A pewter sky hangs over Washington Cathedral, appropriate weather for Anglican Washington. Schoolboys in blue blazers gambol on the tarmac, and the sound of carillon bells carries across new-green lawns and the playing fields of the Cathedral close.

Church House, on Mount St. Alban next to the Herb Cottage, is the headquarters of the Episcopal Diocese of Washington, and of the Right Rev. John T. Walker, the second (and currently the only) black Episcopal diocesan bishop in America.

Walker might well have been a bureaucrat instead of a clergyman. In 1944 he worked for the Post Office in Detroit--and quit. "There was a lot of laxity," he says. "Angry men broke the contents of packages marked 'fragile.'"

Bishop Walker does not break things; however, his restraint can be deceptive. When he took over the diocese in 1977 and discovered that the cathedral was $11 million in debt, he scrapped the office of dean of the cathedral and assumed those duties himself. That outraged some people, particularly those who wanted an autonomous cathedral.

"If I had appointed a dean, he would have been independent," the bishop said. "Every time I disagreed with him, I would have gotten into a big hassle. I wanted stronger control."

He has hazel eyes and a soft, accentless voice, a slight man who tucks his pectoral cross into the pocket of his purple shirt. "He's shrewd, polished, and offensive to no one," says a fellow priest, with respect. "He has done an extraordinary job in a lily- white place, getting various groups to think they're making decisions when in fact he makes the decisions."

He was the first black student at Virginia Episcopal Seminary in Alexandria, the first black rector of his parish in Detroit, the first black teacher at St. Paul's School, in Concord, N.H. Asked what it was like being a black man rising through the white establishment of the white establishment's church, he pauses, and says, "Let me tell you some things."

His father, a Baptist, gave up farming in Georgia because of racial ill-will, and went to Detroit. He looked for a steady job throughout the Depression, and eventually got one with the Works Projects Administration. His family lived in a neighborhood composed of blacks, Italians, Syrians, Lebanese and American Indians. "The whole question of race was not a conscious problem" until he became a young man.

His mother was a member of the African Methodist Episcopal Church, to which her sons belonged. She was determined they would be educated. After high school, Walker worked in the War Department in Detroit, but was RIFed. At Wayne University, he "fell in with what would today be called 'social activists.' They wanted to change things." He joined the NAACP, and helped integrate--or close--restaurants near the university that wouldn't serve blacks.

His new friends were Jews, Episcopalians and agnostics, and he joined the Episcopal Church. The bishop encouraged him to apply to the Protestant Episcopal Theological Seminary in Virginia after graduation, which Walker did, "although I was quite worried." The seminary was in the South his father had fled.

"It never occurred to me that I would be a bishop. I wanted to be the rector of a parish, and a teacher."

Seminary proved to be no problem. Back in Detroit, Walker got an offer to teach history in the Eton of American Episcopalianism, St. Paul's. "I really wasn't being asked to do something for racial reasons. He said, 'You're not going to lose your temper.' All those years (in Virginia) had prepared the way for me, if I wanted to take advantage of them, but I had no intentions."

During a year's sabbatical in East Africa, Walker received a letter from the redoubtable Very Rev. Francis B. Sayre Jr., then dean of the Cathedral, asking him to be a canon here. Walker's wife, a Costa Rican, did not care for New Hampshire winters, and Walker accepted Sayre's offer.

"Being in a place like this obviously opens doors. But I had no other aspirations. When I was elected suffragan bishop I didn't really want to run, but a black woman said, 'You can't refuse. There's only one black bishop in the country. You have contacts, and that makes it possible for you to win.'" He won. The discovery of the debt caused him "great depression--I realized I would have to spend the first few years raising money." If people initially outraged are still so, they don't let on, for the debt has been covered and construction continues.

"Politics," Walker says, in a homily that does not always apply to that other hill across Washington, "is the arranging and accommodating of life in this world. I don't think of politicians as evil people. They are elected, and have to carry out responsibilities. What's important is how power is used."

Which brings us back to the original question. When he is out of the shadow of the cathedral, preaching to Sunday confirmation classes in other churches, Walker looks out over a different sort of congregation.

"The Episcopal Church is not an establishment church. It's not just people at the top of the ladder. It's one of the most diverse institutions in America, racially and ethnically, with many parishes of working people."

His life is full of meetings, sermons, events, advising, fund-raising. "He tells the clergy not to work too hard," says one of them, "and then sets a poor example."

He supports the nuclear freeze, and has designated a task force within the diocese to make an issue of man's potential self-destruction. However, he's only afraid, he says, of "making a big, wrong decision that culminates in pain for others, and for me."

There is one final step up --to presiding bishop of the Episcopal Church of America, a post that falls open in 1985. That's based at what's known to insiders as "815," the address on Second Avenue in New York where reside both the power and the glory of the Episcopal Church of America.

"I'm not even optimistic enough to think of that happening," says the bishop, with obvious sincerity. "I would be happy here until I died." And then, with equal sincerity, "Presiding bishop is not really a job one should turn down."