DISCHARGE. 
feétion parallel to the bottom be every where the fame, the 
velocity of the {urface of the fluid, 
velocity of the cfilux, will ‘* uniformly re 
rifice to 
conftant in the cafe before us, and the retardat oe 
From this comparifon we deduce the following ot oovicns corol- 
alias 
ae quantities of water in a prifmatic veffel difcharged 
theon h an aperture in the bottom, decreafe in equal times 
as ie feries of odd numbers 1, 3, 5, 7, 9, &c. taken in an 
aes order 
. The uantity of water contained in an upright prifmatic 
veffel i is half that which would be difcharged in the time of 
the entire gradual evacuation 2 the veficl, if the water be 
kept always at the fame altitu 
hoever wifhes to examine oe epee a part of the 
prefent fubje °& more at large, may con the follow- 
o ‘Bernoulli on 
Principles of Hydraulics, ibid. 
water in pipes, N. C. 
Michelici, Borelli, Montanari, Viviani, Caffini, ‘cn 1 
_Grandi, Manfredi, Picard, and Nanducci. on t 
difcharge of fluids. A. 766. Lagrange on the mo- 
tion of flu - Beri, 1781. M. Young on {pouting 
1788 Prony Archit. Hydraulique. 
Lorgna on fponting fluids, Soc. Ital. IV. Venturi fur la 
communication laterale de mouvement dans les fluides. Par. 
“98. oung on the difcharge of a vertical pipe. Journ. 
R. J. Boffut’s Hydrodyn. Gregory’s Mechanics. b. 4. 
now proceed to treat of the experimental part 
of i et fubjeG ; and with refpe& to this we fhall only 
advert to the more important experiments and the moft ule- 
ful refults 
ae ream of water which iffues out of a hole tends to 
away in its direCtion other ftuid, or any other body 
“foliciently light, which may happen to be near it. This is 
what profeffor Venturi ca il the lat pal es of mo- 
tion in fluids. But by this lateral comm nication of motion 
ies, the celerity of ri fluid itfeif is 
d its c ae is partly diverted — 
ae salar which it would otherwife follow. ‘Thus, i 
ich fae the upper furface ef two veffels con- 
and full of water, as High as the hole 
ouring more water into the veifel 
,a 
veffel C, this —— will carry away the water from the paris 
ees towards C. t the depreffion, or deficiency, of water 
‘at ¢e, is replaced be the water from the adjacent Base a2 
which are replenifhed from the next, and fo on. Thi 
duces eddies at ed, ed. ‘This phenomenon may be ida 
more apparent by throwing a little milk into the veflel B, or 
8 
and, ee ade the’ wate 
by letting {mall light bodies float upon the furface of the 
water. 
When a ftream comes out of a hole, as at A, fig. 9, if a 
- ead, one or other light body be placed very “net 
t, the ne of the ftream to carry it tov be 
his tendency is ftill more evidently 
eoilenon AD B, . 10, having one flant fide. Leta 
oF ndrical pipe, of about half an inch in diameter, and up- 
ards of a foot in length, proceeding from a vefle] C, come 
Rraight down into the veffel A D B, and there let its term! 
nation I'S be bent in the direCtion of the flant fide BD. 
Th's done, fill the vefflel A D B with water, then pour water 
into the veflel C, fo that the water running down the pipe 
It will be found that the 
S K, and this veffel is thereby almoft entirely emptied. 
To o an aper ture on the fide of the veffel A B, Ag. 11, a pipe 
diameter, and little more than five inches in length, 
was PEE in an foreonal direCtion by profeffor Venturi. 
At E, diftant 0.71 inch from the fide of the veffel,,a bent 
glafs tube, E F G, was joined, whofe cavity was opened into 
ant of the pipe, whilft its other extremity was immerfed in 
coloured water, which was contained in a fmall veffel G. 
— 
a 
pipe at D; and in a fhort time the veflel G was 
m : 
This lateral communication of motion takes place whe- 
a - cichargin g alae is directed horizontally, or up- 
wards or downwards, or, in fhort, in every dire&tion, but it 
is more powerful when the ftream is directed downwards, 
which is owing to the tendency that: a defcending ftream bas 
of dividing itfelf in confequence o of falling 
odies ; for that part of the ftream a is juft out of the 
aperture moves with Jefs velocity than that whieh is farther 
off. water Sa out of an aperture in the thin fide or 
bottom of a  yellel, asat A 
@lCOlClratlion 
of the This narrowelt part of the ftream bas been 
. the aa vein (vena contraéa by Newton, yi 
firtt t particular notice of it) trom which place for- 
one oe itream grows larger, and fometimes divides itelé 
into different parcels, 
The diameter of the contraéted vein, or of the narroweft 
part of the flream, has been differently eftimated by different 
obfervers: and probably the difference has been occafioned 
by fome unadverted variation in the fize of the veffcl, thicknefe 
of the fide in which the aperture was made, &c.—Newton 
found that at the diftance of about a diameter of the orifice 
the feGiion of the contra&ted vein was nearly in the fub- 
duplicate ratio of.2 to 1. Polenus-makes the ratio of the 
diameters of the contraction and of the aperture to be as 31 
to 13; Bernouilli, as 5 to 7; Du Buat, as6 to 9; Beffut, 
as 41 to 503 aah as 16to 25; Michelotti, as 4 to 5. 
Venturi nearly as 4 to 5. Venturi ‘alfo obferves that the 
contraction of the irene takes place at a greater diftance 
under 
