John Phillips is happiest here, in his favorite classroom. Here, among the trees and on the water, he fuses teaching and the great outdoors into one. One day-long lesson under one boundless sky. One eight-hour journey down one historic river.

This is his fourth summer leading educational canoe rides on the Potomac River, and today, Phillips nods approvingly at the shallow water and warm air--ideal conditions for his "Indian Summer on the Potomac" trip.

The trips began in 1995, when Phillips, an author and historian from Leesburg, took 20 schoolteachers on a tour of historical sites along the Potomac. From there, word spread and demand rose. Newcomers wanted to get to know the area. Old-timers wanted to learn the local history they never knew. He now offers trips almost every summer weekend and several times in early fall.

"Just being out in the fresh air, gosh, how can you beat it?" Phillips said. "I really miss being out on the ocean all summer long, like I did when I was a kid. But this is a pretty good replacement."

Ten people took Saturday's trip with him, exploring an eight-mile stretch of the Potomac from Point of Rocks to the tip of the Monocacy River. Young and old, they were all Phillips's students for the next eight hours.

Les Horn, a Reston physicist, took the same trip more than a year ago and is back. This time, he wanted to share the experience with his two teenage sons, Tom and Andrew.

Valerie Weisman and Ed Fleischer, an Ashburn couple, signed up after seeing a small ad in the paper.

Judy Fincher, of Sterling, always has liked to spend her weekends outdoors and jumped at the chance to join the journey.

Phillips asked his friend Laura Larson, of Alexandria, to come along because she had never taken the trip before.

And Breega Barbree, of Loudoun County, went with her husband, Russ Martin, and sister, Catherine Barbree, who was visiting from Florida. Barbree wanted to entertain her sister with something different, something besides visiting museums.

"I've lived here for 10 years, but I've never been out here on the river," Barbree said. "So this is lots of fun."

Phillips armed the group with only the essentials: canoes, paddles and life vests. The rest is strictly bring-your-own. Sweat pants and sneakers for hiking, bathing suits for swimming, water for drinking and sandwiches for eating.

After a safety lecture, the group broke up into five teams of two. Experienced paddler in the stern, the other in the bow. Shortly after 9 a.m., they set out for the first stop, a small cove on Conoy Island, known on modern maps as Heater's Island.

An Inlet to the Past

An hour later, the canoes pulled into the cove, a narrow inlet that paddlers usually would miss. Arms and shoulders were still fresh. Paddling, at this point, was great fun.

Boats were dragged onto the landing. Off come the sandals and shorts, on come the sneakers and sweats.

Phillips's students plopped down on logs near the beached canoes.

During the 17th century, he began, tribes from three Native American cultures--Algonquian, Iroquois and Sioux--lived in the area. Through his travels along the Potomac and around the Chesapeake, English settler John Smith discovered and chronicled their complicated rivalries, blood feuds and alliances. Battles over trade routes were common among three local Algonquian groups--the Potowomacs, the Anacostins and the Piscataways. The area the paddlers were about to explore was sort of an Indian no-man's land because it acted as a buffer zone for the three tribes.

The most powerful were the Iroquois, so dominant that much of the Indian world lived in fear of them, Phillips said. During the late 1600s, the Piscataways moved to Conoy Island from their ancestral home in what is now Maryland, partly at the suggestion of the Iroquois, who thought the Piscataways and the Europeans lived too close to each other and were too friendly. Conoy, in Algonquian, means "far, far away."

Before the group set out for the old Piscataway village on the island, Phillips gave members a short lesson in flora.

"This is fireweed right here," Phillips said. "See the serrated edges and the seed pods? You don't want to touch this stuff. . . . But there's a natural analgesic that usually grows nearby--jewelweed, see, that's some over there."

Weed wacker in hand, Phillips led the group along a rough trail. He looked like President Clinton in jogging attire. He walked quickly among the old, tall trees that grow all over the island, stopping in an area where the trees are suddenly skinnier, younger. It is an area that was obviously completely cleared at one point for civilization. The group was silent for a moment, their eyes scaned the surroundings. This is where the Piscataways once lived.

Phillips picked up his lecture: The Piscataways moved to the island in part because the Europeans in the Maryland colony had taken over part of their tribal hunting lands, plowing them for crops.

"It was a case of suburban sprawl in the 1600s," he said.

The Piscataways lived on the island for about 25 years starting in 1698. The English were not happy about the move, because the tribe had been friendly and served as an early warning system about other hostile tribes roaming in the area. But after more than two decades on Conoy, the Piscataway population was reduced by disease, and a 1722 English treaty setting boundaries for the Native Americans drove even more of them off the island. Some headed back to their ancestral home in Maryland, some intermarried with the settlers, and others moved into the Susquehannock Valley.

