On an otherwise unremarkable spring day, as his under-supplied and dispirited Continental Army prepared to stave off a Redcoat advance on New Jersey, Gen. George Washington noted a strange weather phenomenon in his diary: "Heavy & uncommon kind of Clouds -- dark & at the same time a bright and reddish kind of light intermixed with them -- brightning & darkning alternately. This continued till afternoon when the sun began to appear."
Further to the north, observers told of much more alarming conditions. In the skies above New England, their diaries and letters recorded, the sun failed to appear at all.
Welcome to "New England's Darkest Day," May 19, 1780, a 24-hour period during which residents ate meals by candlelight, reported night birds singing at noon, saw flowers folding up their petals, and observed strange behavior from both beasts and men. So profound was the gloom that at midday, wrote Harvard professor Samuel Williams, "persons could not see to read common print in the open air." At sundown, no moon or stars appeared.
In Hartford, Conn., representatives of the state legislature feared the end of the world was at hand. Some, quite sensibly, urged adjournment.
"The day of judgement is either approaching, or it is not,' said their colleague Col. Abraham Davenport. "If it is not, there is no cause of an adjournment; if it is, I choose to be found doing my duty." The session continued. So, thankfully, did the world.
For years afterward, according to Erin McMurry, a research assistant in MU's Tree Ring Laboratory and Richard Guyette, MU professor of forestry and the Tree Ring Lab's director, the cause of the curious darkness remained a mystery. No longer. In a new finding the two College of Agriculture, Food and Natural Resources scholars have coupled contemporary accounts of the event with evidence from "fire scars" on trees to determine that the dark day was almost certainly caused by smoke from Canadian wildfires. The study, Fire Scars Reveal Source of New England's 1780 Dark Day, was published earlier this year by the International Journal of Wildland Fire.
Hints that smoke played a role had long been part of the lore surrounding the event, the researchers found. Harvard's Williamson, for example, wrote that a "thick and dark and sooty," rain fell in the darkness, one that smelled of "black ash and burnt leaves." The MU team followed up on such observances by examining tree rings from the Algonquin Highlands of southern Ontario and other locations in the region.
"We think of tree rings as ecological artifacts," says McMurry. "We know how to date the rings and create a chronology, so we can tell when there has been a fire or a drought has occurred."
The trees in Ontario and elsewhere pointed to a huge fire in 1780, a conflagration so intense that it carried columns of smoke well into the upper atmosphere. Such an inferno would have affected conditions hundred of miles away, the researchers say, even blocking out the sun in some locales.
"A fire comes along and heat goes through the bark, killing the living tissue. A couple of years later, the bark falls off revealing the wood and an injury to the tree. When looking at the rings, you see charcoal formation on the outside and a resin formation on the top that creates a dark spot," Guyette says -- a dark spot illuminating a dark mystery New Englanders can, 228 years later, finally put to rest.