t = .35d, d = 0.22 to 0.25 [root](Q/[root]p) ft.
t = .45d, d = 0.20 to 0.22 [root](Q/[root]p) ft.
N = 1203 [root]p/d.
These approximate equations, which are derived purely from experiment,
do not differ greatly from those obtained by the rough theory given
above. The theory helps to explain the reason for the form of the
empirical results. (W. C. U.)