Priming the pump at Yosemite museum

Two children, sporting newly purchased Yosemite National Park T-shirts, vigorously shove an antique pump handle up and down. ''In 'Little House on the Prairie,' water comes out,'' the boy complains to a National Park Service guide impersonating Elizabeth Hodgdon, who lived in this Aspen Valley log cabin a hundred years ago.

''Let me show you how to prime it,'' offers ''Elizabeth,'' who dresses in floor-length, long-sleeved calico.

When the water flows, she turns to extract an apple pie from the oven and put in its place the rising loaves whose yeasty fragrance already permeates the cabin. The children's parents and grandmother sniff the tantalizing aroma appreciatively.

Like many other visitors to Yosemite Pioneer History Center, near the park's south entrance, this touring family is participating in living history, learning the realities of homesteading a century ago in the American West.

''Our family has been very comfortable up here in our summer ranch since we built it in '79,'' the costumed guide informs them. ''But we may not be here much longer if that John Muir fellow gets his way and persuades Congress to make Yosemite into a national park.''

''It's already a national park,'' protests the boy, pointing for confirmation to the Half-Dome, the park's official logo, on his shirt.

''No, sir,'' the pretend-homesteader retorts as she stokes the stove's firebox with another pine log; ''this area was ceded to the State of California in '64. President Lincoln himself signed the bill. And now homesteaders like us, who've proved up on our land and filed our deed all legal, are threatened with the loss of our livelihood. How are we going to feed our families if we can't come up here to graze our cattle?'' she demands of the touring family, who by now have clustered around her kitchen table. ''Are you gonna let the government deprive us of our land?''

Brows furrow as the visitors wrestle with this question. The guide has drawn them into the impromptu drama; the debate over federal land policies mounts.

Ranger Michael Adams, supervisor of the summer program at the center, admits this kind of museum interpretation doesn't always work. ''I've seen some visitors intimidated by this - and I've seen some get inspired. Depends on the visitor.''

Like the pump in the Hodgdon cabin, visitors need ''priming'' to get the most from the living-history experience. The center provides an introductory slide show which explains the concept of living history and gives examples of the kind of conversation visitors can expect in the six cabins, each moved to the center from a different part of Yosemite and each representing a different era in the park's history, from about 1875 to 1915.m