Hi Clyde, That sort of information you'd find in a write up about the family. I don't know if you'd ever be able to prove it.
However, his family tree was published by pawstreet on www.ancestry.com. You can go to Ancestry, click on Family Trees and enter his info even if you're not a member and you can connect with pawstreet.
I had a situation like that where my grandfather herded cattle for Portugee Joe in the Moses Coulee (Washington). I wrote it up with the source being my mother. Imagine my surprize when I read in a historical book that Portugee Joe did have cattle herds during the correct time frame in the Moses Coulee which I added to my family info.
I'd look for historical books on Linn and Lane counties especially since he was living there at such an early date. Google Book is a good search engine for these books. Sometimes you can read them on-line and generally you can request them from your local library via inter-library loan at no charge.
I'd also check with these genealogy societies since they might have books or documents about James. Oregon Genealogical Society and Research Library, www.rootsweb.ancestry.com/~orlncogs/ogsinfo.htm .