Blacks who think they have few clues to their family's past may actually have more than many whites, according to a genealogist lecturing this month at Martin Luther King Jr. Library.

James D. Walker, a retired archivist and author of a textbook on black genealogy, said the birth, death, sale and transfer of slaves generated thousands of records through which it is possible to trace families otherwise anonymous in the sometimes fragmentary census records of past centuries.

"Until about 1960 it was difficult to get access to many genealogical sources," Walker said. "We simply didn't know where they were."

But the increasing microfilming and indexing of vital statistics, court records and agency reports has put one's ancestral history within relatively convenient reach of anyone in the Washington area, he said. All that's needed to find it, in most cases, is time.

"Most people have no conception of the wealth of material available to them," he said. The Freedman's Bureau of the Treasury Department, for example, which fed, clothed and found jobs for blacks and indigents in the South between 1861 and 1869, is a superb source, Walker said.

Each of some 300,000 depositors in the banks set up by the bureau around the country was required to list his name, age, sex, occupation and place of residence; the names of his spouse, children and brothers and sisters and their places of residence; the name of his former owner and the whereabouts of the plantation, and a physical description of himself.

"If you find an ancestor who was a depositor, you've hit a gold mine of information," he said. Bureau records are open to the public free at the National Archives.

In addition, he said, the Mormon Church has copied virtually every birth, death and marriage record in the country, plus local county documents and even some records from other countries. The microfilm is available through the church's branch libraries in Silver Spring, Oakton and Annandale, as well as in the church's main depositories in Salt Lake City.

Walker, currently giving library workshops during Black History Month, said the most common misconception among his students was "the belief they are descended from nobody noteworthy.

"But when they master these few techniques and begin searching, they usually find their people were landowners . . . church members . . . artisans--people active in the communities" of rural 19th-century America.

Like author Alex Haley, whose "Roots" turned the nation's already growing interest in genealogy into a boom, Walker's students find a curious comfort in their links to the past.

James Watts, a 42-year-old computer specialist from Upper Marlboro, sought Walker's counsel after perusing Freedman's Bureau records since October to trace six generations of his family back to an ancestor who, he had discovered, was a machinist in 1871 in Lafayette County, Arkansas

"I always knew my family was from Arkansas," he said, "but now I find they got there from Virginia, North Carolina and Maryland. And now I live in Maryland. Sort of back where they started."