Its cargo holds brimming with goods and barrels of money, the side-wheel steamship Republic departed New York harbour in October 1865 on its fifth round-trip journey bound for New Orleans to help refuel the city's post-Civil War economy.
As the vessel steamed down the Atlantic seaboard with some 80 passengers and crew, it encountered rising seas and gusty winds. By the morning of October 24th, the weather had become "a perfect hurricane."
Walls of water smashed into the ship, her boilers failed and her paddlewheels stopped turning. When the auxiliary pump finally quit, water filled the entire lower deck.
Passengers and crew abandoned ship in four lifeboats and a make-shift raft. Within moments the ship disappeared beneath the waves and sank 518 meters into the dark, cold Atlantic. The last location of the side-wheel steamship was a mystery, her cargo believed lost forever.
Yet, 138 years later in 2003, Odyssey Marine Exploration, pioneers in deep-sea shipwreck exploration, discovered a promising target on the seafloor. It was 100 miles off the Georgia coast and one-third of a mile deep - far beyond the reach of human divers.
Lowered by crane from the surface vessel Odyssey Explorer, the company's 8-ton remotely operated vehicle (ROV) nicknamed ZEUS, cautiously approached the wreck site on the ocean floor, its powerful lights illuminating the ghostly remains of a side-wheel steamship sitting upright on the seabed.
Much of the ship's hull had collapsed, leaving piles of shattered timbers. Its two 28-foot diameter paddlewheels and vertical walking beam engine, standing 13 feet high, had remained surprisingly intact.
Spilling out of the cargo holds was an amazing plethora of artifacts - heaps of white ironstone china, bolts of cloth and a stockpile of patent medicines to cure every ailment known to mankind; an extraordinary 19th century time capsule offering a rare and fascinating window on life in mid-Victorian America.
Among the more intriguing items observed on the seabed were deposits of writing slates, some in a jumbled heap, revealing the chaos that must have occurred as the embattled ship sank hundreds of meters to the ocean bottom.
Yet oddly, other slates at the site were standing upright on their sides in perfectly uniform rows, as they had originally been packed in their wooden shipping crates, now eroding in the harsh Gulf Stream. Missing were the narrow wooden borders framing the rectangular slates, typical of transatlantic slate cargo stowage.
The slate cargo observed on the seabed was picked up one-by-one by ZEUS' limpet suction device and carefully brought to the surface in a metal container designed to endure hundreds of meters of pressure.
Safely aboard the Odyssey Explorer, the new life of the writing slates began to unfold as research shed light on their origins across the Atlantic, where the slate was mined and turned into writing tablets prior to transport to America.
The distinctive blue-grey coloring of the slate would later confirm it being of the variety known as "Old Vein", mined in Blaenau Ffestiniog.
From here, the slate would ultimately reach Porthmadog. By 1865 the railway between Blaenau Ffestiniog and Porthmadog was transporting 100,000 tons of slate annually.
Beginning in the early years of the American colonies, nearly all slate was imported from North Wales, shipped as saleable ballast cargo.
Many US port cities feature homes with mansard roofs made from Welsh slate installed well before the emergence of the American slate roofing industry.
While the Republic slates, with polished surface honed for writing, were clearly not intended for roofing, it is quite probable that they too, were shipped across the Atlantic as ballast cargo.
In the absence of a cargo manifest, the intended recipients of the slate will remain a mystery. However, while paper had become commonplace by the late 1800s, at the turn of the century, slates were still widely used as writing tablets in the schools.
It is not unreasonable then to assume that the Republic's slate cargo bound for New Orleans was intended for use in one of the many public, private, or religious schools in the city and in the surrounding parishes, including those established for the former slave population.
From distant origins in tranquil Blaenau Ffestiniog, through the horror of a hurricane, a dramatic shipwreck, and an equally astounding discovery using futuristic robotics, an obscure slate cargo lost deep in the Western Atlantic, has resurfaced over a century later to tell its story.
By Ellen Gerth and Hawk Tolson, with thanks to Dr Dafydd Roberts, Keeper, National Slate Museum, and Steffan ab Owain, Gwynedd Archives. A longer version of this article was published in the journal North South Trader's Civil War.
