The Nitroglycerin Charge: Tunnel Explosion That Killed Workers on the Transcontinental Railroad
February 1867. Donner Pass, Sierra Nevada. Seven thousand feet. A three-man crew is drilling by candlelight into some of the hardest granite on the North American continent. When the hole is ready, someone will walk three hundred yards to a shed and return carrying a fifty-pound tin of nitroglycerin — brewed fresh that morning by one man in a kettle, costing seventy-five cents a pound to make. The men carrying it were paid a dollar a day.
Nitroglycerin is not a fuse explosive. It is a contact explosive. There is no burning fuse. There is no sequence you can see and run from. There is only physics, and the threshold is so low — a stumble on wet granite, a drill bit striking a residue pocket in a bore hole that was supposed to be empty — that the men working with it had no reliable way to know where it was. With black powder, a misfire left evidence. Smoke. An extinguished fuse. A language of failure you could read. A nitroglycerin misfire was invisible. The bore hole after a failed shot looked exactly like a bore hole that had not yet been charged. The worker who returned to inspect it with a fresh drill bit was completing the detonation with his own hands, twelve inches away, by candlelight.
Three explosions in seventeen days had preceded the decision to use this compound — fifty dead in Panama, fifteen dead in San Francisco, six dead on the Central Pacific line itself. All reported in newspapers the men making decisions were reading. California passed a law banning the transportation of liquid nitroglycerin within the state. The railroad's response was to hire a chemist to manufacture it on-site and route around the law entirely. The productivity numbers were immediate and undeniable. The men absorbing the risk had no voice in the calculation. When they went on strike to demand equal wages and shorter hours, the railroad cut off their food supply until they returned.
Engineer John Gillis, who oversaw the work, later published that he recalled only two accidents in the tunnels. An unnamed colleague remembered it differently: many an honest John went to China feet first. One account appeared in a published journal. One did not. The gap between them is still open.
This documentary tells the story of the Summit Tunnel — the engineering achievement and what it cost to achieve it.
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