Under the tranquilizing air of North American civility and orderly procedure, a political time bomb is kicking away in the heart of Canada that threatens to destroy the 114-year-old Canadian federation.

The timer is set for May 20, when the voters of the predominantly French-speaking Quebec will be asked in a referendum whether they favor independence for their province. The outcome, as author and journalist Peter C. Newman put it, will decide "Canada's existence as much as Quebec's future."

Yet, this country's English-speaking majority seems frozen in immobility and the belief that the current predicament is somehow less lethal than revolutionary turmoil in Central America or other distant places.

Quebec is the largest of Canada's 10 provinces and nearly 80 percent of its 6.2 million people are of French anestrty. An independent Quebec would split Canada into two parts, the Maritime Province on one side and Ontario and western provinces on the other.

With an independent Quebec, a rump Canada would eventually fall further within U.S. economic orbit, but not without major social and political turmoil that is deceptively minimized by the civilized surface of Canada's crisis.

Serious political observers have suggested that no matter which side prevails in the referendum, the results carry the potential for violence in Quebec.

With the latest polls showing the separatist forces slightly ahead of those who favor Quebec's continued allegiance to the federation, Prime Minister Pierre Trudeau repeatedly has raised the prospect of collapse. He urges Quebec to vote in favor of national unity, "destroying doubts about our ability to continue to act as one strong country."

But Trudeau's considerable moral and political energy has failed to rekindle a discernible interest and passion for national unity either in English-speaking Canada or here in Quebec.

This is due in part to the ambiguous question on the May 20 referendum in which Quebec residents will be asked to give the separatist government of provincial Premier Rene Levesque the mandate to negotiate a sovereign Quebec that would maintain economic association with the rest of Canada.

English-speaking Canada has made it plain that is has no interest in such an arrangement, which one politician described as "divorce with bed privileges." Trudeau, himself from Quebec, was even more unequivocal. The federal government, he said, would not negotiate with "a government bent on destroying the nation."

Ignoring Trudeau's warnings, much of Anglophone Canada sees the referendum as the opening gambit in a long game and an opportunity to take the next card in the deal without cost. Giving Levesque the mandate to negotiate does not suggest a final decision. There is, in this view, quite some distance between the ambiguous "sovereignty-association" premise and actual separation.

Moreover, English-speaking politicians, especially in wealthy western Canada, are so preoccupied with parochial loyalties that they view a strong federal government as a threat to their fiefdoms.

While Canada has a deficit of $13 billion, the three western provinces have a combined surplus exceeding that amount. They do not want to see Ottawa touch it, however.

As a result, the leaders of the newly affluent West have viewed Quebec as a strategib beachhead from which to mount an offensive against the federal government's attempts to gain control over their resources and wealth.

For the French separatists, the May 20 referendum is a landmark event in the inevitawble sweep of history. It is not any opening gambit but the first, and for them the most crucial, move toward independence.

As descendants of early 17th century French settlers who later were subjugated by the British in the 1759 battle at the Plains of Abraham, the French separatists now have cast themselves in the role of a remnant of British colonialism. Traveling through Quebec in 1831, Alexis de Tocqueville noted that the French constituted "the immense majority" of the population but that "it is easy to see that the French are the conquered race."

Until relatively recently, the predominantly rural and Roman Catholic French Canadians lived a separate life from Quebec's English, Protestant minority, who mostly lived in Montreal. The English-speaking elite almost exclusively controlled the banks, big companies and economic life in general.

In a rapid succession of events, the French majority has moved in to wrest political and economic positions in Quebec and to achieve a higher standard of living. In 1961, the average French-speaking worker here was earning 50 percent less than his English-speaking counterpart. By 1976, that gap had been narrowed to 15 percent.

Many of these advances coincided with the activities of Parti Quebecois, the separatist splinter group established by Levesque in 1967 that swept to power in the 1976 provincial elections. The federal government under Trudeau, however, also has passed major legislation designed to redress past grievances and make the French-speakers feel a genuine part of Canada.

Yet, at the heart of the separatist drive is a notion that transcends politics and ideology, entering the misty realm of language and culture. The Quebecers in general regard themselves are being an outpost of a distinct culture surrounded by a numerically greater English world, which, in turn, shares a 4,000-mile border with the largest English-speaking culture in the world.

The question is how to preserve the distinct character of this outpost. For Trudeau and the federalists, the safeguarding of Quebechs heritage, as well as that of more than 1 million French-speaking people in other provinces, can be achieved within a democratic, bilingual Canadian federation.

For Levesque, independence is the only path. "I hope we get there the civilized way," he has said.

The separatists point out with considerable pride that Quebec is larger than France and Spain combined. It is rich in iron, copper, zinc, timber and especially asbestos. Numerous rivers give it huge reserves of hydroelectric power. With its production of aluminum, textiles and shoes, Quebec's gross product stands about $50 billion, far larger than the gross national product of most independent countries.

Yet, as Trudeau pointed out last week, if the refrendum question "simply asked: 'Do you, yes or no, want independence?' Quebecers would say no."

By seeking the mandate to negotiate independence in economic association with the rest of Canada, Levesque has found an ingenious tactical approach, suggesting to Quebec citizens that they can fulfil their aspirations at no cost.

For those who want a better deal for Quebec but want to remain in Canada, Levesque has promised a second referendum that would seem to be adequate insurance against dramatic change. These voters respond to Levesque's appeals to their pride and fear -- pride that they can affirm their national distinctness and fear that if they do not, they are doomed to extinction.

"It is our collective duty to widen our horizons, to push back their limits," Levesque said repeatedly as he campaigned last week. "If we continue to be manipulated excessively from the outside as we are now, we will never attain the potential and goals we have a right to."

The message, which pierces the soul of Francophone Quebec, is that endorsement would correct "the inequality of our two peoples" and that without the brutal shock of a "yes" vote, Anglophone Canada would either ignore Quebec or laugh at it.

For the leader of the federalist cause, Claude Ryan, this message is hard to match. He has to sell a negative case -- that the rejection would spur Canada into correcting inequalities through a new constitution that would accept the two-nation concept of Canada. Both Ryan and Trudeau have accused Levesque of being a demagogue determined to achieve independence and Trudeau has warned that there is a "very, very real" chance that Levesque would unilaterally declare independence if he wins the referendum.

William Johnson, a Toronto Globe and Mail columnist who has written exclusively about Quebec for several years, said this week that "large-scale terrorism and civil disturbances" could result whatever the referendum's outcome.

If the separatists win the rest of Canada refuses to negotiate, "that is a formula for riots," Johnson said.

A federalist victory would also be dangerous because a large proportion of Quebec's population would refuse to recognize its legitimacy and militant separatists would turn against Levesque's gradual approach.

The depth of conflict there and its unsettling prospects worry American diplomats. Nearly $50 billion in U.S. investments and the traditional good relations give the United States a major stake in what happens in Canada.

But Washington apparently has no other choice but to stay above the battle.

Visiting Secretary of State Cyrus Vance disappointed his Canadian hosts last week when he asserted that the Quebec issue was an internal Canadian matter to be settled by Canadian. When asked by journalists, he refused to repeat a statement he made in Ottawa 19 months ago that the United States hoped that Canada "will remain united."

"All of us hope that this great, rich country will remain united," Vance told Canadian government and business leaders in 1978. "The decision is one for which Canadians must find their own solution. All Americans want to continue working and living together with a united Canada as our best and our closest friend."