Gallup, N. M., Troops guard mines as riots threaten in bitter strike fight, military guard a building, martial law, police inspections, confrontation, St. Paul, MN., 70,000 see locomotives in head-on collision at spectacular show, long shot of moving train called the N.R.A collides with another train called Old Man Depression, close up of tracks, crash causes explosion, derailment of both trains and lots of smoke,