In the year 1762, when he had obtained a still greater store of information, he published a larger work.  This, however, he entitled, A short Account of that Part of Africa inhabited by the Negros.  In 1767 he published, A Caution and Warning to Great Britain and her Colonies, on the Calamitous State of the enslaved Negros in the British Dominions;—­and soon after this, appeared, An Historical Account of Guinea; its Situation, Produce, and the General Disposition of its Inhabitants; with an Inquiry into the Rise and Progress of the Slave-Trade, its Nature, and Calamitous Effects.  This pamphlet contained a clear and distinct development of the subject, from the best authorities.  It contained also the sentiments of many enlightened men upon it; and it became instrumental, beyond any other book ever before published, in disseminating a proper knowledge and detestation of this trade.

Anthony Benezet may be considered as one of the most zealous, vigilant, and active advocates, which the cause of the oppressed Africans ever had.  He seemed to have been born and to have lived for the promotion of it, and therefore he never omitted any the least opportunity of serving it.  If a person called upon him who was going a journey, his first thoughts usually were, how he could make him an instrument in its favour; and he either gave him tracts to distribute, or he sent letters by him, or he gave him some commission on the subject, so that he was the means of employing several persons at the same time, in various parts of America, in advancing the work he had undertaken.

In the same manner he availed himself of every other circumstance, as far as he could, to the same end.  When he heard that Mr. Granville Sharp had obtained, in the year 1772, the noble verdict in the cause of Somerset the slave, he opened a correspondence with him, which he kept up, that there might be an union of action between them for the future, as far as it could be effected, and that they might each give encouragement to the other to proceed.

He opened also a correspondence with George Whitfield and John Wesley, that these might assist him in promoting the cause of the oppressed.

He wrote also a letter to the Countess of Huntingdon on the following subject.—­She had founded a college, at the recommendation of George Whitfield, called the Orphan-house, near Savannah, in Georgia, and had endowed it.  The object of this institution was, to furnish scholastic instruction to the poor, and to prepare some of them for the ministry.  George Whitfield, ever attentive to the cause of the poor Africans, thought that this institution might have been useful to them also; but soon after his death, they who succeeded him bought slaves, and these in unusual numbers, to extend the rice and indigo plantations belonging to the college.  The letter then in question was written by Anthony Benezet, in order to lay before the Countess, as a religious woman, the misery she was occasioning in Africa, by allowing the managers of her college in Georgia to give encouragement to the Slave-trade.  The Countess replied, that such a measure should never have her countenance, and that she would take care to prevent it.