The 1877 Convention abolished slave trade but not slavery itself.

Evidence

The members of the Society were also well aware that they had public opinion on their side. The pressure they exerted, which often had the support of members of Parliament, resulted in the Anglo-Egyptian Convention of 1877, which abolished the trade in African slaves in all territory held by the Egyptian government, although it did not outlaw the institution of slavery itself. The Anti-Slavery Convention was posted by decree throughout Egypt’s cities and the Sudan, and allowed for the creation of slave trade bureaus in Cairo, Alexandria, the Delta, and Upper Egypt. These bureaus were intended not only to record the manumission of individual slaves but also to find suitable employment for freed slaves and possible education for their children.The authorities of these bureaus were also responsible for the punishment of “any person depriving a freed slave of his freedom or taking from him his manumission certificate”; such a person was to be handled as a slave dealer. — Eve M. Troutt Powell, A Different Shade of Colonialism_…, 658