In 1776, he had written a letter to a friend in America, who was the possessor of slaves, to dissuade him by a number of arguments from holding such property; and now, when the knowledge of the case of the ship Zong was spreading, he published that letter under the title of Fragment of an Original Letter on the Slavery of the Negroes.
In this same year, Dr.Porteus, Bishop of Chester, but now Bishop of London, came forward as a new advocate for the natives of Africa.

The way in which he rendered them service, was by preaching a sermon in their behalf, before the Society for the Propagation of the Gospel.

Of the wide circulation of this sermon, I shall say something in another place, but much more of the enlightened and pious author of it, who from this time never failed to aid, at every opportunity, the cause which he had so ably undertaken.
In the year 1784, Dr.GREGORY produced his _Essays, Historical and Moral_.

He took an opportunity of disseminating in these a circumstantial knowledge of the Slave Trade, and an equal abhorrence of it at the same time.

He explained the manner of procuring slaves in Africa; the treatment of them on the passage, (in which he mentioned the case of the ship Zong) and the wicked and cruel treatment of them in the colonies.