A pile of bones and bottles dug up the other day at historic Fort Mason has a tale to tell of the Civil War, medicine and the way San Franciscans lived as many as 150 years ago - but it may take months to decipher it.

In the meantime, archaeologists and historians are just thankful that the cache of 19th century treasure lay undiscovered for more than a century, buried just beneath the surface at a popular tourist site within view of the Golden Gate Bridge.

"It is a surprise, but really it's just history playing with us," said Gladys Hansen, curator of the Virtual Museum of San Francisco. "If we didn't have something like this come up and really tax our minds, and make us look back, we wouldn't have as much a sense of history.

"Everything we can get a hold of from the past hopefully helps us understand the people and what they faced, and how they handled their predicaments," Hansen said.

Work crews clearing soil contaminated by lead paint stumbled on the first of the artifacts Oct. 25, said National Park Service spokeswoman Alexandra Picavet. The soil was around the foundation of a historic building being refurbished, she said - federal law intended to prevent looting prohibits her from revealing the location.

"The bones and artifacts were just a couple of feet underground, and as soon as the archaeologist we had on site to monitor the work was notified, he stopped all of the work," Picavet said.

She said more bottles and bones turned up throughout the week. All of the historic items had been removed by Friday.

"We will now start the arduous process of sifting through archival information, historical documents, books, maps and photos, and of course the evidence that was found on the artifacts, to try to come up with a reason what we found was there," Picavet said.

Park officials are pretty sure the materials date from the early 1860s, when Fort Mason was built to defend the coast during the Civil War.

The fort, which sits between Fisherman's Wharf and the Golden Gate Bridge, was an Army base until the 1960s. The Park Service took it over in 1972, and today the fort draws tourists to view the old military facilities, and historical buildings are used for community programs and events.

Fort Mason also used to have a hospital, and examining the artifacts and remains could help historians better understand the medical practices of the mid-19th century, Picavet said.

It appeared some of the bones were cleanly cut, indicating possibly that they were amputated limbs, she said.

The bones may have come from as many as 20 people, she said, and scientists believe they are not American Indian remains. Several bottles and buttons were also near them.

"They were mostly medicinal bottles, though they did find one hair tonic bottle that is quite lovely with flowers on the label," Picavet said.

Once historians are done with their examinations, the artifacts will be cataloged and stored in the Park Service's historical collection.

Officials haven't determined what to do with the bones yet.

"We don't know how significant any of these things are right now," Picavet said. "It will probably take months to go through everything."