176 THIRD REPORT — 1833. 



He then determines, from the results of M. Venturoli*, the 

 absolute magnitude of the contracted section of the vein (issuing 

 from a circular orifice) to be exactly f rds of the orifice, the 

 correction due to the contraction depending upon the ad- 

 hesion and friction of the fluid against the perimeter of the ori- 

 fice, and the ratio of the area of the vein to the area of the 

 orifice : the same for all orifices. Hitherto the magnitude of 

 fluid veins, as determined by direct measurements, had given 

 greater coefficients than the effective expenditure allowed. 



Michelotti, with a pressure of twenty feet, with orifices of one 

 and two inches in diameter, found the coefficient 0*649 



Bossut 0-660 



Borda 0-646 



Venturi 0-640 



Eytelwein 0-640 



Hachette 0-690 



Newton 0-707 



Helsham 0-705 



Brindley and Smeaton 0-631 



Banks 0-750 



Rennief 0-621 



In several experiments the ratio rarely exceeded 0-620 ; so 

 that the discrepancy must have arisen from inaccuracies in the 

 measurement of the fluid vein and orifice. 



In the year 1827, it having been considered desirable to re- 

 peat the experiments of Bossut and Dubuat, application was 

 made to the French Government by General Sabatier, Com- 

 mander-in-chief of the Mihtary School at Metz, for permission 

 to undertake a series of experiments on a scale of magnitude 

 sufficient to estabhsh the principles laid down by those authors, 

 and serve as valuable practical rules for future calculations. 

 The apparatus consisted, 1st, of an immense basin, having 

 an area of 25,000 square metres ; 2nd, of a smaller reservoir, 

 having a superficial area of 1 500 square metres, and a depth 

 of 3-70 metres, so contrived, by means of sluices, as to have a 

 complete command of the level of the water during the experi- 

 ment ; 3rd, of a basin directly communicating with the second 

 basin, 3-68 metres in length, and 3 metres in width, to receive 

 the product of the orifices ; 4th, a basin or gauge capable of 

 containing 24,000 litres. 



* Elementi di Meccanica e d'Idraulka: Milano 1818. Recherche Geome- 

 triche fatte nella Scuola degli Ingegneri pontifici d'Acque e Strode, Fanno 

 1821. Milano. 



t "On the Friction and Resistance of Fluids," Philosophical Transactions of 



1831. 



