The source of the Blue Nile : a record of a journey through the Soudan to Lake Tsana in western Abyssinia, and of the return to Egypt by the valley of the Atbara : with a note on the religion, customs, etc. of Abyssinia / by Arthur J. Hayes, L.S.A. (Lond.), medical officer, quarantine office, Suez, and an entomological appendix by E.B. Poulton, LL.D., F.R.S., hope professor of zoology in the University of Oxford