“Having advised this petition, and in respect that the interlocutor reclaimed against is founded on the Magistrates of Edinburgh having failed to embrace an opportunity which occurred of acquiring, on terms not unreasonable, the property necessary to complete York-place in the manner it was held out to the feuars thereof, as destined to be completed when such opportunity occurred, and as meant to operate agreeably to the doctrines of law as to mutual contracts, whereby retention operates as a compulsitor for implement, and loco facti imprestabilis succedit damnum et interesse; that the interest of the petitioners is involved by the transactions of the Magistrates; and that the attempt now to impeach grounds in fact, on which