Barack Obama took his place as the 44th president of the United States under a bright January sky yesterday, painting the dark national moment in unsparing terms and exhorting Americans to respond by taking greater responsibility for themselves, the country and the world.

Standing on the West Front of the Capitol as the first African-American sworn in as president, Obama celebrated that historic achievement, noting that his ascendance symbolized "who we are and how far we have traveled."

But the heart of Obama's first address to the nation as its president was a stern rejection of the policies and values of his immediate predecessors and a somber call for the return of what he called traditional American virtues of hard work, fair play, tolerance and sacrifice for the common good.

The nation faces "gathering clouds and raging storms" in the economy and in foreign policy, he said, and must respond with the resolve of its ancestors.

"At these moments, America has carried on not simply because of the skill or vision of those in high office, but because we the people have remained faithful to the ideals of our forebears and true to our founding documents," Obama said.

"So it has been. So it must be with this generation of Americans."

Evoking the names and values of the Founding Fathers is commonplace in presidential speeches, but in Obama's case the device seemed intended to make a larger point:

The change he hopes to bring about will require even his supporters to accept things they don't want to accept, work with opponents they've long demonized and break long-ingrained lifestyles.

Americans as a whole must adopt a new, more self-denying way of life with little room for "those who prefer leisure over work, or seek only the pleasures of riches and fame" he said.

In a passage that echoed Franklin D. Roosevelt's first inaugural, Obama said, "Our workers are no less productive than when this crisis began. Our minds are no less inventive, our goods and services no less needed than they were last week or last month or last year. Our capacity remains undiminished.

"But our time of standing pat, of protecting narrow interests and putting off unpleasant decisions - that time has surely passed. Starting today, we must pick ourselves up, dust ourselves off and begin again the work of remaking America."

If the speech was exceptionally somber and included relatively few lines designed to draw roars of approval from the enormous crowd, the day nonetheless resounded with jubilation.

More than a million people flocked to the National Mall to take part in the event, spilling outward from the Capitol steps toward the Washington Monument and the Lincoln Memorial more than a mile away.

Choirs sang. Some of the world's finest musicians performed, including classical violinist Yitzak Perlman and cellist Yo Yo Ma, along with Anthony McGill, a new Peabody Conservatory faculty member, and soul singer Aretha Franklin. High school bands paraded. And tears streamed down faces, weathered and smooth alike, here and around the globe, as the son of a white American and a black African immigrant ascended to his place in history.

The only shadow on the day was cast during the luncheon for the new president hosted in the Capitol by House and Senate leaders: Sen. Edward M. Kennedy suffered a seizure and was taken to a hospital.

The Massachusetts Democrat suffers from brain cancer, but an aide said he was awake, talking with family members and feeling well.

Sen. Robert C. Byrd of West Virginia, the oldest member of the Senate, was sitting near Kennedy and became visibly upset. He was taken from the lunch but is fine, according to an aide.

Former President George W. Bush and his wife, Laura, were whisked away by helicopter immediately after the inaugural ceremony and headed for their home state of Texas after a private farewell to staff at Andrews Air Force Base.

And almost at once, the wheels of the new administration began to turn.