MR. RENNIE ON THE FRICTION AND RESISTANCE OF FLUIDS. 429 
Conclusions. 
1. That the friction or adhesion of water against the surfaces of solids in motion, approximates the 
ratio of the surfaces with slow velocities ; but that an increase of surface does not materially affect it 
with increased velocities. 
2. That with equal surfaces the velocities do not seem to observe any fixed ratio, but approximate 
to the squares of the resistance. 
With increased velocities the index of the power was found to be less than the duplicate ratio. 
To exemplify the result of the foregoing conclusion in a different way, — the 
cylinder was removed, and circular discs of iron, ten inches and three quarters 
diameter and one eighth of an inch thick, accurately adjusted to the spindle 
and polished, were substituted. The friction of the apparatus was again tried, 
and immersed in the river Thames, as before. 
Table II. (See Plate XII. Fig. 2.) 
Experiments on the Friction in Water of Circular Discs ten inches and three 
quarters in diameter and one eighth of an inch thick, revolving with the 
planes parallel to the horizon, and six inches apart. 
Number 
of discs. 
Weight 
suspended. 
Height fallen 
of weight. 
Time of 
weight de- 
scending 
in water. 
Velocity of 
periphery 
per second. 
Time de- 
scending 
in air. 
Velocity of 
periphery 
per second 
in air. 
Difference . 
lbs. 
lbs. 
seconds. 
inches. 
seconds. 
inches. 
seconds. 
1 
1 wenty-five 
10.00 
42.200 
8.00 
2 
circle 16.88 
5.00 
84.400 
3.00 
1 
3 
would move 
3.00 
140.660 
2 
211 
1.00 
4 
through 422 
3.00 
140.660 
1.00 
6 
inches. 
3.00 
140.660 
1.00 
1 
15.00 
28.133 
13.00 
2 
6.50 
64.923 
4.50 
2 
3 
Ditto. 
4.50 
93.770 
o 
211 
2.50 
4 
4.00 
105.500 
2.00 
6 
4.00 
105.500 
2.00 
1 
17.00 
24.823 
15.00 
2 
7.00 
60.285 
5.00 
3 
3 
Ditto. 
5.50 
76.727 
2 
211 
3.50 
4 
4.00 
105.500 
2.00 
6 
3.00 
140.660 
1.00 
1 
33.00 
12.787 
31.00 
2 
17.00 
24.823 
15.00 
4 
3 
Ditto. 
8.00 
52-750 
2 
211 
6.00 
4 
6.00 
64.923 
4.00 
6 
4.00 
105.500 
2.00 
