6 
Mr. Vince’s Experiments on the Resistance 
therefore the resistance on the flat side of a semi-globe : the 
resistance of a cylinder of the same diameter, and moving 
with the same velocity : : 0,08339 : 0,07998. This difference 
can arise only from the action of the fluid on the back side 
of the semi-globe, moving with its flat side forwards, being less 
than that on the back of the cylinder, in consequence of which 
the semi-globe suffered the greater resistance. The resistance 
of the cylinders, thus determined directly by experiment, agrees 
very well with the foregoing experiments. The resistance, 
cceteris paribus , varies as the square of the velocity very nearly, 
and may be taken so for all practical purposes, as I find by 
repeated experiments, made both upon air and water, in the 
manner described in my former paper. Hence, for different 
planes, the resistance varies as the area x the square of the ve- 
y • /,?$ 3 locity. Now the resistance of the planes whose area was 3,73 in. 
moving with a velocity of o ,66 feet in a second, was found to 
be = 0,2321 oz. Also, the area of the two cylinders was 1,9 in. 
and their velocity was 0,542 feet in a second ; to find, there- 
fore, the resistance of the cylinders from that of the planes, 
we have o,66 2 x 3,73 : 0,542* x 1,9 :: 0,2321 oz : 0,07973 oz. 
for the resistance on the cylinders, differing but a very little 
from 0,07998 oz. the resistance found from direct experiment. 
Now, to get the resistance on a perfect globe, we must con- 
sider, that when the back part is spherical, the resistance is 
greater than when it is flat, in the ratio of 0,08339 : 07998 ; 
hence, the resistance on a globe : the resistance on a semi- 
globe in the same ratio ; but the resistance on the semi-globe 
was 0,034 oz. hence, 0,07998 : 0,08339 : : 0,034 oz. : 0,0354 
oz. the resistance of a globe ; consequently, the resistance of a 
globe : the resistance of a cylinder of the same diameter, mov- 
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