A museum of the air is one thing, a mausoleum of the air another. "Smithsonian World" returns tonight for what will apparently be another drowsy-fusty season of well-meant but tedious public TV specials. "Heroes and the Test of Time" airs at 8 on Channel 26, which produced it, and other public TV stations.

No treat for those who like their television -- even their public television -- with a bit of zip to it, "Smithsonian World" hardly does for the Smithsonian Institution what the National Geographic specials do for the National Geographic Society. The "World" programs don't communicate the vitality of the sponsoring organization.

The two "heroes" chosen for examination on tonight's program are 19th-century American painter Thomas Eakins and Gen. George Armstrong Custer, the legendary functionary who got his clock cleaned at Little Big Horn. The Eakins sequence is particularly dry and tepid. We see a lot of men-rowing footage that dissolves into Eakins paintings of men rowing. Narrator David McCullough, who exhibits less passion than your average CPA, says Eakins lionized rowers as "heroes," though the paintings seem more idyllic than romantic.

We do get the impression however, from Michael Winship's repetitious script, that this Eakins was touched by greatness, in fact clobbered by it. He was "one of the greatest American painters who ever lived," says McCullough, and Rafael Soyer, who is "one of the greatest realist painters alive today," confirms that Eakins was "the greatest" American painter and that his "Gross Clinic" is "the greatest American painting ever."

And as we look at the painting, McCullough notes that "at its center is the greatest surgeon in the United States." This is the greatest load of flung-about greatnesses since the Oscar show. The whole point of television should be to show rather than merely to tell. The CBS "Sunday Morning" show does a much better job of celebrating artists and their work.

On to "that fateful afternoon" when that illustrious overreacher Custer suffered his well-deserved defeat. This sequence has a bit more dynamism. Still, the organization seems curious. The interesting thing about Custer is the way his image as "hero" fell with a crash in recent years, the way the statue crashed from the pedestal. But before McCullough gets to this subject, he drags us through a laborious account of the precise chronology of the battle, all the while admitting the whole truth can never be deduced about it anyway.

Much too late, Hollywood films on Custer are quoted and the subject of his fame turning to infamy considered. In a clip from "Santa Fe Trail," with Ronald Reagan playing a young brash Custer, Reagan quotes the old bromide, "He who hesitates is lost." These days, it may finally be dawning on Reagan that there is also something to be said for hesitation.

"Smithsonian World" is produced and directed this season by Rolfe Tessem, a talented young veteran of ABC News. He has seen and will see better assignments. It is stated on the program that Eakins, unrecognized in his time, sought solace "in the tranquility of music." Yes, and "Smithsonian World" is a program for those who seek solace in the tranquility of television. It's so tranquil, it snores.