"We know Washington paid 10 shillings for the lock on the door to the granary in the cellar," Mr. Ridout says. "We know the superintendent was a white carpenter named Thomas Green, who worked for Washington on an annual contract. He was missing two fingers from a saw accident and liked to drink. He was known occasionally to have lost weekends in Alexandria."
Planning the reconstruction, a team of a half-dozen historians, archaeologists and architects met regularly for nearly two years beginning in fall 1992. They vowed to use the same materials and techniques Washington used -- as long as it was feasible.
"In other words," says John O'Rourke, the project's construction manager and a carpenter from Solomons Island in Calvert
County, "everything you see will look exactly as it was. If it doesn't show, we'll cut as many corners as we can to try to save money."
Nothing was assumed.
"We started at the bottom of the building and worked our way up," Mr. Ridout says. "We spent an entire day on the brick foundation. What kind of brick? What bonding pattern? What was the mortar mix? The joint finishes? Was it white-washed? How was the interior finished? . . .
"Then we moved on to the interior of the first floor. How was it framed? Was it pine or oak? . . . We could answer most of those questions."
But knowing so much created its own problems.
The researchers knew from records that for the barn's frame Washington ordered Southern yellow pine cut to size from near Salisbury on Maryland's Eastern Shore. But he forgot to order eight 12-by-12-inch posts for the granary level of the barn. His slave carpenters cut those from white oak at Mount Vernon.
Mr. Ridout, whose specialty is 18th- and early 19th-century Chesapeake architecture, knew that most Eastern Shore timber from that period was hand-sawed. To double-check, he and the other researchers spent a day in Alexandria, nine miles north of Mount Vernon, examining timber in buildings constructed in the 1790s. They assumed that builders in Alexandria had the same timber sources as Washington. And they found nearly all the timber was hand-sawed.
Construction began last fall near the wharf on the river, a 10-minute walk from the mansion. That is not where the barn stood 200 years ago. Mount Vernon in Washington's day was 8,000 acres. It now is about 500 acres. A housing development sprouted on the original site in the 1950s.
The project will cost about $3 million. The W. K. Kellogg Foundation donated $2.25 million with the rest coming from private donations.
Mr. O'Rourke's craftsmen already have built the first-floor brick wall. They're preparing beams and joints for the interior and second floor with pit saws, handsaws, broadaxes, mallets, chisels and other 18th-century tools. By the time they finish next summer, their reconstruction will blend with modern adaptations such as steel pilings and a wheelchair lift.
And then, the ultimate question can be answered: Did the barn work?
Mount Vernon officials are planning threshing demonstrations inside the barn -- their experiments on Washington's experiment. They're even training horses to walk in circles on slatted floors.
"In theory, it should have worked," Mr. Ridout says. "But Washington writes endlessly about building it, and almost nothing about using it.
"The best indication is he wasn't thrilled with the result. Even as he developed this new technology, it was being bypassed by the new small threshing machines from England. Washington probably found his solution, but he found it 10 years too late."