issue from an orifice : and as 

 the velocities are as the square roots of the depths of the 

 orifices, the greatest velocity must be at the bottom of a stream 

 and the least at the surface, besides a continual acceleration of 

 the river as it moves. It was in vain that he attempted to 

 reconcile these principles to facts. But the great work of Gu- 

 glielmini is his Natura de'Mumi, which was published with 

 notes by Manfredi in the year 1697, and followed by a second 

 part in the year 1712, after his death. The first three chapters 

 contain definitions and general notions on the equilibrium of 

 fluids, and the origin of fountains : the fourth and fifth chap- 

 ters relate to the motions of rivers down inclined planes, 

 with reference to friction and resistance, by which an equili- 

 brium is established between the force of the current and 

 the resistance of the bed. He states, that the inclination and 

 velocity of rivers continually diminish in proportion as the 

 rivers recede from their sources, and that consequently the 

 power of transporting matei'ials and the magnitude of the 

 materials themselves diminish in a corresponding ratio ; — that if 

 there be two rivers of equal velocities, but of unequal masses, the 

 river which has the greatest mass will have the least inclination : 

 and from data not satisfactory he deduces that the greater the 

 body of water in rivers, the less will be the inclination of their 

 beds. 



Chapter the 6th relates to the direction of rivers, and to the 

 difficulty of restraining and regulating their courses ; and in a 

 series of propositions and corollaries the author demonstrates, 

 That the direction of rivers is necessarily rectilinear if not in-r 



1834. 2f 



