I am descended from the Hatfield line your letter lists.
My 3rd great grandfather was Samuel Hatfield, b. 1797. If you are from this line, I'd be happy to hear from you. I have lots of information on the my Hatfield line, but have seen much conflicting information on some of them. One point sticks out - - the letter says Mathias was of Scotch-Irish descent. I'd never seen that before. The only thing documented that I've come across says he was from Danzig.