Considering that there must be thousands of birch trees in the sanctuary's 310 acres, the loot was well hidden - unless you knew the precise location: 44 degrees, 6.879 minutes north and 70 degrees, 10.391 minutes west.

Dave Hodgins and his son Brian found the treasure - called a geocache - in little more than 30 minutes, thanks to the coordinates, plus their Garmin Etrex GPS receiver and sharp eyes.

It was half-mile walk in the rain up to the highest point of the sanctuary and then another 100 yards bushwhacking through the trees. They found the white plastic Rubbermaid box next to a small-game trail in a stand of trees.

"It doesn't look that different from everything else around it," Dave said. "It's amazing how many people can wander by something like this without realizing it's right there."

Their prize? After sorting through plastic toys and trinkets, Brian selected a golf ball for his collection. He dropped a deck of playing cards and a CD of digital photos into the white plastic container before sealing it against the rain and tucking it back among the sticks.

It might seem like a lot of effort - hiking back and forth through the woods, braving ticks and poison ivy - for rummage-sale doodads, golf balls and Hot Wheels cars.

But for geocachers, it isn't about the prize. It's about the hunt.

"It's just another excuse to get outside and see some unique things," Dave said. "It's good exercise, fresh air and a lot of fun."

Geocaching has a national following and is getting more and more popular. It relies on a hand-held global-positioning system receiver to locate geographic coordinates.

People hide their treasures, usually toys and cheap collectors' goodies, in water-tight containers, such as a Rubbermaid box or an ammo can. Then they post their cache's location on the World Wide Web and wait for people to find it.

And they do.

An estimated 62,000 people in 183 countries have taken up geocaching. People have hidden more than 300 caches around Maine, including 36 within 25 miles of Lewiston.

Finders take something, leave a trinket of their own and sign the log. Mostly, they marvel at the views.

"You do get to see some amazing places that you wouldn't know about any other way," Dave said.

The game was impossible until the turn of the century. It relies on a network of satellites circling the globe and the Internet to make the information public.

The government-controlled GPS system has been around for years, but it had a built-in error to keep civilian GPS receivers from being too accurate. That error was removed by the Clinton administration in May 2000.

The game was born days later, according to geocaching lore. To celebrate the system's new accuracy, a man hid a bucket filled with prizes in the Oregon wilderness and fed the coordinates to his friends through the Internet.

Others began hiding similar treasures and posting their results on the Internet. In September 2000, Web designer Jeremy Irish started the Geocaching.com Web site and the game began to grow, picking up adherents around the world. The Web site now tracks caches hidden in Saudi Arabia, Australia, Europe, Japan and South Africa.

The game is free and open to anyone willing to register with the Web site, which now is run by a company called Groundspeak

Dave Hodgins bought his GPS receiver in 2000 soon after the system became more accurate. Originally, he used it to map all-terrain vehicle trails and to locate abandoned homesteads.

"I'd do the research, looking up old maps and then try and figure out their coordinates," he said. "These were old farms and buildings from the 1800s. It makes hiking a little more interesting."

He was looking for digital maps on the Internet one day when he stumbled upon the geocaching Web site.

"The next day, I went out and found my first geocache," he said. "I looked and found one that was right by my house, and I was hooked."

He has since found 122 caches, most of them around his home in Clifton in Penobscot County and most were found with Brian. The two go by the handle "Brdad" on the geocaching Web site.

Brian, 15, collects golf balls from the caches. Dave prefers unique items and one-of-a-kind collectibles, such as handmade wooden nickels and carvings. In their place, Dave likes to leave copies of his Maine Sights CD, a collection of digital photographs he's taken around the state.

Dave has hidden four caches of his own, relying on devilishly clever clues to make finding them even more difficult. His "You Sank My Battleship" cache requires finders to visit as many as 25 different places around Bangor, answer questions and do math to figure out the final hiding place. He tested the clues himself, and it took him two hours to solve the puzzle.

"I knew all the answers and it still took me two hours," he said. "With luck, I guess someone could find it in three hours of hard looking. Most have to visit it a couple of times to figure it out."

Geocachers in other states have formed clubs and organizations to promote the game. They meet, sponsor park cleanup days and answer questions from curious public officials and novices.

Maine doesn't have that kind of group yet, but one could grow out of a barbecue scheduled for Aug. 23 in Augusta. Maine geocachers are invited to show up at the park for a day of cache searches, cookouts and swimming.

The invitation, posted on the Geocaching.com Web site, doesn't give an address or driving directions. Just the coordinates: 44 degrees, 20.684 minutes north and 69 degrees, 39.190 minutes west.