Mid 1800's 10 x 12 Painting of Volcano (Mt. Vesuvius?)

I found this painting in the bottom of a bin at the goodwill in Southaven, MS. (laugh if you want,but I have many treasure worth something from there) plus the hunt is fun. It caught my eye and it was .59 so I could not go wrong. It looks like a Mt. Vesuvius painting? and it fits that time frame. Sotheby's said it is not an Aaron Shattuck painting and they were unable to authenticate at this time without the painting? and the Dixon Art Gallery said my dates seem good the wedge canvas clips date 1883 ADS but it is not his work? So here I am I know this is going to take some research and I have done a lot already. It does have a signature but I cannot make it out? It could be a PO19 or a DU19 or Don...This is all I can make out on the bottom right with a magnifier. I am sure if I choose to restore and have it cleaned we will be able to read the signature. This will be a challenge.