[310] Menzel, H. C. 258, 1924.

[311] J. Op. Soc. Am., 9, 335, 1924.

[312] Catalan, Phil. Trans., 223A, 127, 1922.

[313] Chapter VIII, [p. 124].

[314] H. C. 238, 1924.

[315] J. Op. Soc. Am., 9, 355, 1924.

[316] Phil. Trans., 223A, 127, 1922.

[317] Walters, J. Op. Soc. Am., 8, 245, 1924.

[318] Chapter VIII, [p. 125].

[319] Ibid.