Though his reasoning is flawed and his approach inappropriate as he searches vainly for the purloined letter, the Prefect of Police is nevertheless thorough, persistent, and meticulous. In addition to all of his measurings and probings and examinations with the microscope, he is also careful to examine the cellars of all the houses where he suspects the letter could be hidden. What do we learn about his examination of these subterranean rooms that suggests the degree and intensity of the Prefect's intentions?