28 \SUMMARY OF HYDRAULICS. 



may be increafed by the addition of a conical tube nearly in the 

 ratio of 5 to 2 ; but Mr. Eytelvvein finds this alfertion fome- 

 what too ftrong, and obferves, that when the pipe is already 

 very long, fcarcely any effect is produced by the addition of 

 fuch a tube. He proceeds to defcribe a number of experi- 

 ments made with different pipes, where the ftandard of com- 

 parifon is the time of filling a given veffel out of a large refer- 

 voir, which was not kept always full, as it was difficult to avoid 

 agitation in replenifliing it, and this circumftance was perfectly 

 jncreafes the dif- indifferent to the refults of the experiments. They confirm the 

 fimpfe aperture a "** e rtion that a compound conical pipe may increafe the dif- 

 twice and a half, charge to twice and a half as much as through a fimple orifice, 

 or to more than half as much more as would fill the whole fec- 

 tion with the velocity due to the height: but where a consi- 

 derable length of pipe intervenes, the additional orifice ap- 

 pears to have little or no effect. 



The chapter concludes with a general table of the co- 

 efficients for finding the mean velocity of the water difcharged 

 by thepreffure ofa given head under different circumflances. 

 Multipliers for For the whole velocity due to the height, the coefficient, by 

 determining the wh ; ch j ts f quare root ; s to fr Q multiplied, is 8.0458. 

 velocity under * , r 



different cir- For an orifice of the form of the contracted ft ream , 7 . 8 . 



cumftances. For wide openings, of which the bottom is on a level with 



that of the refervoir; for fluices with walls in a line with the 

 orifice ; for bridges with pointed piers, 7.7. 



For narrow openings, of which the bottom is on a level 

 with that of the refervoir, for fmaller openings in a fluice with 

 fide walls, for abrupt projections and fquare piers of bridges, 

 6.9. 



For fhort pipes from two to four times as long as their dia- 

 meter, 6.6. 



For openings in fluices without fide walls, 5.1. 

 For orifices in a thin plate, 5. 



Chapter 2. Of the difcharge of water by horizontal and by 

 fmall lateral orifices, in a veffel continuing full. 

 Particular cafes. The principles detailed in the firft chapter are here applied 



to particular cafes. 

 Difcharge Chapter 3. Of the difcharge by rectangular orifices in the 



through a notch ride ofa re f ervo j r> extending to the furface. 



The velocity varying nearly as the fquare root of the height, 



may here be reprefented by the ordinates of a parabola, and the 



4 quantity 



