On another morning that dawned clear and beautiful over Lower Manhattan, the families of those murdered in the terrorist attacks of September 11, 2001, gathered at ground zero yesterday.

Four years has passed since that catastrophic day, but to the friends and relatives who congregated yesterday alongside the West Side Highway, overlooking the vast pit where the twin towers once stood, the memories still sting.

“When you come here, and stand here, and know that two 110-story buildings were reduced to dust, it all comes back,” a woman from Longmont, Colo., Hilary Clarke, 60, said.

Ms. Clarke’s son, Gary Box, was a firefighter with Squad 1 in Park Slope, Brooklyn. Box, who was 37 when he died, was last seen on the morning of September 11 entering the North Tower of the World Trade Center.

Her son, Ms. Clarke recounted, was a marathon runner. As tears welled in her eyes, she choked back a sob and said: “I can just see him running up those stairs.”

Yesterday’s anniversary ceremony, Ms. Clarke said, was the first she had attended. She said she had come to hear her daughter, Christine Box, 41, read some of the names of the dead – including Gary’s.

Ms. Box’s tribute to her brother was part of this year’s distinctive stamp on a now-familiar tradition. Since 2002, the centerpiece of the city’s memorial ceremonies has been the enumeration of all 2,749 victims, and this year that task fell to their siblings.

One after another came the tearful tributes to a “beautiful” or “precious” sister, a “loving” or “missed” brother. One man cheered “Go Mets!” in apparent recognition of his brother’s baseball loyalties. At the other end of the emotional spectrum, another man said, to his “baby sister”: “The hole in my heart is deeper than the one you see here.” He gestured to the expansive crater behind him.

Also, as in past years, yesterday’s stirring ceremony was bracketed by four moments of silence – at 8:46,9:03,9:59, and 10:29 a.m. – marking when hijackers slammed passenger jets into the North and South towers, and then when the decapitated structures fell.

The four pauses commenced with the ringing of a silver fire station bell, echoed in the distance by a somber tolling from church steeples across Lower Manhattan. At each juncture, victims’ families were addressed by Mayor Bloomberg, Secretary of State Rice, Governor Pataki, and Mayor Giuliani.

President Bush and Vice President Cheney spent the morning in Washington, D.C., where, according to the Associated Press, they and their wives honored the anniversary with a moment of silence at 8:46 on the South Lawn of the White House.

Though much remained the same from previous commemorations of America’s darkest day in Washington and in New York, yesterday’s salute to the victims came amid a revived sense of national threat and grief.

July’s lethal bombings of the London transit system served as a grim reminder that the struggle against the worldwide scourge of radical Islamic terrorism continues. Closer to home, the pain of losing, suddenly and inexplicably, thousands of American lives was renewed as gruesome reports continued to emerge from the Gulf Coast in the aftermath of Hurricane Katrina.

These realities were acknowledged by Mr. Bloomberg in his prepared remarks yesterday morning.

“Today, as we recite the names of those we lost,” the mayor said, “our hearts turn as well toward London, our sister city, remembering those she has just lost as well.

“And to Americans suffering in the aftermath of Hurricane Katrina, our deepest sympathies go out to you this day,” he added.

The mayor, the governor, and Ms. Rice kept their remarks brief, and primarily quoted verse. Joining them at the ceremony was an assemblage of local and national politicians, including the governor of New Jersey, Richard Codey, and New York’s senators, Charles Schumer and Hillary Clinton.

Of the elected officials past and present at the event, Mr. Giuliani was the most enthusiastically received. During his speech, the former mayor asked of the family members – many of whom carried the images and memories of their loved ones on T-shirts, laminated placards, and framed photographs – “How did New Yorkers respond to September 11 with such strength and compassion?”

“The reason is that we’re all Americans,” he responded. “People who have the blessings of freedom have more strength than they often realize.” Mr. Giuliani was the only politician to draw applause at the end of his remarks.

Applause punctuated the ceremony at several other points, typically as family members used their time at the podium for advocacy.

A favorite cause at this year’s ceremony seemed to be the proposed memorial for ground zero. Families of the victims have protested the International Freedom Center, a museum that plans to acknowledge at the World Trade Center site a wide range of injustices, from lynchings in the Jim Crow South to Nazi genocide in Europe to the gulags of the Soviet Union. Critics of the Freedom Center have denounced it as excessively wide-ranging and even anti-American, advocating instead a specific memorial at ground zero to honor those who died there.

“It’s too broad,” a family member from Wharton, N.J., Wayne Schiele,55,said.”If you want to do something like that, maybe put it at the United Nations.” Mr. Schiele’s sister-in-law, Jennifer Tino, 29, was a vice presi0dent for marketing at the insurance firm Marsh & McLennan and died in the North Tower.

Frustration over the proposed presence at the memorial of a cultural institution seeped into the proceedings yesterday, as one after another the siblings urged that their brothers and sisters be honored with a “fitting” memorial. One urged families to help “keep this ground sacred.”

“We pray politics will not prevent us from putting a fitting memorial down here for you,” another said. One man encouraged his brother: “Don’t worry, Jimmy, we’re going to take back the memorial.”

In the meantime, however, no permanent memorial exists, and families paid their respects yesterday at makeshift markers. As the impossibly long roster of names neared completion, families descended into the pit bounded by the slurry walls that survived the carnage and destruction of the attack.

As the mournful strains of “Taps” carried across the chasm, bringing the ceremony to a close, an attorney who lives and works in Lower Manhattan, Gina Bokios, 34, said she found the event very moving.

On the morning of September 11, Ms. Bokios recalled, she was aboard an American Airlines flight from New York to Chicago. “We must have been one of the last flights over the World Trade Center,” she said, remembering that she had passed the twin towers around 7:30 that morning. Three hours later they were gone.

The sense of disbelief that millions felt upon hearing of the towers’ destruction has not diminished for Ms. Bokios.

“I can’t believe it was four years ago,” she said. “It seems like yesterday.”

One city firefighter spent part of the day in jail. Edward Dailey, 27, of Firehouse 50/Ladder 133 in Queens, was arrested after allegedly instigating a fight with a newsstand employee while purchasing chewing gum. While wearing his dress uniform pants and fire department shirt at 5:10 p.m. yesterday, Mr. Dailey got into a verbal dispute with a newsstand employee in front of 123 Mc-Dougal St., police said. Mr. Dailey – the 2004 firefighter class valedictorian – said to the employee, “You look like Al Qaeda,” police said. The firefighter then reportedly ripped off a piece of Plexiglass from the stand and hurled it at the victim, injuring the employee’s hand. The victim was taken to St. Vincent’s Hospital. Police charged Mr. Dailey with criminal mischief and assault.