[ l6 3 ] 
It appears from the preceding collection of ex- 
amples, that when the extremities of the Dutch fails 
are parallel to the plane of motion, or at right angles 
to the wind, and to the axis, as they are made accord- 
ing to the common practice in England , that their 
velocity, unloaded, is above 4 times, and loaded to 
a maximum , above 3 times greater than that of the 
wind : but that when the Dutch fails, or enlarged 
fails, are in their belt pofitions, their velocity un- 
loaded is 4 times, and loaded to a maximum , at a 
medium the Dutch fails are 2,7, and the enlarged 
fails 2,6 times greater than the velocity of the wind. 
Hence we are furnifhed with a method of knowing 
the velocity of the wind, from obferving the velocity 
of the windmill fails j for knowing the radius, and 
the number of turns in a minute, we fhall have the 
velocity of the extremities ; which, divided by the 
following divifors, will give the velocity of the 
wind. 
Dutch fails in their common pofition I 4 - 2 
Dutch fails in their belt pofition — 5 ^ uHlo.td^d 4.0 
r [loaded — 2.7 
Enlarged fails in their bed; pofition { loaded ' ^ 26 
From the above divifors there arifes the following; 
compendiums ; fuppofing the radius to be 30 feet, 
which is the mod; ufual length in this country, and 
the mill to be loaded to a maximum , as is ufually the 
cafe with corn mills ; for every 3 turns in a minute , 
of the Dutch fails in their common pofition , the wind 
will move at the rate of 2 miles an hour ; for every 
y turns in a minute , of the Dutch fails in their be ft 
Y 2 pofition , 
