Here I am, getting rid of my used-up Slim-Rite Wundertip felt pen and standing over the wastebasket ready to throw the thing in like a dart-when I stop in my tracks and tell myself, Wait a minute. Did I think this was nothing but a piece of trash? Jetsam from my frantic career? I am holding in my hands here a nugget of history.

Last fall a team of archaeologists did a dig at the Mall location of the future National Museum of the American Indian, a $110 million building that will stand just east of the National Air and Space Museum, and they unearthed a lot of trash. The National Historic Preservation Act requires that every federally funded building must first have its site vetted for possible impact on cultural resources, which means it has to be checked out for artifacts of bygone civilizations.

It is a useful policy. The practice of looking where we dig has had payoffs for the Smithsonian even when something other than early civilizations have been involved. A dozen years ago, at a construction site near Largo, Maryland, work was delayed for a few days when a giant bone pulled from the mud proved to be the rib of a mammoth. Plunging up to my knees in the mud, I reported the find for the Washington Post. And by the time Smithsonian paleontologists had examined the find, and the press reported it, we all knew a lot more about mammoths.

And I remember back in 1984 when a 29,000-year-old cyprus log was pulled from the hole that would become the underground complex of the Arthur M. Sackler Gallery and the National Museum of African Art. Once again we got a chance to learn a little something, that time about Washington at the beginning of the last ice age.

The Mall site for the Indian museum is a strip of land between the Air and Space Museum and the U.S. Botanic Garden. Today it is open greensward-a nice place for a game of volleyball, with a stunning view of the Capitol. But in the last half of the 19th century, and as late as 1928, it was a residential neighborhood whose ambience is suggested by the name of a dirt roadway that ran behind the houses: Louse Alley.

It was not a high-rent district, and probably most residents were more or less transient. A Washington Gas Light Company tank loomed over the street, alongside the E. N. Gray & Co. Foundry and the Taylor and Low Stone Yard. Living in these narrow houses were immigrants from Europe and some African-American families. There was no sign of the area's 17th-century inhabitants, the Conoy Indians, a rather sedate group of Algonquian farmers who apparently didn't want to settle on what was then marshland.

The search team dug as deep as eight feet through soil that had been brought in to fill the marshland when Tiber Creek (which ran roughly along today's Constitution Avenue) was drained and channelized in 1815, and they found "oyster shells, 400 pounds of oyster shells!" according to Donna Seifert, the project manager for John Milner Associates, urban archaeologists, planners and architects.

I don't know, maybe oysters were cheap in those days, but 400 pounds of oyster shells means a lot of oysters. It sounded to me as if someone must have had a grand party out there. "Oh no," Seifert says. "We looked on the map and found there had been an oyster house on the corner."

There were also many bucketfuls of crockery shards, blue pottery from Britain, kitchenware, antique beer bottles, medicine bottles, animal bones and a couple of dolls much the worse for wear. All these items have been taken to the Milner lab in Alexandria, Virginia, to be analyzed to determine, for example, what companies made the discarded dishes and bottles. A report is due this summer.

The archaeologists noticed that residents tended to pile up their refuse at the back of their yards, occasionally shoveling dirt on top. And since most of the houses had no running water or bathrooms, "we were hoping to find outhouses," Seifert says, "because a pit of any kind, a cistern or even a well, when it's abandoned, gets filled in relatively quickly with garbage. This makes it a sort of time capsule. But unfortunately the locals used only box privies, the kind with removable drawers for easy cleaning."

Too bad. Ah well. One problem with things that have been scattered about a yard and not neatly collected in a pit is that you often can't tell for sure whether they all really belong together in time and space.

I have seen an old photograph of Louse Alley, probably in connection with outraged articles about the neglected neighborhoods of Washington, showing rows of tumbledown wooden and brick buildings only a few blocks from the Capitol dome.

Back in the 19th century, Louse Alley couldn't have been any more charming than the rest of Washington as described by a French visitor in 1840: "the inhabitants all own cows and pigs, but no stables, and these animals wander about all day and all night through the city . . . the women milk their cows on the sidewalk and sprinkle the passers-by." There was no organized garbage pickup in the city until 1863, and even then, I suspect, Louse Alley may not have been the first neighborhood to have it.

But I am fascinated with the idea of winkling history out of trash, or more to the point, out of the things we take so utterly for granted that we never give them a thought. All we know of many of the very earliest cultures comes from what archaeologists have been able to deduce from the middens. Why shouldn't it work for modern cultures? It is precisely the things we don't pay any attention to, the everyday implements-the toothbrushes and spoons and bottletops, the givens-that often prove to be the clues to a particular society.

The mere discovery of a carefully laid out ancient grave in, say, Germany can produce a variety of insights and suggestions: a belief in an afterlife, for example. A bell-shaped, handleless drinking vessel may be found in the grave, causing the experts to slap their foreheads in amazement: the Beaker folk were here! Find enough beakers and a startling new picture of Bronze Age trade emerges, a network covering all of Western Europe. The smallest detail may contain the essence of our own time. A toothpick discarded today might give an archaeologist palpitations in the 22d century.

What sorts of secrets the denizens of Louse Alley may have harbored, I have no idea. The original wood-frame houses were torn down in midcentury and replaced with brick row houses, and then the whole area was leveled in the 1930s. In World War II a temporary office building was erected there but removed about 25 years later. We do know that most of the people were short-term renters and that a few of the women who lived there at midcentury described themselves as prostitutes by profession, which was one of the entries listed on the census forms of the day. No big secret, obviously.

What clues will we get from these poor shards and bottles? It's astonishing how much a thinking person can make out of very little.

Take animal bones.

"If you look at the bones closely," says Theresa Singleton, from the anthropology department of the National Museum of Natural History, "and they are cut into short pieces, show slice marks or are extra brittle, then we might say they were boiled in a stew. "Then you check out the ceramics," Singleton adds, "and if you see mostly bowls, you know those people ate soups or stews a good deal of the time."

Not many steak knives to be found on Louse Alley.

But how do we tell the African-American poor from the Irish, German and French immigrants? "The hard part is figuring out whose trash we're looking at," says Donna Seifert.

"What you need is quantity. You need enough samples of consumer strategies to reach a conclusion. Now, medicine bottles can tell you something. At another site, to give you an example, we found that different ethnic groups tended to use different patent medicines," Singleton explains.

There is a certain amount of discussion, not to say controversy, among professionals over this sort of period research. It was only a generation ago that archaeologists began focusing on the debris of ordinary people from the 19th century. What does archaeology offer that's not in historical documents?

A lot, it seems to me, and if you think I don't see this Slim-Rite Wundertip felt pen in a new light, you haven't been listening. I mean, this is not just a pen, it is an artifact. Furthermore, the ink is, or was, violet, which I failed to notice when I bought it.

Who knows what they might make of it in the 22d century?