HYDRAULICS. 



is considered to be nearly at rest all 

 around it. Other circumstances be- 

 sides friction likewise tend to diminish 

 the quantity of fluid which would other- 

 wise pass through pipes, such as the 

 existence of sharp or right-angled turns 

 in them, and permitting eddies or cur- 

 rents to be formed, or not providing for 

 the eddies or currents that form natu- 

 rally by suiting the shape of the pipe to 

 them. * It follows therefore that, when- 

 ever a bend or turn is necessary in a 

 water-pipe, it should be made in as gra- 

 dual a curve or sweep as possible, in- 

 stead of the form of an acute or even 

 right angle ; that the pipe should not 

 only be sufficiently capacious to afford 

 the necessary supply, but should be of 

 an equal bore throughout, and free 

 from all projections or irregularities, 

 against which the water can strike and 

 form eddies or reverberations, since 

 these will impede the progress of the 

 fluid as effectually as the most solid ob- 

 stacles. These subjects have been par- 

 ticularly investigated and examined by 

 Newton, Bernoulli d'Alembart, De 

 Buat, Robison, Venturi, Dr. Young, and 

 many others : and the following impor- 

 tant* practical results obtained from 

 their labours are highly worthy of at- 

 tention : 1 st. The friction of water in 

 rivers or channels increases as the 

 square of the velocity. 2nd. Although 

 the sides of a pipe must in every case 

 produce a certain degree of friction, yet 

 that defect is frequently overbalanced 

 by a duly-proportioned size of pipe pro- 

 perly fixed, savins: a moving direction to 

 the fluid which it would not otherwise 

 obtain, and by which a greater quantity 

 of discharge is produced than could 

 otherwise take place. Thus, for ex- 

 ample, a vessel or reservoir, having a 

 thin bottom of tin, with a smooth cir- 

 cular hole formed therein, might be 

 supposed most capable of parting ra- 

 pidly with its water, because the fluid in 

 running out has no continued length of 

 substance to rub against, and conse- 

 quently it might be Imagined that very 

 little friction could be generated ; but M. 

 Yenturi found by his experiments, that 

 such a vessel did not discharge its water 

 so rapidly as another containingthe same 

 height of water and area of hole to 

 which a short pipe of the same diameter 

 as the hole was applied, and by varying 

 the length of pipe he ascertained, that 

 when its length was equal to twice its 

 diameter it produced the most rapid 

 discharge, for being so circumstanced 



it discharged eighty-two quarts of water 

 in 100 seconds, while the simple hole, 

 without the pipe, discharged but sixty- 

 two quarts in the same time. Pursuing 

 the same experiments, he found that 

 if the pipe, instead of being applied to 

 the bottom of the reservoir, so as to be 

 flat and even with it, was made to 

 project some distance into it as at p, 

 in the vessel A, /#. 1 , it had the effect 

 of diminishing the flow of water even 

 to less than issued through the sim- 

 ple hole without any pipe. This 

 phenomenon of a pipe and hole, of 

 similar area, discharging various quan- 



fig.l. 



tities of water under different circum- 

 stances, while the head or pressure re- 

 main the same, is sufficiently accounted 

 for by the cross or opposing currents 

 in which all fluids move, when the con- 

 ducting pipes or vessels are formed so 

 as to oppose or divert the assisting 

 currents that would otherwise form : 

 thus currents will form from the top 

 and sides of the containing vessels to- 

 wards the orifice of discharge, as indi- 

 cated by the direction of the long dots, 

 drawn within the vessel shown in sec- 

 tion at B,Jig. 1 . The direction of these 

 dots do not, however, stop at the dis- 

 charging orifice, but, from the inertia 

 of water, are constrained to cross each 

 other and pass beyond it ; hence to a 

 certain extent they tend to stop or shut 

 up the orifice against the passage of 

 that water that is descending more per- 

 pendicjiilarly, and by their contending 

 influence cause the water that issues to 

 run in a screw -like form. This effect 

 is in a great measure counteracted and 

 destroyed by the application of a short 

 tube below the hole, but if that tube 

 projects into the vessel as at A, 

 the dots assume a new form, and those 



