As the published facts concerning the rate of mortality in tropical Africa are very scanty, and Insurance Offices are therefore often compelled to fix the extra premiums for African risks in an almost purely arbitrary manner, I venture to lay the following investigation before the members of the Institute as a contribution to our knowledge of the subject. So far as I am aware, the only publications dealing with the subject are a note by my father, Dr. T. B. Sprague, on the Rate of Mortality on the Congo (J.I.A. xxv, 437); a note read by myself before the Actuarial Society of Edinburgh on the Rate of Mortality in Sierra Leone (Transactions, iii, 365); a paper by Mr. J. R. Hart on the Mortality on the West Coast of Africa, which appeared in the Insurance Record of 2 October 1896; and a paper by Dr. T. Glover Lyon on the Mortality amongst Europeans in certain Unhealthy Districts (J.I.A., xxix, 541).