Surveys in British Central Africa were taken up in 1894; a survey of Lake Nyasa, by Lieut.
In December 1901 the mullah was, however, once more raiding in the neighbourhood of Burao, and in May Wars with 1902 Colonel Swayne led another expedition against the Mullah him, the Somali levies being strengthened by the 2nd Mahomme dKing's African Rifles, consisting of Yaos from Nyasa- Abdullah.
The stream of supply came mainly from the southern Nyasa districts by three or four routes to Ibo, Mozambique, Angoche and Quilimane.
It was believed in 1862 that about 19,000 passed every year from the Nyasa regions to Zanzibar, whence large supplies were drawn for the markets of Arabia and Persia up to 1873.
It is said that, whereas io,000 slaves formerly passed the southern end of the Nyasa every year, in 1876 not more than 38 were known to have been conveyed by that route.