1. Astbury, Trans. Far. Soc., 36, 871 (1940).
2. Alexander, J. Chem. Soc., 177 (1939).
3. Adam, ‘Physics and Chemistry of Surfaces”, p. 55 (Oxford Univ. Press, 1938).
4. Ref. (3), p. 64.
5. Alexander and Schulman, Proc. Roy. Soc., A, 161, 115 (1937).