This discussion on Lassen is the best I've ever seen on the OT list--I especially appreciate Don Buck's excellent analysis of this tricky history.

In looking again at some of the sources, I found this description of the Mormon Battalion's encounter with Lassen's westbound train:

Rogers, Samuel Hollister. The 1848 Trail Journal of Samuel Hollister Rogers. Ed. by Will Bagley. Salt Lake City: The Prairie Dog Press, 1991.

Sa 26 [August 1848] We started as usual but had not gone far when we met 10 wagons from the states. they came by way of Salt Lake. A man by the name of Levi E. Riter was with them from Salt Lake. he told us that he was a Bishop of one of the wards. We then traveled some fa[r]ther, crost the river. in a few miles after we camped, it being 20 miles in all.

Rogers's intriguing entry says nothing about how Lassen got from Salt Lake to the Humboldt, but this information raises the possibility that it was Lassen and his wagons, not Samuel Hensley, who opened the Salt Lake Cutoff.

Will Bagley