1. McCall, G. J. H., Nature, 194, 343 (1962).
2. Temperley, B. N., and Bristow, C. M., Tech. Rep. 5 (Hydraulic Branch, Ministry of Works, Kenya) (in the press).
3. Bristow, C. M., Tech. Rep. 6 (Hydraulic Branch, Ministry of Works, Kenya) (in the press).
4. Bristow, C. M., Geol. Mag., 99, 153 (1962).
5. Marshall, P., Trans. and Proc. Roy. Soc. N.Z., 64, 323 (1935).