  Ah, yes, this was plainly the right way
out of the difficulty; therefore she set her wits to work at once to
contrive that test.  But it was an easier thing to propose than to
accomplish.  She turned over in her mind one promising test after
another, but was obliged to relinquish them all--none of them were
absolutely sure, absolutely perfect; and an imperfect one could not
satisfy her.