1Read at the British Association meeting at Nottingham in September 1937; abstract in Rep. Brit. Assoc. Adv. Sci., 1937, p. 356. A paper on similar lines was also read at the fifth annual meeting of the Society for Research on Meteorites at Denver, Colorado, in June 1937, and printed in Popular Astronomy, Northfield, Minnesota, 1937, vol. 45, pp. 504–507. [M.A. 7–78.] Compare C. Fenner, Australites, Parts I and II. Trans. Roy. Soc. South Australia, 1934, vol. 58, pp. 62–79, 6 pls.; 1935, vol. 59, pp. 125–140 [M.A. 6–18, 208]; and L. J. Spencer, The tektite problem. Min. Mag., 1937, vol. 24, pp. 503–506.