<=> 0 >^ 0 o» 
THE AERODYNAMICS OE A SPINNING SHELL. 
349 
multiples of 7 r, which are alternatively odd and even in successive periods of 8, the 
points can be fitted roughly to a straight line of constant slope. All the points will 
lie fairly well on this straight line, except those in the immediate neighbourhood of 
the minima of 8. By producing this straight line backwards we can determine the 
initial value of <p. The slope of the straight line determines an independent value 
of Q, which is equal to the value deduced from the muzzle - velocity if the slope 
is 0-5. 
