got an answer from a very helpful person - thanks!!!
"""" Bruin Path, from near Bruin Rock up to "Scaur Path" and then to Air Line was scouted in 1882 by Cook & Watson, and was finished by 1883 & measured by Pychowskas. This was the continuation of Watson's Madison Path which went as far as Salmacis Fall in 1878, and continued in 1882 with a split into a path up Madison (today's Watson Path) and a path up Adams. The upper section of the old Bruin was no longer there in the AMC 1916 guide.
As far as I know, today's Lower Bruin continues on much the same track, but the continuation to the w of Valley Way became overgrown and disappeared.
Today's Upper Bruin is reported as a "new crosspath" in 1900, [this would lead me to believe that the original Bruin might have been in disrepair by then] which creates a graded path with 3 mi of smooth walking on the Valley Way and the Knife Edge. It was accepted by AMC in 1913, and in 1918 became RMC in exchange for the RMC's Arethusa Falls Trail"""""
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