There are dates for a John Scott (1802-1885) who may have been the artist who painted the 19th century image of Lanyon Cromlech near Penzance. However that John Scott was born and died in South Shields, and worked there most of his life. He was known as a landscape and marine painter who specialised in sailing ships. However he may also have sailed in these and painted on lands where he stepped ashore. Lanyon Quoit is the name of this assemblage of stones in the present day, and the relative formality of the title given to the painting indicates this John Scott was probably a visitor.
Nevertheless, this is only conjecture, as the painting as seen gives no other clues except the signature and title written verso. Alternatively the artist may have been a talented amateur with that fairly common name.