THE day before, demonstrators had marched from Post Office Square to the Berkeley St. Police station to protest the trial of Bobby Seale. They had rallied in the street in front of the station, and the cops with movie cameras did not even have to leave their offices to add films of subversives to their files. Dong Miranda, an official of the New England Panthers, and Rafael Rodriquez from En la Lambrecha, a Boston Puerto Rican group, had spoken from the roof of the sound truck-the same sound truck in fact, which was leading the march down Beacon St.

After the rally at the station Tuesday, the marchers had moved down Berkeley St. to Commonwealth Ave. Blocking the northbound lane, they had marched to Kenmore Square, singing "We love Bobby Seale, we love Bobby Seale, deep down in our hearts," and shouting "Join us" to the onlookers who lined windows and rooftops along the way.

But as the marchers in the front shouted, "Join Us," those in the rear had been quietly disappearing, filtering into MTA stations and side streets, perhaps intimidated by the five police wagons which were following quietly behind. When the march reached Kenmore Square, there had been about 309 people left, surrounded now by police cars which had rushed north in southbound lanes and lurched over the grassy medians to be in position to move in.

At Kenmore Square, a few rocks had crashed through the windows of the National Cash Register office. Some people laughed, and a lot of people left. The march had petered out shortly afterward.

The situation was objectively the same on Wednesday, as this Bobby Seale march moved down Beacon St. Only nobody was laughing. And nobody was leaving.

A FIRE ENGINE was blocking half the street at 411 Beacon St., and derisive howls came from the crowd as it neared the obstruction. Some old lady had set fire to a hamburger in a frying pan, no doubt. More fire engines were coming south along Beacon St., accompanied by police cars. As a patrol car inched through the crowd toward the fire, one marcher produced a bowling ball from beneath his coat and heaved it through a side window in the front seat. The cop jumped out, but his riot helmet, improperly fastened, flew off his head and rolled into the gutter. By the time he had retrieved it, the crowd had flowed through the trucks and the vandal was out of sight.

The sound truck was broadcasting constant warnings: "Don't break windows or we're not going to make it to Harvard Square. The Red Army's going to make it to Harvard Square. The Black Army's going to make it all the way to the Pentagon." Some of the marchers were carrying laundry bags of rocks. Few threw them on Beacon St.

Many of the marchers were high-school students and street people from communities around Boston like Fall River, Lowell, Dedham. NAC members had been organizing them during the winter. These were kids who had no trouble regarding cops as the enemy, who had no reticence about fighting and breaking windows. Abbie Hoffman had asked at the big rally at the Common, "How many here are going to rock the cradle and how many are going to cradle that rock?" These kids were ready.

As the march turned onto the Harvard Bridge, it first became apparent that this march was going on, that something was going to happen. Very few of the marchers-perhaps 400 at most-peeled off when the crowded flowed onto the bridge, blocking traffic in the eastbound lane. The Lawyers' Guild representative-exhibiting an icy cool in the midst of the confusion-conferred with the sound truck and then moved ahead of the march to talk to police representatives. He again showed them the permit, which cleared the marchers all the way to Harvard Square. The police cars and cycles began turning around and heading back toward Boston to the applause of marchers-"Little piggy, I think you better go now. Oink, oink, bang bang, dead pig."

A stalled car blocked the eastbound lane, and cars began turning back towards Cambridge and inching through the crowd. Marchers laughed and hit the fenders with their hands, evoking nervous smiles from the drivers. The crowd at the head of the march sat down, immobilizing the cars completely. One marcher shouted, "Let's stay here on the bridge all night."

After a minute, a NAC marshal came up and shouted angrily. "This is the front, huh? What's happen-

ing?" Shamed, the marchers got to their feet and moved forward again.

THE MARCH entered Cambridge in the cerie half-light of late dusk. The streetlights gave some light, but the glow in the sky behind the buildings lent the situation an unreal air. Marchers could not see the faces of those marching next to them. As the crowd progressed down Mass. Ave, toward Central Sq., files of cops, wearing riot helmets and carrying tear-gas guns, came into view at the side of the street. Advance scouts rushed ahead to survey police formations, then returned with exact reports on their number and armament: "There are 96 cops up there, with dogs." The cops stood silently at the sides, not in front of Buckingham Palace. Uncertain of the marchers' intentions and destination, they watched and waited. The Cambridge police wore soft blue hats and badges. The Tactical Cops carried riot batons, and wore black leather jackets with two white holes where their badges were usually pinned.

Hundreds of police and spectators lined Tech Square. Radicals considered M. I. T. a target. police knew. Students in windows gave the marchers the clenched fist; but the marchers shouted back at them angrily. Some taunted the cops and others threw rocks through windows of Tech buildings. The sound truck urges the students to ignore M. I. T. and go to Harvard Square: "We're going to Harvard Square and groove all night." The police made no move to stop the march, and the crowd streamed through the square without pausing.

The big flashing thermometer/clock was showing 6:54 as the marchers entered Central Square. The tension had been building as the light ebbed-the marchers knew that they were going to do something, and they wanted to start. March officials had decided earlier that any action in Central Square would be bad politics-an attack on the working people of Cambridge, who owned most of the businesses there. But the troops of the Red Army were restive. The demonstration had originally been announced as ending at Tech Square, and some people felt that action was overdue. Rocks began flying through the windows of the Cambridgeport Bank.

Marshais scurried back from the sound truck, which again urged the marchers to cool it. NAC members began rapping with the kids throwing rocks, explaining that Central Square was not a good target. A few kept throwing rocks, and the crowd began chanting "Cool it-Cool it-Cool it" as the body of the march passed through the square.

After Central Square, the tension in the crowd rose enormously. The target was almost in sight, and many people were just beginning to realize that something big was about to happen-that few people had left the march since it crossed the bridge, that kids were really ready with bags of rocks, that 1500 people were enough to do more than crash one window and run. Marchers looked around at each other with a new awareness. The kids who had tried to drown out Doug Miranda on the Common by yelling "Peace now"-the good vibes kids, the clean-cut, happy SMC kids, the apolitical hippy-freaks who could groove on green grass and sunshine and 60,000 people waving peace signs and singing "All we are saving is give peace a chance"-they had been left far behind.

So for the moment, were the police. They had apparently thought that the permit to march to Harvard Square was a ruse and prepared for assaults on M. I. T. and the Cambridge Draft Board. When the march entered. the policemen in the Square were very few-and very scared. Marchers seemed almost stunned by the fact that they were alone in Harvard Square. The sound truck, having shepherded the marchers safely to the target, turned and scooted down Arrow St.

The marchers milled around, confused, for about a minute. Then a rock smashed through the expensive, intricately stained front window of Krackerjacks. Then another. And another.