After 150 years, the explosion at the U.S. Arsenal in Lawrenceville -- among Pittsburgh's worst industrial accidents -- hasn't given up its secrets.
"To this day, the cause of the explosion remains one of the great mysteries of the 19th century," Jim Wudarczyk of the Lawrenceville Historical Society has written. "There were two major inquests into the explosion but neither was definitive in determining the key factor for the deadly blast."
The immediate cause of the blast, which killed 78 people, has been blamed on many things, ranging from sabotage by Confederate agents to the careless handling of gunpowder by workers at the arsenal. Others have pointed to lax enforcement of safety rules by Alexander McBride, the civilian superintendant of operations.
Some have argued that leaky barrels used by E. I. DuPont Co. to ship gunpowder to the arsenal also played a role. They believe that because DuPont was the main supplier of gunpowder to the Union army, the company's culpability in the accident was never fully investigated.
In a modern twist, other researchers have suggested that static electricity from the hoop skirts worn by the young women and girls who worked at the arsenal may have caused a spark that triggered the blast on Sept. 17, 1862.
The explanation that was widely accepted from the start still holds sway, that the scraping of a horse's steel shoe or an iron-rimmed wagon wheel against the stony pavement created a spark that ignited spilled gunpowder in the roadway near the arsenal's laboratory. The blaze from that fire ignited a 100-pound barrel of gunpowder nearby that had recently been delivered to the arsenal's laboratory.
Perhaps part of the appeal of this explanation to those alive in 1862 was their astonishment that a seemingly insignificant act could have such huge repercussions. The Rev. Richard Lea, pastor of nearby Lawrenceville Presbyterian Church, echoed this sentiment when he spoke to his congregation 11 days after the explosion.
"How could those dear girls [who worked at the arsenal] know that by the grinding of a wheel ... such dire calamity could be instantly brought upon thousands," he said.
Two days after the explosion, a six member coroner's jury began its investigation. One of the first witnesses to testify was Joseph Frick, a wagon driver who had delivered three 100-pound barrels of gunpowder to porch No. 1 at the laboratory a short time before the first explosion.
Frick testified that after completing delivering gunpowder to other rooms in the laboratory, he returned to No. 1 to pick up some empty cylinder boxes. Frick said he noticed spilled gunpowder in the road near No. 1, and it wasn't the first time. Four days earlier, Frick said he also had seen spilled gunpowder in the road.
Frick told the jurors that the powder in the road was ignited by the forewheel of his wagon coming into contact with the stones in the road. He saw the powder "fizzing" and then, almost instantly, an open barrel of gunpowder on the porch ignited, knocking him from his wagon.
Another witness, arsenal worker Rachel Dunlap, corroborated part of Frick's story. She was standing in the doorway of a nearby room (No. 12) when she saw "the shadow of a blaze at the forewheel of the wagon, near the hind hoof of the horse." The first explosion knocked her down.
But how reasonable is this explanation for the explosion?
Jimmie Oxley, an expert on explosives and a professor at the University of Rhode Island, believes the account given by Frick and Dunlap "is not unreasonable." Ms. Oxley, who has studied the chemistry of thermal decomposition of highly energetic materials, notes that black gunpowder is a highly sensitive substance. Even today, the storage requirements for black powder are stricter than those for smokeless powder.
She also notes that there were other gunpowder explosions during the 1850s and '60s that were attributed to the scraping of iron horseshoes or wagon wheel rims against stone pavement. One notable incident occurred on May 31, 1854, when three DuPont powder wagons blew up in Wilmington, Del.
In the 1970s, demolition crews tearing down a building at the Picatinny Arsenal in New Jersey triggered a gunpowder explosion. Apparently, small quantities of black powder in the masonry were ignited, Ms. Oxley said.
"There have always been housekeeping issues involved in the manufacture of gunpowder," she said.
That fact was not lost on the coroner's jury nor the military board of inquiry, which also investigated the arsenal explosion in Lawrenceville. Some witnesses claimed that employees often swept powder into the road at the end of a shift-- at least in one instance with the explicit approval of McBride.
Another witness said he often wore boots with two rows of nails in the soles when working in the arsenal's powder magazine, although regulations required that men working there wear moccasins. McBride never warned him of the danger, he claimed.
A contractor who had supplied the stone for the road that ran beside the laboratory told the coroner's jury that he had seen horses at the quarry strike a fire on the same stone that was used to build the road. The coroner's jury may have wondered if this information was ever passed along to Col. John Symington, the arsenal's commander.
On the evening of Sept. 27, the coroner's jury completed its investigation. The panel unanimously concluded that the gross negligence of McBride as well as his assistant, James Thorp, caused the explosion. Four of the jurors, plus the coroner himself, also blamed the explosion on the negligence of Symington and two of his lieutenants -- James Myers and John F. Edie Jr.
Two jurors "utterly and entirely" dissented, saying that the testimony presented the jury "clearly discloses that this sad disaster is to be attributed to the disregard by the superintendents of the wholesome and stringent orders of Col. Symington."
With the coroner's verdict now in, Symington asked his superiors in Washington to appoint a military board of inquiry to examine not only his role in the explosion but also his entire tenure as the arsenal's commanding officer. The three-member military panel met in October and completed its work late in the month. The panel exonerated the colonel and his young lieutenants.
On Nov. 1, 1862, Symington went on sick leave and by July he had retired from the Army. He would die in Maryland on April 4, 1864.
Frank Reeves: 412-263-1565 or firstname.lastname@example.org.