Thankyou very much for taking the trouble to let me know this information! It is very kind of you.
Since I posted my original query, I've made a lot of progress (including much of what you have listed)and in fact, on the strength of what I found, I visited Nevada County in September of 2005. I visited the grave of Judge Snell in Nevada City, and, best of all, I was able to trace his descendant family and met many of them in San Francisco. Magic!
For your information, "W.N 'Billie' Snell" shown in your data died earlier this year, in April. "May Snell", also listed as one of the Judge's children, is still alive and well at 94 years of age.