Washington was a walking contradiction yesterday.

In the midst of the Labor Day weekend, marking the unofficial end of summer, tourists thronged to the museums along the Mall.

But with breezy, cloudy weather, there were signs of a slowdown.

"It's very quiet," reported Heidi Doyle, a National Park Service technician at the C&O Canal in Georgetown. Seats on The Georgetowner, a canal boat replica that can hold 70 persons and is usually full, were going begging.

Doyle said the 1 p.m. run, normally a sellout, had 35 empty seats. "It's very, very slow today," she said.

At the Old Stone House, also in Georgetown, Park Service site manager Rae Koch said 192 people had trooped through by midafternoon, far below normal for a Saturday at the 220-year-old building.

On Friday, only 149 came, half the number usually touring the structure that is said to be Washington's oldest building.

"It's deserted; ain't nothing happening," said a U.S. Park Police dispatcher. "Everybody must've packed up, backed up or left town.

National Airport was virtually empty, too, according to Ray Frankenberg, the Federal Aviation Administration operations officer there. "It's like 10 o'clock on a Saturday night," Frankenberg said yesterday afternoon. "It's ridiculous. I should be out playing golf."

Even Friday's expected rush did not materialize. "We had airlines canceling flights." he said. "Either people are staying home or they left Wednesday."

At Gusti's restaurant, a fixture at 19th and M streets NW, business was slow all week, according to cashier-hostess Wendy Wood.

"We usually do a brisk lunch business," she said. "It's way off this week. You just don't see the crowds like you usually do."

On a normal Saturday, Wood said, 20 tables are occupied through lunch. Yesterday, she counted six. And the restaurant's sidewalk cafe was "not even half full, which is unusual for a Saturday afternoon," she said.

But Washington was not exactly a ghost town: Parking spaces were scarce along the Mall, and sidewalks in front of the Smithsonian Institution were thick with people.

"It's always busy," said Divine Sewornu, assistant manager of the National Air and Space Museum Shop. "It's like a usual Saturday," said Djamal Balded, manager of the Arts and Industries building store.

And at the Washington Monument, there was a definite, if modest, line of sightseers waiting to ascend the tower.

As for the Capitol, "It's never deserted," Capitol Police Inspector Roy Bell said. "It's just less cluttered."