MR. RENNIE ON THE FRICTION AND RESISTANCE OF FLUIDS. 433 
side of the cistern, and closed by a valve of brass ground to each of the plates. 
The valve was opened by a lever, and the time noted by chronometers. 
The diameters of the tubes, from having been drawn on mandrils, were as 
accurate as possible; their diameters at the extremities were carefully enlarged, 
to prevent any wire edges from diminishing their sections ; and one extremity 
of the tube being inserted into a block of hard wood fastened to the cistern, 
and the other stopped by a valve, the experiments were recorded as before. 
Table V. 
Experiments on the Quantity of Water discharged by different-sized Orifices 
from a vessel kept constantly full and at different heights. 
Circular Orifice made in a brass plate 1 inch diameter, ^ inch thick. 
Constant height of 
the surface of the 
water above the 
centre of the orifice. 
Real time in dis- 
charging one cubic 
foot. 
Theoretical time 
in discharging one 
cubic foot, 
, <1 
Ratio of the theo- 
retical to the real 
discharges. 
Vena contracta. 
2AVgH 
feet. 
4 
3 
2 
1 
seconds. 
19.50 
21 
26 
36 
seconds. 
11.4 
13.2 
16.1 
22.8 
1 : .584 
1 : .628 
1 : .619 
1 : .633 
Not accurately measured. 
Circular Orifice in a brass plate \ inch diameter, -cVth inch thick. 
4 
33 
20.3 
1 : .614 
At six tenths of an inch 
3 
37 
23.4 
1 : .632 
from the orifice, the di- 
2 
44 
28.7 
1 : .652 
ameter had contracted to 
0.685 of an inch. 
1 
63 
40.6 
1 : .644 
Circular Orifice in a brass plate \ inch diameter, ^th inch thick. 
4 
73 
45.7 
1 : .626 
At half an inch beyond the 
3 
83 
52.8 
1 : .636 
orifice, the diameter con- 
2 
104 
64.6 
1 : .621 
traded to 0.37 of an inch. 
1 
144 
91.4 
1 : .634 
Circular Orifice in a brass plate 4 inch diameter, -cVth inch thick. 
4 
276 
182.9 
1 
.662 
3 
320 
211.3 
1 
.660 
2 
396 
258.6 
1 
.653 
1 
545 
365.7 
1 
.671 
At a quarter of an inch be- 
yond the orifice, the di- 
ameter contracted to one 
twentieth of an inch less 
than the orifice. 
N.B. Each result shows the mean of four experiments. 
Remarks. 
The phenomena relative to the form and direction of veins of spouting fluids, and the remarkable 
inversion of the fluid veins at certain distances from their orifices, have been so fully noticed in 
“ Experiences sur la Forme et sur la Direction des Veines et des Courans d’Eau ; par George Bidone : 
Turin, 1829,” that it is unnecessary to state further than that they have been completely corroborated 
in the foregoing experiments. 
3 K 2 
