LANCASTER -- To think like an American Indian, it is said, you must walk in his steps.

Roberta Strickler, Lancaster Intelligencer Journal via AP Paul Nevin, right, uses a wet sponge to outline faded carvings in a rock on the Susquehanna River on Aug. 13 in Conestoga. Eighteen people from Lancaster, York, Dauphin and Perry counties climbed onto Big Indian Rock in the center of the Susquehanna to wonder at markings, called petroglyphs, left by Indians between 800 and 1,000 years ago. Click photo for larger image.

At noon on a Saturday last month (the hottest day this year), 18 people from Lancaster, York, Dauphin and Perry counties climbed onto a very bare rock in the center of the Susquehanna River to wonder at markings left by Indians between 800 and 1,000 years ago.

Perhaps a thousand markings, called petroglyphs, were carved into rocks of the Susquehanna, between Columbia and the Maryland line, over time. About 300 glyphs can still be found in the river, if you know where and how to look at them.

This group went to Big Indian Rock. Its flat surface is 60 by 40 feet across, with not a tree nor a blade of green growth. In the center is a fire bowl, but whether it was created by American Indians, later American shad fishermen or simply the weather, is just one more question offered by this old rock.

A few answers were provided by the guide, Paul Nevin, of Accomac, York County. Mostly, he raised more questions.

Nevin, who earns a living restoring houses, has earned a reputation for careful research of the petroglyphs that remain below Safe Harbor Dam. "His contribution is amazing, in that one individual has brought these glyphs to our attention, recording them in digital format and with exacting details," said Steve Warfel, who is senior curator of archaeology at the State Museum in Harrisburg.

"Indians liked to gather where water, sky and earth meet," Nevin said. "The People," as Indians referred to themselves, observed nature as the "mother" with respect. They would never deface "a grandfather," a rock, for anything less than a spiritual or important meaning, he believes.

The People observed nature as if they were a part of it, and seem to have recorded constellations of stars. They showed an understanding of the travels of the sun and the moon, the equinox and solstices, as we know them. They showed the identity of animals by distinctive tracks or features, such as the hump of a buffalo, much as many people today would describe objects through caricature.

When artifacts are disfigured, stolen or removed, even with good intentions, the original orientation of the artifact, such as east/west, north/south, is gone and there are few clues left to understand.

Our Saturday group was outfitted with river guide, lunch and kayaks by Shank's Mare at Long Level. We put in the river below Safe Harbor Dam and paddled upstream about a mile to see these symbols carved into rock.

This area is one of a few short stretches of the Susquehanna that still look a bit like the shallow, rocky, wide expanse of river that long served as the chief transportation corridor from the Chesapeake Bay into New York state. It was Iroquois and Algonquin territory when the first Europeans arrived in the 1600s, began trading and changed the culture of the American Indians along this corridor.

This long native history is marked here in different symbols, worked by hand using rock tools against the hard mica schist.

Nevin has devoted the past 25 years to the project of finding, defining and mapping these mysterious carvings.

"Our ability to interpret them is very limited," Warfel said. "We have no living surviving populations to carry on the oral tradition.

"We do know now that this rock art is not some kind of graffiti. It has symbolic meaning and carries some elements that are found throughout the world."

Nevin has spent many hours searching for petroglyphs on these rocks. On just one of these rocks, he said, there are 100 glyphs. Sixty of them came later, maybe marks made by early Europeans, or the initials of a fisherman, or a large dove carrying an olive branch, signed and dated in the 20th century.

This modern sort of "rock art" stopped "fortunately," Nevin said, about 1970, when a protective awareness arose of the fragile and important nature of the glyphs.

Nevin seems to have adopted the Indian attitude toward the earth: that there are evil forces and friendly forces and that nature embodies both qualities. Presenting a friendly face is an instinctive way of neutralizing evil when meeting an enemy. The enemy of an Indian's petroglyph, in today's terms, may be a duck hunter looking to place the solid foundation of a duck blind on a carved rock.

Such defacement of elements of the river can bring a hefty fine, Nevin said.

"Instead, we have been able to enlist the aid of the hunters. They help us by transporting other researchers in their boats. Friendly hunters, by their presence, also help to dissuade people who want to add their marks or to carry away souvenirs.

On this hot summer afternoon, Nevin waits until the group becomes, so to speak, a part of the rock. We are hot; we have taken to the cool river water; we haven't really "seen" any petroglyphs.

He walks around the rock, stopping when he sees his old friends. He soaks a sponge and uses the water to outline the faint figures. As the afternoon comes to us, the angle of sunlight changes and more and more glyphs show themselves.

"It was surprising," said Emily Burt-Hedrick, of Perry County. "At first, you couldn't see them in the rock. After a while, I moved and looked from another angle, and there they were."