Read the excerpt from "The Adventure of the Mysterious Picture." "[T]here is a secret about one of my rooms on which I feel disposed to try an experiment. So, gentlemen, none of you shall know who has the haunted chamber, until circumstances reveal it. I will not even know it myself, but will leave it to chance and the allotment of the housekeeper. At the same time, if it will be any satisfaction to you, I will observe, for the honor of my paternal mansion, that there’s scarcely a chamber in it but is well worthy of being haunted." What technique does Irving use to build suspense in the excerpt?