James Small. 
216 
axis of the fruit with the horizontal (see Pig. 27, B). The tangential 
component S is known in kite dynamics as surface slip and is 
usually considered negligible. 
Fig. 27. Resolution of Forces (for explanation see text). 
The Vertical Component. —The normal component R can he 
resolved further into two components (Fig.27,C) a vertical component 
V and a horizontal component H. The vertical component V is 
equal to R sin# and the horizontal component H to R cos#. 
Since R=M cos#, R sin#= M cos# sin#, therefore V=M cos# sin#. 
If the pappus surface were a continuous membrane or acted as a 
continuous membrane (of the area occupied by the hairs and the 
interspaces) and if the wind were just sufficient to keep the 
movement of the fruit horizontal the vertical component would be 
equal to the mass of the fruit. As the pappus is not a continuous 
membrane the minimum pressure on the area of the circle of the 
pappus surface may be greater than the weight of the fruit. This 
minimum pressure is described below as the critical vertical 
component, which is of course a pressure, not a velocity. 
The Horizontal Component. The horizontal component is equal 
to R cos#, which is equal to M (cos#) 2 . 
Surface Slip. The component S can be resolved into a 
horizontal and a downward vertical component. These will be 
equal to x S sin# and x S cos# respectively; where x is a small 
fraction. The close similarity of the experimental and the 
calculated results (see Table XI) shows, that x is so small that S can 
be neglected. 
Data, 
For any further consideration various data are necessary and 
these have been obtained. 
Weight of the Fruit. Bessey (5) gives -00044 gms as the weight 
of the dandelion fruit but it was considered necessary to determine 
the weight of the fruits actually used. One hundred whole fruits 
Were weighed carefully. 
