`Heroes and the Test of Time' looks at Custer and Eakins

``National Geographic'' had better move fast if it intends to maintain its position as the No. 1 nonfiction show on PBS. ``Smithsonian World'' gains a few giant steps with each of its outings. Heroes and the Test of Time (PBS, Wed. April 24, 8-9 p.m., check local listings) is the spring season premi`ere of ``Smithsonian World,'' and it manages to combine two seemingly incongruous episodes into one solid, smashing nonfiction show. Featured is one of America's greatest painters, Thomas Eakins, and one of America's most flamboyant military leaders, George Armstrong Custer.

``Smithsonian World,'' under the aegis of executive producer Martin Carr and writer Michael Winship, with the instructive but never loquacious David McCullough as guide, manages to fuse the two fascinating figures into an hour of smoothly informative entertainment.

The special charm of ``SW'' is its ability to link facts, concepts, people, so that viewers learn about the time, place, and personality without being self-consciously aware of the process of either education or entertainment. With ``SW'' it just happens.

Everybody has heard of Eakins and Custer. What this program does is place them in the perspective of time -- the late 19th century. And it tries to separate fact from fiction, legend from reality with beautiful illustrations and a limited dramatization, completely valid in this format.

Most viewers will learn more about Eakins and Custer than any single textbook could tell them -- and they will be able to enjoy every moment in this journey into the hero mystique. Were they heroes, martyrs, fakers, madmen? McCullough presents all sides and then lets us create our own reality.

``Smithsonian World,'' underwritten by the James S. McDonnell Foundation, co-produced by WETA/Washington and the Smithsonian Institution, is a prime example of the ``television of awakening'' which is being pioneered on PBS. It provides the shock of intellectucal revelation with the warmth of cozy entertainment.

The Smithsonian -- one of America's most important educational institutions and a storehouse of the past, present, and future -- has found a superb electronic way to reach out and allow its treasures to be touched by every American.