A Land Time Forgot

The next leg of the trip was shorter, around to the middle of Conoy. The landing is rocky, unlike the sandy shore. Phillips explained that most of the rocks are river rocks, which the Indians carried in from the water.

As the group neared the center of the island, they caught glimpses of an old, abandoned house through the trees. The walls seemed moments away from falling down, the roof at the point of caving in. The house has been empty for about 50 years, Phillips said, and its only visitors are his occasional students.

Nearby are rusty remnants of farm equipment during a flood early in the early 1950s. An old plow. A hay loader. A wheat drill. They are reminders of the farmers' desperate escape from the island.

Farmers came onto the island shortly after the Civil War. The Heater family owned the island for most of Conoy's incarnation as an agricultural outlet, but toward the end, they rented it to tenant farmers. The island now is named for them.

Near the house is a big, red barn whose walls look even less stable. Only a few people were adventurous enough to go in with Phillips, who joked, "If you hear a large noise above you, move out of the way!"

"I used to have a barn like this," said Larson, who stayed outside. "I bet there are tons and tons of bats in there. When I was a teenager, I made a room for myself at the top of the barn so me and my friends could smoke. We were brave enough to endure those bats to smoke cigarettes."

As the group hiked back to the canoes, their gait was a little slower, their legs a little wearier, the day a little hotter.

At the landing, they tucked gratefully into a morning snack.

A Key Crossing

The stop at Francis Awbrey's landing was quick. The Indians regularly used this point to cross the Potomac, Phillips said, and later, colonists established it as the ferry crossing for people traveling north and south. It was the crossing for the original Carolina Road during the 1730s.

Next stop: Noland's Landing, where bald eagles frequent a stand of dense trees. But a solo, circling bird turned out to be a vulture.

Moments later, he spotted another bird, flying alone. "Oh, right there, that might be one! I can't tell. Maybe . . . "

The ride from Awbrey's to Noland's Landing was long. Arms tired, shoulders grew. Time for lunch and a swim.

"This is where [George] Washington stopped to eat lunch," Phillips told the group.

Not only that, he said, the site is probably one of the most significant historical places in American history. The ferry crossing began about 1740 and was so important to the Continental Army during the American Revolution that Washington posted an officer there permanently to receive and manage supplies. British troops who surrendered in New York were marched south and crossed here in the winter. And the Marquis de Lafayette, the French general, got reinforcements in 1781 from a Pennsylvania brigade that crossed here.

The crossing was a hotbed of activity, with its own post office, tavern, bootmaker and blacksmith. Now it is simply a peaceful place to rest.

After lunch, Andrew Horn, 13, swam for a while. He then found a tire hanging from a tree. He climbed on, and his father pushed--the higher the better for Andrew.

Judy Fincher was relaxed as she surveyed the beautiful water, the gorgeous day. Maybe too relaxed.

"I need a nap," she said.

The Fish Trap

Somewhat refreshed, the group paddled on to Phillips's favorite spot on the river--the fish trap. The river had been unusually still all day, but here, the current accelerated and carried the paddlers along.

Native Americans caught fish by building a stone wall in a V-shape downstream, Phillips said. So the fish would be forced to come out of one small spot on the river, where waiting Native Americans would scoop them from the river.

Tired Paddlers

The last leg of the trip was the hardest.

Dripping with sweat, the paddlers pulled into the Monocacy boat landing not a moment too soon to suit them and piled into the bus that would take them back to Point of Rocks.

"Did everyone have a good day?" a voice in the bus asked.

The paddlers had just enough energy left to answer.

"Yeah."

"Yup."

"Yeah."

For information about the trips, call 703-771-1770 or visit www.rivertrail.com

CAPTION: Canoeists near the end of a day-long "Indian Summer on the Potomac," a journey conducted by historian John Phillips.

CAPTION: Les Horn and son, Andrew, canoe along the Potomac. Horn, a Reston physicist, took the trip more than a year ago and this time wanted to share the experience.

CAPTION: The eight-hour, eight-mile trip down the river for "Indian Summer on the Potomac" combines the educational--learning about the history of various stops along the waterway--with the recreational.

CAPTION: Two centuries ago, Continental Army troops might have marched through this spot at Noland's Landing. Andrew Horn, 13, finds it an enjoyable spot for after-lunch fun.

CAPTION: Ryan Barker, of River & Trail Outfitters, paddles near Point of Rocks. Below, an unexpected guest.