Two letters of the Lord Bishop of London : The first, to the masters and mistresses of families in the English plantations abroad; exhorting them to encourage and promote the instruction of their Negroes in the Christian faith. The second, to the missionaries there; directing them to distribute the said letter, and exhorting them to give their assistance towards the instruction of the Negroes within their several Parishes. To both which is prefixed, An address to serious Christians among ourselves, to assist the Society for Propagating the Gospel, in carrying on this work.