You are in the CarrTracks website Picture Gallery.
A Union Pacific passenger train (I think this might be Number 9 the City of St. Louis) is dropping down the hill at what used to be called "Drawbar Flats." Before the second main was added uphill trains faced a stiff three percent grade from Cajon station up to Summit. Many trains pulled drawbars or busted knuckles in this area. If you look to the left you can see an eastbound UP train climbing the hill by the Morman Rocks.
Jack's train is slowly descending the three percent grade toward Cajon station. The train will stop there to cool the wheels.