1. The use of the same symbol D to denote both diameter and drag will not be found to introduce any confusion, since both will not occur in the same equation.
2. A more exact discussion of this problem is given by J. M. Bürgers in Proc. Kon. Ak. v. Wet. Amsterdam, Vol. 32, No. 9, p. 1278, 1929.
3. See Riemann-Webers Differentialgleichungen der Physik, Vol. I, Chap. XIV, Braunschweig, 1925.
4. This relation may be obtained by introducing the first of (2.2) in the first of equations (1.12) of Division L II.
5. Experiments with a Family of Airscrews, Part I. Br. A.R.C. R. and M. 829, Vol. I, 1922–23.