fruitless

“They sought even more thoroughly than the august heirs had done, but it was fruitless.

However, he, like Cæsar Borgia, knew the value of time; and, in order to avoid fruitless toil, he sounded all the other walls with his pickaxe, struck the earth with the butt of his gun, and finding nothing that appeared suspicious, returned to that part of the wall whence issued the consoling sound he had before heard.

It was during these fruitless quests that he, or rather his ally, was seen by peasants, and that the legend of the demon dog received a new confirmation.