Substance of the speeches of the Right Honourable William Pitt, on the 23rd and 31st of January 1799 : including a correct copy of the plan, with the debate which took place in the House of Commons on the proposal for an union between Great Britain and Ireland : to which are annexed, The celebrated speeches of the Right Honourable John Foster ... on the 12th and 15th days of August 1785, upon the commercial propositions