We rode last night on a real train. It caught fire briefly and once it came close to derailing, if you want to nitpick. But how glorious.

The John Bull is the world's oldest locomotive that still can be made to run, and it gives you a sweet ride at least the equal of the Metroliner and moreover it can be made to run on schedule.

For almost a century now the John Bull has sat in the Smithsonian Institution's care (now at the Museum of American History) and until last night it had not been allowed out on its own power for more than half a century.

But it was built in 1831 and started running madly on the Camden and Amboy line in New Jersey in 1833, though it was superseded by the 1850s as fancier engines came off the drawing boards.

Its run last night celebrated its sesquicentennial. Mainly its run last night celebrated John H. White Jr.'s pipe dream. He is the Smithsonian's curator of transportation. He has always secetly been on fire to steam up old John Bull, but of course knew it was impossible.

"Why is it impossible?" asked the museum's director, Roger Kennedy.

Say no more. White began the little two-year process that led at last to an active run on a real track, with real oak burning in the boiler and the brass bell ringing like mad and all the backed-up rush-hour traffic trying to get to Chain Bridge dropping teeth with astonishment as above the stalled cars the noble old engine puffed and showered sparks and clattered like a chatty miracle across the steel bridge high above Canal Road.

Sen. Howard Baker (R-Tenn.) was reported halfway between a frenzy and a lather as he photographed it. Any Tennessean would regard this ancient engine as the greatest thing since hush-puppies.

The old engine was tested in Virginia last fall, way out in the country. It ran through a few towns with names like Cornucopia and everybody turned out to see it. A Smithsonian source said those towns hadn't seen a train for years (thanks to the general disintegration and collapse of the nation's once-magnificent rail system) and a lot of people didn't know the John Bull was a museum piece. They just figured the trains were running again.

The locomotive will run again today, 11 to 3, from Fletcher's Landing (Reservoir and Canal Roads), with bands playing and balladeers singing and an old telegraph station operating. A fellow will make apple cider. Some folk will ride high-wheel cycles. Along the canal people will be shooting their amateur candid shots as the proud iron horse races back and forth between Key and Chain Bridges at dizzying speeds of around 15 miles an hour.

Unfortunately, you can't ride behind it today.

White says never again, never again in his lifetime will the old John Bull run. It is, after all, 150 years old and no point testing its old plates to the breaking point.

Last night they hitched up an 1836 passenger coach to it and filled it up with invited guests. Rep. Christopher Smith (R-N.J.) was an early arrival. He is only 28 years old and can bound up to the tender platform without thinking twice.

Between the engine and the passenger coach was the tender, a wheeled platform that holds firewood for the boiler and has a great lever sticking up, said to be the "brake." (The old locomotives had no brakes. Macho enginners wanted to go, not to stop. Theoretically if you brake the tender the locomotive stops. White has written a marvelous small book full of technical notes about the John Bull, but even the layman can learn there that the locomotive came without any brakes.) There is also a great oak water butt and a tin cup to dip it out with.

A member of the press was installed on the tender, presumably to absorb all the sparks from the smokestack. These sparks were very pretty. (The smokestack has been on the engine for a century but it is absurd. It was installed for the 1876 Centennial Exposition in Philadelphia. They thought the original smokestack looked too modern, so they dreamed up the present smokestack, but no train ever ran seriously on its workaday schedule with a stack like that).

Some of these sparks lodged in a crevice of the passenger coach roof.

Innocent ladies were inside. You could see Judith Huxley, for instance, smiling sweetly as she peered out the window at the canal. Little did she or the other passengers know smoke was coming out the roof of their car.

The press, responsible as always, declined to scream FIRE. There is such a thing as being truthful once too often.

The brakeman, Robert M. Vogel, is one of those learned authorities at the Smithsonian but he was done up in an ancient railroad man's costume and from time to time he leaped from the tender to the coach. He gave the impression he operated the old line to Tombstone and Flagstaff singlehanded. He possibly hoped nobody would know he was a scholarly fellow at the Smithsonian. Very rugged, very macho. And a hero, too. When the fire started he raced for the water butt, dipped out a swig of water, lept toward the roof of the coach and spat it out. He repeated this heroic process (the press in its general snoopery had already peered into the water butt before the train started and noticed a number of pitiful bugs drowned dead floating about and decided against trying out the tin cup, therefore) until no trace of smoke remained. All this time the train was running. Thanks to steel nerves of men on the tender nobody panicked.

The train got up to about 30 miles an hour. This is a speed sufficient to lift the ears of a hound horizontal if it has its head out the window.

A fellow from the press rang the brass bell coming and going. It is work to run a train. Once a tree branch was spotted on the track. John Stine and John White cried for brakes to be applied at the far end of the coach. Possibly the ringing bell and the hissing steam and the old cast-iron wheels prevented the message carrying.

"We get no response," said Stine. Later, he said "We got no response." Stine is also at the Smithsonian. A man of temperate calmness in an emergency. If you're going to ride around with brakeless locomotives, Stine is a good man to have. The train stopped just short of the fallen branch. White said it might not have derailed the train. But then again it very well might have. The press did its duty and rang the bell through it all.

This reassured passengers. Prevented a stampede and saved many lives, it was thought. But the nation is full of heroes who ask no reward. It is mentioned only to show that ordinary men rise to heights when necessary.

A little coal-oil burned in the train's headlight. Joggers trotted along the canal lost in wonder. Fuzzy dogs along the canal looked up. Back at Fletcher's Landing there was a tent with little tables and candles. They had orange juice and (for the luxuriant and abandoned) cold wine.

"I am famished," said Robin Jacobsen, whose architect husband is off on a jury but who made the journey alone, as pioneer women often did. She ate patty shells stuffed with chopped oysters in a sort of Coquilles St. Jacques sauce. She was brave all the way. America is full of women who without ado can get places on their own and manage quite well, thank you.

It is hard to think that after today the old John Bull will probably never again run free under the sky, merrily catching fire and racing up to fallen branches and amazing rush-hour automobile traffic. But there comes a time to cease the mad rush. There is a pasture-time for all.