[ 8. ] 



j^n Enquiry into the different MODES of DEMONSTRATION, 

 hy-mhich the VELOCITY g^SPOUTING FLUIDS has 

 been invejiigated a priori. By the Rev. M. YOUNG, £>.Z>. 

 F. T. a D. and M. R. I. A. 





X HE anticnts, as Dodor Jurin informs us, had no knowledge Read March 

 of any meafure of the flux of water, except that fallacious and '' '^ 

 uncertain meafure derived from a perpendicular feflion of the 

 ftream alone, without any regard to. the velocity with which it 

 flows. Benedid Caftelli, an Italian, and friend of Gallileo, was 

 the firft who opened the way to a true meafure. The necefli'ty 

 ef guarding continually againft the damages from the over- 

 flowings of the rivers in Italy, induced Urban the Eighth, who 

 had invited him to Rome as a teacher of mathematics, to requefl: 

 he would apply himfelf to this fubjed. The refult of his enqui- 

 ries is contained in his treatife entitled Delia mefiira dell' acque 

 ■corretiti ; which meafure he; found to depend, on the area of the 

 fcdion and the velocity of the water conjointly. The funda- 

 mental principle of this and other queftions in hydraulics is the 

 determination of the adual velocity with which water fpouts 



M from 



