"Sometimes, when I get over here early and sit watching the sun rise, it's almost kind of spooky - so many generations watching, saying I'd better give a good account of them. . . Once you disturb what they've left, you can't put it back the way you found it - it's a big responsibility."

When Mike Humphries, county archaeologist of St. Mary's County on Maryland's Western Shore, talks of "many generations" looking over his shoulder, he's not kidding: This bluff above Breton Bay, on Maryland's Western Shore, has yielded traces of every culture from the paleolithic to the present.

More than seven millenia of Indians, including three woodland eras, settled here, as did colonists from the 17th century on. In one single dig, barely eight feet by a dozen, they've found pieces of Indian wrapped pottery, English delftware, Indian scraffito and Chinese polychrome porcelain - all dating from the 17th century.

The site, somewhat grandly titled Potomac Archaeological Park, is part of a tract of several acres lent to the county for the next 200 years by Abell Clarke, who lives almost next door. It's being worked by the George Washington University and the St. Clement's Island / Potomac Museum, and though they don't want you to go around picking things up, you can watch the pains-taking students collecting artifacts, marking and plotting their locations, sifting the soil and generally tracking down who came this way, and when, and what they did while they were here. If you want to know more than the signs posted around the place can tell you, tours and tour guides are available, as well as a brochure that, Humphries laments, was printed the week before the paleolithic arrowhead was found.

"Actually, it was probably a hunter who just lost it as he was passing by," the archaeologist adds.

But as you sit in the park's picnic area, looking over the bay - and mentally blotting out such recent improvements as tne houses across the water, a brightly colored buoy, Abell's Wharf and the gravel pit - it's easy to step back 300 years or so and be an Indian watching colonists arrive, or a few generations more and be an Indian blissfully unaware that colonists lurk over the horizon.

Then, if you haven't brought your lunch, you can drift down to the little bar and restaurant at Abell's Wharf for some surprisingly good Mexican (yes, Mexican) food - a meat-and-cheese burrito, for example, or just "el munchos" that range from $1.50 to $2. Dinners run $2.75 to $5.25, except for the $8.50 steak-and-quail special.

Another feature of the little bar is a large map on one wall, showing Abell Clarke's plan for developing the point. Pick out your lot now - or, if you really take the long view of things, negotiate an option for a lot up on the bluff after the 200-year archaeological loan runs out. In a county that runs to 300-year-old buildings and 400-year-old trees, that might even seem a reasonable plan.

Even with time out for lunch, though, the archaeological park won't fill your day, which is a good thing; for there's a lot more to see in St. Mary's, the "Mother County of Maryland," than the fields of 'bacca it's known for.

For starters, you might drive around to the St. Clement's Island / Potomac Museum, maybe 15 miles away, and see more of the artifacts unearthed at the archaeological park as well as exhibits relating to the farms and watermen of the area. Then, if you've planned ahead and chartered a boat trip (groups of five or more), you can set off from the museum's wharf and go out to St. Clement's Island, where the Maryland colonists landed in 1634. The tour of the island's wildlife and historical exhibits lasts about two hours and costs $3 ($1 for children under 12), which includes the boat trip and, back on shore, admission to the museum. The museum alone is 50 cents, with children under 12 admitted free.

One of the most fruitful stops in the county is "the old white house" on the campus of Charlotte Hall School, now used as the county's information center. Brochure-collectors can run amok here, and a pictorial map of the county, which you can carry away free, lists no fewer than 23 places of interest - including the only federal monument to Confederate soldiers (at Point Lookout State Park, where some 4,000 Confederate prisoners died during the Civil War).

If reading of all these choices exhausts you, a restorative is right across the road from the information center: "Ye Coole Springs of St. Marie's," which became noted for their healthful qualities at the end of the 17th century - so much so, in fact, that the country's first sanitorium was built there to take advantage of their allegedly curative waters.

There's no record that the Indians ever made use of the "Coole Springs'" waters, let alone thirsty paleolithic people. But who knows? Maybe the archaeologists just haven't gotten to the springs yet.