Thank you Keith for posting the comments on Nathan B Roberts. I'm very sorry for the late response but somehow I missed your post. I was surfing again tonight and came across it. I have a couple of newspaper articles from local papers the local museum were able to direct me to with similar information to the article you provided.
Since posting I've made contact with living relatives of Nathan's son-in-law, Alexander Denisten McCoul who resided in Wyoming and have been fortunate enough to visit with them in May of 2015. Unfortunatley they didn't have a lot of information on the senior ancestors because of the drowning and family separations which ensued.
Also thank you for the information on the possible surname of Brown. Abigali Roberts was supposedly married prior to marrying Alexander McCoul. I am actually researching the McCoul line and was hoping a lead through the Roberts family might lead to finding the surviving children of the drowning accident, especially Elsie, Nellie and Anna.
Thanks again for taking the time to respond to my query,