His accent was Red River Valley. Hers was Moscow. They were face to face across a dais in the Rayburn House Office Building, a rare setting for a meeting of superpower minds.

Rep. Ralph M. Hall (D-Tex.), courtly chairman of the House subcommittee on international scientific cooperation, found his down-home pronunciation of Russian names being corrected, in the manner of a bemused schoolmarm, by Prof. Valeria Alexeevna Troitskaya, deputy director of the Soviet Geophysical Committee and a leading expert on electromagnetic waves and their use in studies of the upper atmosphere and space.

She was one of three top Soviet scientists who flew here from Moscow this week to testify at the subcommittee's hearing on a burgeoning international effort to deal with changes in the global life-support system of air, water, forests and so on that are occurring as a result of human activity.

Testimony on Capitol Hill by any Soviet representative is rare enough and has been given in the past by diplomats or scientists already in the United States for another purpose. But this time, to the panel's surprise, the Soviets dispatched a delegation from Moscow.

Europeans and the Japanese declined invitations.

Troitskaya was accompanied by snow-and-ice expert Vladimir Mikhailovich Kotlyakov, director of the Institute of Geography of the U.S.S.R. Academy of Sciences, and zoologist Vladimir Sokolov, director of the academy's Institute of Evolutionary Morphology and Ecology of Animals. They used their interpreter only rarely, for a word or phrase.

The Soviets presented the members with a book, in Russian, on the topic at hand, and with formal statements on the Soviet Union's passionate commitment to cleaning up industrial pollution and generally keeping the planet livable. Merely avoiding nuclear war, Sokolov said, is "not enough."

"You should meet more often with scientists," Troitskaya, whose hair is the color of Ukrainian wheat, told Hall. "It will help you in your political life."

"I'm interested in that," he said smiling.

When Rep. Harris W. Fawell (R-Ill.) asked Troitskaya what is the greatest threat to the environment, she responded with a smile, "You put not the right question," and suggested a more productive approach.

"Let me try another one," Fawell said, laughing along with audience.

The Soviet scientists spoke repeatedly of the "interconnectedness" of nations and their problems. And Sokolov stated that "50 percent of pollutants enter our country with precipitation from neighboring territories." However, none of the three mentioned the nuclear disaster at Chernobyl. Fawell asked Troitskaya about it. "A big lesson," she responded quickly.

The Soviets have become very sophisticated in pursuing their agenda in dealings with Americans, according to a Sovietologist in attendance. "Americans still tend to be 'gee-whiz.' We've got to get sophisticated, too."