For statute miles per hour--Observe the number of paces (n) taken in 5.7
seconds: let i be the number of inches (to be subsequently determined at
leisure) in a single pace; then ni/100 is the rate per hour.
For geographical miles per hour--The number of seconds to be employed is
5. This formula is therefore very simple, and it is a useful one. (A
statute mile is 1760 yards, and a geographical mile is 2025 yards.)
For finding the rate in statute miles per hour in a carriage--Observe
the number of revolutions (n) made by the wheel in 18 seconds: let d be
the number of inches in the diameter of the wheel; then n d/200 is the
rate per hour.
The above method is convenient for measuring the rate at which an animal
gallops. After counting its paces it may be through a telescope, during
the prescribed number of seconds, you walk to the track, and measure the
length of its pace. If you have no measuring tape, stride in yards
alongside its track, to find the number of yards that are covered by 36
of its paces. This is, of course, identical with the number of inches in
one of its paces.
Convenient Equivalents.--The rate of 1 mile per hour, is the equivalent
to each of the rates in the following list:--
Yards. Feet. Inches.
29.333, or 88.000, or 1056.000, in one minute
or 0.488, or 1.466, or 17.600, in one second
Measurement of Length.
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