midnight
And these were really found in the ruins of St. Ruth ? '' `` Most assuredly -- my own eyes witnessed it . '' `` Well , '' replied Oldbuck ; `` but you must tell me the when -- the where-the how . '' `` The when , '' answered Sir Arthur , `` was at midnight the last full moon -- the where , as I have told you , in the ruins of St. Ruth 's priory -- the how , was by a nocturnal experiment of Dousterswivel , accompanied only by myself . '' `` Indeed ! '' said Oldbuck ; `` and what means of discovery did you employ ? '' `` Only a simple suffumigation , '' said the Baronet , `` accompanied by availing ourselves of the suitable planetary hour . ''