Who is Josiah Gorton from The Moor: A Mary Russell Novel and what is their importance?

Josiah Gorton is a tin miner. He was discovered on the moor under suspicious circumstances and died shortly after. Josiah talked about having been taken for a ride in Lady Howard's hearse, as well as the presence of a ghostly hound. Holmes re-enacts Gorton's movements before his death and finds a small bottle containing what turns out to be gold flakes.