Origin and Development of the Composites. 209 
of the anemometer, and it was found that there was a hollow cone 
of relative calm near the centre of the fan with Speed 4; this cone 
extended about 10-15 cms. from the boss of the fan. Beyond 20 
cms. the wind had a steady horizontal pressure, and with lower 
speeds no cone of calm could be detected. 
It was further found that the pressure of wind in the tube 
at the end furthest from the fan was practically the same as the 
pressure obtained without the tube and with the anemometer 
130 cms. nearer the fan. 
As it was not possible to measure all the variations of 
pressure obtained the relation of the pressure of the wind to the 
distance from the fan was examined. A series of measurements 
of the pressure with the tube at various distances from the fan showed 
that within the limits of the experiments the pressure of the wind, 
except for Speed 4, varied approximately inversely as the distance 
of the near end of the tube from the fan. The measurements and 
ratios are given in Table IX. It is possible, therefore, to calculate 
from a few measurements the pressure at any given distance. 
Table IX. 
Speeds of Fan. 
Distance of Tube 
Pressure on Disc 
as measured. 
Ratios 
Speed 1. 
26'5 cms. 
•18 gms. 
10 : 1125 
» 9 
30 5 „ 
•16 „ 
1-150 : 10 
Speed 2. 
29-5 cms, 
•36 gms. 
10 : 2.25 
44-5 „ 
•26 „ 
1-5 : 1.6 
9 9 
75-5 „ 
•16 „ 
2-5 : 1-0 
Speed 3. 
26 5 cms. 
•56 gms. 
1-0 : 3-5 
40-5 „ 
•36 ,, 
1-5 : 2-25 
63 5 ,, 
•26 „ 
2.4 : 1-6 
9 9 
103-5 ,, 
•16 „ 
3-9 : 10 
Speed 4. 
28 5 cms. 
•50 gms. 
10 : 31 
87-5 „ 
•25 ,, 
3-0 : 16 
9 9 
144-5 „ 
•16 ,, 
50 : 10 
Since within the limits of the experiments P=kV, where P 
p 
is the pressure, V the velocity and k a constant, V=—■. The 
constant k in these experiments is taken as ’0025 gms., which is 
the pressure on one sq. cm. of a wind with a velocity of one m.p.h. 1 
1 This is calculated from the constant given by llerget (4), velocity of 
1 metre per second*=pressure of 125 gms. per sq, metre. This figure is also 
approximately the same as the theoretical pressure calculated from the 
density of the air. 
