MONTGOMERY, Ala., March 19--Four night demonstrations have been held here this week, keeping state troopers and city police on irregular night shifts.

At 7 p.m. CST tonight, 34 pickots, most of them Negro teenagers, arrived in the Capital Building.

State troopers, wearing white and blue slickers, conservation officers in their green raincoats, and city police in yellow slickers lined the streets. Freedom songs, the roar of motorcycle engines, and the crackle of police radios all blended with the sound of the rain. The immense white Capitol Building, lighted by floodlights and glistening in the rain, loomed above the troopers and the pickets.

On Monday night, 200 civil rights advocates sat down on a section of High St. when police refused to allow them to march to the Capitol Building.

Eheriff's horsemen were used that night to clear Negro onlookers from the scene. Some Negroes were beaten by the riders and trampled by the horses, while nearby radion carried the President's voting rights spoech.

About 35 clergymen began a vigil in front of the Capitol at 10 p.m. Tuesday to protest the beatings of that day. They asked if they could give a prayer on the Capitol steps, but a tight ring of state troopers prevented any movement toward the steps.

Finally at 2:30 a.m. Wednesday, the ministers, rabbis, and priests were allowed to kneel on the first step and recite the Lord's Prayer. But the troopers insisted on forming a line, shoulder to shoulder on the second step, to prevent any assault on the building.

Last night 49 pickets paraded around the City Hall, from 6 p.m. to midnight. Police arrested them when they began to rest by sitting on the sidewalk.