Image copyright Smithsonian Institution/Ken Rahaim

The world's largest museum and research organisation is celebrating the 250th anniversary of the birth of its founder. But it was pure luck that the Smithsonian Institution was ever created.

Inside a small crypt near the entrance of the Smithsonian castle on Washington's National Mall is a memorial to James Smithson, an English scientist who is roundly praised for never having fathered any children.

If he had, his vast fortune would not have been given to America to found the research organisation that bears his name - the Smithsonian Institution.

His nephew should also share some of the credit as Smithson's wealth initially passed to him. But he too died childless and thanks to a clause in Smithson's will, the money was bequeathed to the US to establish an organisation "for the increase and diffusion of knowledge among men".

That two wealthy men should leave no heirs is perhaps the first stroke of luck that led to the creation of the Smithsonian, and there is much scholarly speculation as to how this happened.

Pamela Henson, the Institution's historian, says it was partly because Smithson was illegitimate. Although he was recognised by his family and inherited lots of money, he was unable to marry a woman of any social status. She also says he may have been gay. But neither explains how he must have guessed that his teenage nephew would also die without children.

Image copyright Smithsonian Institution Archives Image caption The monument of James Smithson in the Protestant or English cemetery in Italy

"And we will probably never know, because all of James Smithson's papers were burned in a fire at the castle in 1865," she says.

Getting the money out of England was also an ordeal, compounded by lingering animosity over the War of 1812. British troops had invaded Washington and burned much of the city including the White House. Lawmakers weren't certain they wanted cash from a foreigner - especially cash belonging to an Englishman.

But in 1836 the American lawyer Richard Rush was sent to England (after posting a bond of $500,000 to make sure he didn't run off with the funds) to pursue the claim in the infamous British Court of Chancery. Cases could take hundreds of years and the court's corruption was so notorious that Charles Dickens wrote his novel Bleak House about it.

In nothing short of a miracle, Smithson's will was settled in just two years and the money was ready to be delivered to the US - but how?

Rush converted Smithson's investments into 104,960 gold sovereigns, eight shillings and seven pence, secured it in 11 boxes and accompanied it onboard the Mediator. The transatlantic crossing took six weeks and was beset by storms, any one of which could have sent Smithson's fortune to the bottom of the ocean.

When it arrived, the gold was melted and turned into US coins worth $508,318 and 46 cents.

Image copyright Smithsonian Institution

Not unreasonably, Rush asked the administration for time off to recover from his endeavours. "Somewhat worn down by fatigue since coming on shore, after an uncomfortable voyage of squalls, gales and headwinds, I venture to ask a little repose at my home before proceeding to Washington," he wrote.

The money was safe, but it still took Congress several more years to pass the Act to Establish the Smithsonian Institution which became law in 1846.

But that was not the end of the story for James Smithson himself. He died in 1829 without ever visiting the US, and in 1903, Alexander Graham Bell, the inventor of the telephone and one of the Smithsonian's regents, decided to put that right.

In the middle of winter Bell and his wife travelled to Italy to have Smithson's body exhumed from a cemetery in Genoa. The weather was bad, but that didn't stop Mrs Bell from taking photographs of the grisly process, including an image of Smithson's skull being held aloft by the US Consul William Henry Bishop.

Image copyright Smithsonian Institution Image caption US Consul to Genoa, William Henry Bishop, holding Smithson's skull during exhumation

Eventually Smithson's remains were sealed in a casket and shipped to the US, arriving on 7 January 1904. After a procession to the castle, the coffin was placed in an upstairs meeting room where it stayed for a year while the Smithsonian Board of Regents decided what to do next.

"There were a few rough sketches for memorials, but the plans would have dwarfed the Lincoln memorial," says Richard Stamm, the castle curator. "And as it became apparent that less and less money was available, the plans became smaller and more modest."

Image copyright Smithsonian Institution Archives Image caption The steamship Princess Irene sailed from Italy to New York, carrying Smithsonian Regent Alexander Graham Bell and his wife Mabel and James Smithson's remains.

In the end, the janitor's closet was converted into the crypt where Smithson rests today.

"That was the first indignity we've foisted on James Smithson since he came to this country," says Stamm. A second was to follow.

In 1973, while the Secretary of the Smithsonian was out of town, Stamm's predecessor, James Goode, decided to have the body exhumed because he had heard ghost stories.

"People were saying they'd seen Smithson roaming the office," Stamm says.

Workmen opened up the end of the panel under the memorial and removed the coffin. Inside they discovered a metal casket that was soldered shut. Goode told them to use their torches to open it, but the coffin's silk lining caught fire.

"He didn't want them to ruin the silk by using an extinguisher so he told them to fill their mouths with water and come back to spray it down. So they did it."

The metal casket contained bones and dirt from the original gravesite and was taken across the road to the Smithsonian's National Museum of Natural History for tests. Smithson was then reinterred with a full lab report of the findings.

Image copyright Smithsonian Institution Image caption A view of the national mall, lined by many of the Smithsonian museums

"The pathologist recorded that he had nice, young bones and no arthritis. Even though Smithson complained throughout his life of being chronically ill he was actually in pretty good shape when he died," says Stamm.

There are no further plans to exhume or move James Smithson. Visitors can pay their respects at the Smithsonian Castle which he is still said to haunt. The last documented appearance was during a seance in the building during the 1980s.

But Stamm is adamant that after four decades he has never seen a ghost, of James Smithson or anybody else. "I've been in the building for 39 years and I've never seen a thing," he says.