THE STARTLING fact about South Africa is not that an occasional riot or police action brings white repression and black unrest into the news but that there is, relatively speaking, so little evident protest. The immense blanket-like white police apparatus, Soviet in quality, makes protest prohibitively costly for most people most of the time. Moreover, among the politically powerless black majority there is a wealth of patience and stoicism that is awesome, verging on incomprehensible, especially in light of the massive provocation and offense to which blacks are routinely subject.

It is significant, then, when racial violence takes place on a scale large enough to draw notice. It happens every few years, and it suggests the depth of the feelings -- fear among whites, rage among blacks -- that form the real social base. Such a flaring has just taken place in some of the segregated slums ("townships") where blacks are forced to live around Johannesburg. The proximate causes were the usual last straws: increases in rents and things of that nature. Young people were active in the streets. Most violence was directed against the targets closest at hand -- the black facilities (beer halls, municipal buildings) and officials regarded as surrogates for the whites' apartheid system. Children as young as 6 were among the more than 20 blacks killed in what authorities called "police countermeasures."

As it happened, the riots took place the day white South Africa inaugurated the new constitution by which it has meted out a sliver of political participation -- but not real power -- to its Asian and Colored minorities. Whites designed this "new dispensation" precisely to continue denying even a weak political voice to the black majority. Just as the low Asian and Colored participation has constituted one judgment on the new political scheme, so the riots constitute another.

One of the townships in which conflict broke out over the weekend was Sharpeville. You will recall Sharpeville. In 1960 police there machine-gunned a crowd of demonstrators, killing 69. The massacre led to the formation of the black revolutionary organization, the African National Congress, the white minority's nemesis to this day. Its leadership was drawn from blacks such as Nelson Mandela -- still recognized as a ranking figure although he has been a political prisoner for 22 years -- who had tried and failed to achieve a legal political role.

Even as the embers smoldered in Sharpeville, the third bomb in two weeks exploded in a government building in Johannesburg. Who believes that this bombing, or the latest riots, will be the last?