please explain Virginia and THe Ghost disappear through the wainscoting?

The disappearance of Virginia and the ghost through the wainscoting was a feat achieved by the ghost because it was an intangible form that is it did not have a body. Regarding Virginia,the ghost possibly possessed powers to manipulate matter and that is how she could also disappear. As she opened her eyes, Virginia saw the wall slowly fading away like a mist and a great black cavern opening up in front of her.