ATLANTA, JUNE 27 -- South African black leader Nelson Mandela laid a wreath of yellow mums at the grave of slain civil rights leader Martin Luther King Jr. today as this southern city where the American civil rights movement was born embraced a new living hero.

In the most symbolic and poignant moment of a visit that has taken him to four U.S. cities, Mandela paused briefly in silence at the marble tomb, then stood shoulder to shoulder with King's widow, Coretta, and other American civil rights leaders as they sang a verse of the movement's anthem, "We Shall Overcome."

Tonight, at a rally attended by 50,000 people, Mandela evoked parts of King's famous "I Have a Dream" speech of 1963, repeating King's words but altering the final phrases to say instead:

"Let freedom ring in South Africa. Let freedom ring wherever peoples' rights are trampled upon. Let freedom ring."

After visiting the gravesite, Mandela and his wife, Winnie, were whisked down Auburn Avenue, where King frequently shopped as a boy, to speak at the Big Bethel A.M.E. Church. He also visited Morehouse College, where he was awarded honorary degrees from 41 historically black colleges and told that 20 four-year scholarships and four two-year scholarships have been established there for South Africans.

People in Atlanta, where King was arrested for attempting to buy lunch in the whites-only Magnolia Room of Rich's department store, said they felt a bond with Mandela in South Africa's struggle for minority rights.

"We welcome you home," Mayor Maynard Jackson told Mandela in an airport welcoming ceremony. Everywhere, that mood was obvious.

The inevitable comparisons to King were made. Andrew Young, one of King's chief lieutenants who became a member of Congress, U.N. ambassador, mayor of Atlanta and is a candidate to become the first black governor of a Deep South state, said Mandela and King were "children of the middle class" who "could have escaped and taken care of themselves, but they devoted their lives to the cause."

At the airport, Mandela himself pointed out the sharpest distinction. Whereas King preached nonviolence to his followers in their struggle to win voting rights and end segregation, Mandela reiterated his position that violence has a place in his own struggle. "Nonviolence is a good policy when the conditions permit," he said. "But there may be cases where the conditions do not permit."

Mandela drew parallels between South African blacks and blacks in the American South. "The weather, the landscape, the warmth of the people evoke memories for us of home," he said. "But unlike you, we are still under the grips of white supremacy."

He made a pointed reference to continuing racial tension in this country, saying, "When we landed here, one of the issues that struck us was the fact that we are in the home of liberty, equality and fraternity -- at least in law, if not in practice."

About 50,000 people paid $5 each to attend tonight's rally at Grant Field, the Georgia Tech football stadium. Unlike the spirited and sometimes raucous outdoor gatherings for Mandela in New York's Yankee Stadium and along Boston's Esplanade, the crowd here seemed more relaxed.

The celebratory aspect of Mandela's tour, suspended during the somber observances earlier today, resumed abruptly as trumpeter Hugh Masekela, an exiled black South African, began a rousing version of his popular song, "Bring Back Nelson Mandela."

Mandela told the crowd that, during his imprisonment that began in 1963, he was aware of King's struggles. "In our prison cells," he said, "we felt a kinship and affinity with him and were inspired by his indomitable fighting spirit."

After the rally, Mandela flew to Miami, where city officials were preparing to greet him as coolly as officials greeted him warmly here.

Miami's large Cuban-American population has taken umbrage at Mandela's support for Cuban President Fidel Castro, voiced last week in an ABC News interview. Mayor Xavier Suarez and four other Cuban-American mayors in south Florida have denounced Mandela for not condemning human-rights violations in Cuba.

Miami city commissioners have tried to distance themselves from a resolution honoring Mandela, whose sole appearance there is to be a speech to the convention of the American Federation of State, County and Municipal Employees. Cuban Americans planned to picket outside the Miami Beach Convention Center, where Mandela is to speak at 9 a.m. Immediately afterward, he is to depart for Detroit.

Hours before Mandela's 4 p.m. arrival at the King Center where King is buried, crowds of mostly black spectators gathered four and five deep along Auburn Avenue. They stretched in both directions from the center -- toward the two-story brown home a few blocks away where King was born and toward the Ebenezer Baptist Church, where King's father preached.

There were grumbles when the arrival was delayed, and a few complained when the Big Bethel A.M.E. Church filled so fast that some ticket holders could not enter.

Curtis Massey, 37, said he grew up in Flint, Mich., and was in elementary school when most of the civil rights sit-ins and demonstrations took place in the South. "I missed seeing Martin, I missed seeing Malcolm X," he said. "I have to see Mandela."

Young, always campaigning, worked the crowd on the street, then stopped to ponder what Mandela's U.S. visit meant to people standing along the curb.

"I didn't know what you could get out of the March on Washington. I didn't want to go to Washington," he said. "But that defined the dream that changed the southern part of the United States. . . . I don't see yet what Nelson Mandela's visit means to us. But I've learned that these kinds of symbolic acts can be very powerful."