"Once again, as this city sweeps up the glass and puts itself back together again . . ."

Mayor Dianne Feinstein was using her calming voice again. Steady. Deliberate. She spoke that way last November, when Mayor George Moscone and Supervisor Harvey Milk were shot to death. Down below her office, down in the park where the trees and police cars burned Monday night, people had gathered to look at what was left of the big shattered City Hall doors.

The outburst of arson, vandalism, looting and battles between police and an estimated of 5,000 protesters - which was being described by witnesses as the worst in the Bay area since the People's park incident of 1969 - followed the conviction of former city supervisor Dan White on reduced charges in the deaths of Milk, an avowed homesexual, and Moscone.

San Francisco police had no official comment today on the disturbances, which began about 7 p.m. Pacific time about an hour after jury members announced that White had been convicted on voluntary manslaughter, which carries a maximum sentence of less than eight years.

The prosecution had asked for the death penalty. The verdict was perceived by most gays - as well as many others, including Mayor Feinstein - as a disturbing victory both for White and for the anti-homosexual sentiments his trial seemed to have stirred within San Francisco.

Tonight, a gathering to commemorate the birthday of Milk, who represented a district including the Castro Street neighborhood, which is predominantly gay, was peaceful.

From the first notes of "Happy Birthday to Harvey," sung by a crowd of 7,000, it seemed Castro Street had something it lacked completely 24 hours earlier - harmony. The event celebrated what would have been Milk's 49th birthday.

Three hundred monitors trained today in nonviolent techniques of crowd control patrolled the streets. Popular singers Hoily Near and Meg Christian led the throng, predominantly homosexuals, through low-key political ballads and handclapping rock songs.

Partygoers lined the rooftops, leaned from windows and huddled on a movie marquee. The fog-gray sky and chill breeze helped to cool tempers.

Monday night, several hundred demonstrators, according to witnesses, gathered on Castro Street for what was publicized as a march to City Hall for a candlelight protest vigil. But the march grew in both size and anger as it approached City Hall, and by 8:30 p.m. the crowd massed before the big doomed building was shouting, "We want Dan White!", "We want justice" and "White was a pig".

Several march leaders tried to address the crowd through bull horns, but as one demonstrator said shortly afterward, "the platitudes just weren't going to do it. We had a right to be angry." Police in riot helmets gathered inside City Hall, where a regular scheduled supervisors' meeting was in progress upstairs, and sometime around 8:30 p.m., as the demonstrators massed on the City Hall steps, glass shattered in one of the wide front doors.

Cheers followed the crashing of the door panels. When supervisor Carol Ruth Silver walked out onto the front steps a few moments later to attempt to calm the crowd, she was hit in the mouth with a rock and was taken to a nearby hospital, where she received 20 stitches in her upper lip.

By 10:45 p.m., the block-long park in front of City Hall looked as though it were in flames. Fires had been lit in trash containers, piles of signs, and shrubs, and on the streets surrounding the City Hall building, lone police cars sat in flames their sirens wailing.

Several reporters said they saw police throw at least three teargas canisters into the crowd - police denied having used any - and the air for blocks was thick with acrid black smoke.

Witnesses said the violence increased about 11 p.m., when police moved in a solid line across the plaza in front of City Hall, pushing the crowd - by now made up of demonstrators and passersby who had joined in - before them.

As they fled, some people picked up concrete chunks from a construction project near the old Beaux Arts-style library and pelted the formation of police.

The police raced forward with clubs raised, witnesses said. Among those injured by police were several members of the working press including a reporter and an assistant city editor for the San Francisco Chronicle, and Washington Post special correspondent Bill Wallace, who required 10 stitches in his scalp after being thrown to the pavement and billyclubbed. "Each one who came by took a whack at me with his stick," he said.

Another journalist badly beated was Paul Krassner, former editor of Hustler magazine who has been covering the White trial for a Playboy article. Krassner suffered a fractured rib and punctured lung. He was hospitalized and later released.

About 120 civilians were treated at local hospitals, according to a check of emergency rooms. At least 59 police officers were also treated for injuries.

"I'm sorry you got hit," a young man said to a police officer, who stood near City Hall with nightstick in hand and a slow trickle of blood down one side of his face. "It ain't right," the young man said. "But I can't agree with the verdict."

The police officer looked at him and shifted his club slightly. "Yeah, well," he said. "This is no way to show it."

Toward midnight the police began to fan away from the City Hall area. A reporter heard officers cry "Hey, fag!" and shout to a woman inside a parked car, "They're taking over the F------ city. It's our turn now!"

By early morning several dozen policemen had reached the Castro Street area. According to many witnesses, including reporters, more than a dozen of the officers, in full riot gear, swept into a gay bar with clubs swinging.

Spokesman for the mayor's office said police officials were looking into the bar incident, but would not comment on it today.

The violence so jarred foreman George Mintzer, he told the San Francisco Examiner, that he felt compelled to break the silence he had maintained about the jury's deliberations. Mintzer told the Examiner that the Jurors never seriously debated convicting White of first-degree murder - "No one could come up with any evidence that indicated premeditation," he said - and that they had reached their verdict of voluntary manslaughter because they felt they could not prove beyond a reasonable doubt that malice was involved in the shooting.

In White's neighborhood, many miles from the sound and smell of the City Hall violence, a working-class bartender who had known White said of the verdict, "I was very happy. I think it was great." The bartender said he could understand the bitter reaction of gays to the verdict, but thought "they went overboard," and the police "showed remarkable restraint."

The bartender added, "They could probably put up a Statue of Liberty here with a sign on it, saying, 'Send us your kooks and wierdos.' But the gay people don't bother me and I could care less."

Added a bar patron, ruefully, "It makes San Francisco look like the cuckoo capital of the world." CAPTION: Picture 1, San Francisco police and demonstrators clash at City Hall late Monday after verdict in White trial set off outburst of arson and looting. AP; Picture 2, At least five San Francisco police cars go up in flames near City Hall after being torched by protesters angered by verdict in Dan White murder trial. AP; Picture 3, A police car burns against lighted backdrop of San Francisco's City Hall. AP