June 29, 1984

Every other Thursday at City Hall, a Cornell-trained economist from upstate who looks younger than his 28 years sits in a tall leather chair that is capped by a carved eagle. At that moment, in that place, the economist, John J. Gilbert 3d, is the Mayor of the City of New York. This is Board of Estimate day, an almost seamless stretch of public hearings, votes and horse-trading that can spill over into the next morning. It features a cast of characters very different from the nameplates around the U-shaped dais. The eight elected officials who make up the board are rarely seen. Instead, they send deputies, assistants and other aides.

An article in Business Day June 4 about utility name changes misidentified the main subsidiary of the Florida Progress Corporation. It is the Florida Power Corporation.

An obituary last Saturday, of a former writer for Better Homes and Gardens and The Ladies' Home Journal, misidentified her. She was Gladys Denny Shultz.

CBS Inc., which two years ago raced to be one of the first communications companies authorized to build a satellite-to-home television system, yesterday abandoned the project, citing ''some open questions and the risks involved.'' In a terse statement, the company said it would not meet a Federal Communications Commission deadline to begin construction on the project by next month, meaning CBS will be forced to surrender its building permit. Analysts said the move, which came as a surprise, aroused doubts about the future of the direct broadcast satellite industry, in which television programs would be beamed straight from orbital satellites to small antennas on rooftops. More immediately, it appeared to jeopardize the future of the Satellite Television Corporation, a subsidiary of the Communications Satellite Corporation. Comsat had been negotiating with CBS since December on a joint venture in the new field. Both Comsat and CBS officials, however, had made it clear recently that they would not go ahead unless they found a third partner to share the costs.

Leftist guerrillas overran El Salvador's largest hydroelectric dam today in their most important military operation in the last six months. Government forces were reported to have retaken the dam later in the day. During an eight-hour battle with Government forces that started at 2 A.M., the rebels destroyed the 135- megawatt Cerron Grande dam's electrical generating substation but did not destroy the plant's central computerized control room. The dam is 25 miles northeast of San Salvador in the heart of a heavily contested guerrilla zone and has long been considered a prime target for rebel attack. The assault today was the biggest rebel operation since the guerrillas destroyed the army's base at nearby El Paraiso last December and the Cuscatlan bridge, one of the country's largest, at the beginning of the year.