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city of the water is encreafed after its difcharge, though the 

 atflual velocity of the feveral particles continues unvaried, may be 

 thus explained : the particles which iffue near the fides of the 

 oriiice proceed converging towards the axis of the vein, and with 

 a retarded motion, upon account of their attrition againft the 

 fides of the orifice ; and as the central particles move fafter 

 than thofe which are farther from the axis, each plate of water 

 after leaving the orifice, will afi'ume a curved form, the concavity 

 of which will refpedt the orifice. Let E F be the diameter of 

 the vein where narroweft, and AB the diameter of the orifice ; 

 the fine of particles A B, which leave the orifice at the fame, inftant, 

 will afiTume a curvilineal pofition EGF, the central particles at 

 G moving fafler than the extreme ones at E and F ; the particles, 

 therefore, in the diameter' of the vein between E and F are 

 fupplied from the plates of water which ifiTued fucceflively after 

 EGF J and thefe extreme particles being thus diminifhed in number, 

 the central particles continuing nearly the fame, the mean velocity 

 muft be encreafed, becaufe that velocity is found by dividing the 

 fum of the velocities of all the particl.s by their number, and the 

 number of particles which move with the greatefl velocity bears 

 a greater proportion to the whole number in the narrow fedion 

 of the vein at E F than in the orifice. In fliort, to cxprefs my- 

 felf perhaps more clearly, the particles in the diameter A B, 

 without being accelerated after their exit from the orifice, pafs 

 through a lefs fpace, becaufe they arrive at that fpace in dif- 

 ferent times. It appears, therefore, that the a£lual velocity of 

 the effluent water is not encreafed after its difcharge from the 

 orifice, the contra£lion of the vein not inferring any fuch aug- 

 mentation, and there being no caufe by which it could be pro- 

 duced. 



