A letter of reproof to Mr. John Cleaveland of Ipswich occasioned by a defamatory libel published under his name, intitled, An essay to defend some of the most important principles in the Protestant reformed system of Christianity, &c.--against the injurious aspersions cast on the same, by Jonathan Mayhew, D.D. in his late thanksgiving sermons on Psalm CXLV. 9. In which, &c.