It contains a plan, or critical delineation, of what he himself esteemed the most finished Eloquence, or style of Speaking. He calls it _The Fifth Part, or Book_, designed to complete his _Brutus_, and _the former three_ on the same subject. It was received with great approbation; and in a letter to Lepta, who had complimented him upon it, he declares, that whatever judgment he had in Speaking, he had thrown it all into that work, and was content to risk his reputation on the merit of it. But it is particularly recommended to our curiosity, by a more exact account of the rhetorical _composition_, or _prosaic harmony_ of the ancients, than is to be met with in any other part of his works.