Wonderful little piece of Abolition ephemera and history. 

Bielby Porteus [1731-1809] was the Bishop of London and the earliest and most significant voice within the Church of England's clergy structure arguing for the aboltion of the Slave Trade. Acting as the Corresponding Secretary at Lambeth Palace as a young Priest, he corresponded with the missionaries in the West Indies and Americas; these correspondences often included first-hand reports of the treatment of the "labour force" that was building the British Empire. 

He was unique in the Church of England in his openness to working with the heirs of the Great Awakening, i.e. Wilberforce, Newton, Hannah More, etc.,] By 1776, he was using his role and influence to rid the SPG of any connection to slaves and plantations in Barbados, Jamaica, etc. and his preaching routinely and increasingly became focused on the moral, systemic sinfulness of British society's success at the hands of slave labor and traffic. At the emergence of the Clapham Sect, he lent them his full public and private support; a radical move for an influential clergyman to a movement including so many dissenters. 

He was, no doubt, God's man on the inside of the Anglican church to help move it toward support for the abolitionist cause. 

The Whole Book of Psalms, Collected into English Metre, by Thomas Sternhold, John Hopkins, and Others. Cambridge, Joseph Bentham. 1765. 

[bound with]

A New Edition of the Psalms of David Fitted to the Tunes Used in Churches by Brady and Tate. London. Edward Say. 1765. 

Original highly decorative polish calf, rubbed, replaced endpapers probably in the 19th century, blank ffep has in the hand of Porteus, "My Psalms" followed by a list of those that are of apparently particularly personal use. Then "Parish Psalms" with another list. It is then signed by Porteus with a note below it, in 19th century hand, describing its provenance. The blank ffep prior to title then includes a full page manuscript of "An Evening Hymn," i.e. "Glory to Thee, my God this night . . . " The corresponding "Morning Hymn" is written on the blank rfep. These both apparently in his hand. There is a manuscript hymn between the two works as well, that seems to not be in Porteus' hand. Rear board present but detached.