This pic really shows the roller coaster profile between Durango and Gato. Once over the top of the 2% grade out of the Animas Valley at Falfa, They dropped down 1.42% off Florida Mesa to cross the Florida River, at (you guessed it..) Florida, then they climbed out of the Florida watershed on 1.42% and dropped down the same gradient into Oxford in the little valley formed by Salt Creek, which flows into the Florida down south. From Oxford the climbed up another 1.42 grade over the divide then down into the Los Pinos (Pine) River valley at Ignacio. They followed the Pine River south to La Boca, crossed it and headed up Spring Creek on yet another 1.42% grade to Tiffany, where they began a long decent to the San Juan River west of Arboles. From there it was essentially up grade all the way to Chama on grades ranging from 1.2% to 2.0%.
Oxford was noted as a place where over energetic hogheads liked to kick the air off and let 'em roll down the hill to get a run at the hill going east. Problem was they had trains set up like 497's here with a slug of empties on the head end with loads in the center. They'd rip the throttle wide open with the train still pushing them down from the rear. The slack would come out with those loads anchoring the rear of the train and literally rip an empty wood pipe gon or idler flat in half.
I'd love to have heard what 497 sounded like here. From how she is carrying her exhaust, she really getting after it. The big cloud of smoke tells me the fireman has just given her a slug of coal where she needed it most. The brief clearing of the stack we see just as John tripped the shutter is with the fireman at mid-stroke - the firedoor is open giving the fire a little bit more air to clear the smoke as he flings another scoop it. I bet of John had waited 2 more seconds to trip the shutter, 497 would have erupted another big cloud of smoke.