I'm a descendent of a Charles B. Maxwell from Boston.  His civil war diary was handed down through my family.  It can be found online here: http://www.blurb.com/books/2374573. In the diary, there is an invitation to a reunion of the Nim's battery in 1890 after the civil war ended.  The invitation says it was prepared by Mrs. Chas B. Maxwell.  I wonder if this was Ellen.  If so, I would guess this your great, great, grandfather's diary as well. I live in Hanson, MA.