Who is Dr. Lionel Barrett from Hell House and what is their importance?

Dr. Barrett is a physicist who has studied parapsychology for twenty years. He has a neatly trimmed beard and is mildly overweight. He is in his middle fifties, but his blond hair shows no traces of white like his beard does. He is a tall man and sits erect. He walks with a cane and his leg aches requiring him to take regular exercise in the pool and steam room.