222 
James Small. 
overtakes the wind at not less than 60 m.p.h. it stays up, and so long 
as the wind overtakes the fruit at not less than P44 m.p.h. the fruit 
stays up. 
Winds between “ W” and “V .”—If tiie wind exerts a pressure 
of‘0107 gms. per sq. cm. the fruit is blown right through the tube 
without touching, and if the wind exerts a pressure of ‘0026 gms. 
per. sq., cm. or less, the fruit does not move once it has fallen. 
Between these two points the fruit moves but touches the tube, 
and it is of interest to follow the action of the wind with pressures 
between VV and V. 
In the initial stages of flight the wind exerts its full pressure, 
i.e., M—W, but as soon as it has developed an effective action 
the fruit moves and M becomes less than W. Since the continued 
flight depends on V being not less than the critical value the fruit 
will fall: thus if W=’0052 gms. per. sq. cm. M will be less than that 
and V will be less than -0026 per sq. cm., which is the minimum 
vertical component which keeps the fruit up ; the fruit will therefore 
fall. When reference is made to Table X it will be noted that if W 
is greater than '0052 gms. per sq. cm. the fruit moves along con¬ 
tinuously but is partly supported by the tube. It is only when W 
falls below the minimum value of M that the fruit actually stops. 
If W is less than -0052 gms. per sq. cm, then V can never, 
even in the initial stage, be as much as ‘0026 gms. per sq. cm., 
so that the fruit must fall; but the time taken to fall will depend 
on the upward pressure exerted by the vertical component. The 
fruit will fall slowly if V is nearly ’0026 gms. per sq, cm., and more 
quickly the smaller the value of V becomes. 
The value of V depends on the value of W and on the value 
of 0. The product cos# x sin# diminishes gradually until when the 
fruit is vertical it is nothing. The smaller W becomes the greater# 
becomes, because the pappus is not blown so much before the 
fruit body, so that the smaller W becomes the smaller becomes 
cos# x sin#, and therefore V becomes smaller very rapidly. 
As soon as W is equal to the rate of fall in quiet air the 
axis of the fruit becomes vertical; then there is no vertical com¬ 
ponent of W and the fruit falls with a velocity equal to that of the 
wind. The initial elevation is then equal to the distance travelled 
by the fruit. This may be made clear by considering the parallelo¬ 
gram of forces in Pig. 27, D. The force X is equal to the force Y, 
and they act at right angles to each other, the resultant is AC, 
which is the path of fall of the fruit. It is then clear that AB=BC, 
