another Nemo tunnel view i have found.
(https://www.jreb.org/ns/proxy.php?request=http%3A%2F%2Fmembers.trainorders.com%2Fdebutts%2Fsr3135nemo.jpg&hash=e6432d5a3c3283576fa4dce1c05046271aafdaf4)
Cool shot!
Nice photo!
It is interesting, as the tunnel face looks pretty clean in this view. More recent pics of that same portal have a lot of soot built-up right above the entrance. That either means today's diesels burn "dirtier" or that this photo was taken after a storm (when the rain cleared off the southern exposure into the mountain). My guess is the traffic is heavier these days, and more powerful locomotives means more smoke.
RDS