It is a pleasure as well as a duty to begin this work by an attempt to show the indebtedness of which I am fully conscious to the many who have assisted me directly and indirectly in the preparation of this work.<br><br>If it had not been for the care and hospitality of Captain Gibb, the French Fathers in Buddu and on Tanganyika, Mr. Law, Mr. Heard, and the late Dr. Scott in British Central Africa, I should certainly not have survived the expedition.<br><br>In the preparation of it, I must express my thanks first to Mr. A. D. Innes for the numerous suggestions and revisions that have shaped my rough-hewn manuscripts. Dr. Gregory should have the credit of much of the geological portion, and Mr. Butler and Mr. Murray have given me two lists which are now printed in the Appendix.