A helicopter that looks as if it's dragging a large spider web is actually using the equipment to map out a grid of what is below the ground.

St. Lawrence Zinc, Balmat, hired Geotech Limited, Aurora, Ontario, which operates the helicopter and its dangling electromagnetic equipment, to reveal differences in geologic faults.

"You have to fish through them. It gives a signature and the potential for us to look for zinc," St. Lawrence Zinc General Manager Michael J. "Mick" Lawler said. "It gives us some potential targets."

The helicopter's back-and-forth route is primarily between Balmat, where there is an active mine, and Pierrepont, where the company's predecessor emptied out what was one of the nation's richest zinc deposits. The Pierrepont operation closed in 2000.

The survey is part of St. Lawrence Zinc's exploration for additional ore deposits. Although the mapping technique isn't new, technology to read the results keeps improving, Mr. Lawler said.

"Will we find something?" he said. "Time will tell."

The work is about 30 percent done.

The odd-looking equipment has a lot of people scratching their heads. The emergency dispatch center in Canton was swamped with calls Sunday from residents wondering what the craft was doing.

"It's nothing threatening, but it's kind of interesting," said Dennis J. Church, Canton, who watched the helicopter navigate a stiff wind Sunday as a storm rolled in. "It has this big netting hanging below."

John Bean, Canton, found out from the state Department of Environmental Conservation that the helicopter was probably conducting a geophysical survey but he wanted to know more.

"They fly fairly low," he said. "They're flying in a grid pattern."

Michael D. Corse, Pierrepont, was curious enough about the equipment to learn it had to do with mining.

"It's a pretty strange thing to see hovering over your house," he said. "It's flying over property and I was thinking, 'I guess I don't have any mineral rights.'"

Jon R. Montan, a planner with St. Lawrence County, took a picture of the helicopter Sunday as it flew over his house in Pierrepont.

"This is quite impressive," he said. "They can look a long distance underground."