Charles Snyder stood outside his house in the rain last week and looked across Trout Run to the new scar on the opposite hillside. He shifted the bulging chaw in his cheek, spat and said with no emphasis whatsoever, "Yeah. If they take out $8 million in gas, we get $1 million."

The "they" is Exxon U.S.A. which today is moving a drill rig to that scar, a graveled pad in Snyder's back pasture on the side of Great North Mountain less than 90 miles from Washington. On top of the ridge lies the Virginia state line, the North Mountain Trail and Big Schloss, a favorite mound of climbing rocks.

Even closer to Washington, in Frederick County, Va., just outside Winchester, Amoco Production Co. -- the domestic exploration and production arm of Standard Oil Co. (Indiana) -- is drilling a well that is expected to be 8,000 feet deep. Drilling was begun early in April and last week was below 6,000 feet, according to Dick Evans, Amoco's division exploration manager.

Amoco also plans three other such exploratory wells in the region this year, including one in Rockingham County, Va., for which a site now is being cleared and a road built. Harrisonburg is the county seat for that county. Amoco also has some acreage leased along Trout Run not far from Snyder's farm and will be watching Exxon's progress there.

For all his calm, these days there's an undercurrent of excitement coursing through Snyder, a big ruddy-faced man who raises about 40 cows and calves on the 159 acres that his father bought in 1940 when Snyder was a year old and are owned now by him and his brother.

"I'll go and sit on the bank and watch 'em drill," he said. "They can't keep me and my family away. may have to wear a hard hat, but I'll go and watch." And wait for the strike that could make him wealthy.

"People are all upset about disturbing that land," Snyder said. "They came up here from Washington and bought land. Now they're upset about disturbing that land, and they're upset about a pipeline going through. But they can't stop it. Exxon's like the federal government. It'll be built."

But only if Exxon, and its 10 percent partner, Consolidated Gas Supply Corp., find sizeable quantities of natural gas 9,500 feet down in the lower Knox dolomite. Last year Exxon and its partner spent nearly $4 million to drill a 16,000-foot well about 20 miles to the northwest. Industry sources say they were drilling a similar structure and targeting on the Knox just above a major thrust fault. They came up dry.

Drilling in the Eastern Overthrust Belt, as the zone of complex geologic structures running from New York and Vermont to Alabama is called, is no certain thing. It includes the Blue Ridge and much of the valley and ridge areas to the west. Drilling in the area is "a very high risk proposition," says Bill Hazlett, Appalachian district geologist for Chevron.

In addition to Amocco and Exxon, Chevron and a host of other oil companies big and small -- including Columbia Gas Transmission Corp., which supplies Washington Gas Light Co. with much of the gas sold to Washington customers -- are pressing the search in the Overthrust Belt.

Since Amoco made several strikes in Pennsylvania beginning in 1977 and Columbia Gas in West Virginia not long after, there has been a stampede to get land under lease. There has long been some oil and gas production further west in a band running from New York down through Tennessee. When Amoco made its strike, the companies realized that this was geographically the largest on-shore strike with oil and gas potential on land that was largely unleased.

That's no longer the case. Chevron has more than 20,000 acres leased in Giles County, Va., about 30 miles west of Roanoke. Gulf, ARCO and Texaco also have huge areas under lease in the Eastern Overthrust and plan to drill there.

Exxon and Consolidated have thousands of acres leased in an area that straddles the main Great North Mountain ridge where they are drilling. Seismic work has defined three anticlines -- an anticline is a fold in the rocks somewhat like an upside down batub -- that Exxon would like to test with a drill bit. One to the north and east is in the George Washington National Forest and Exxon would have drilled that one first except for some delay getting the necessary permits which now have been approved. That well, if ultimately drilled, could be in Virginia and, if so, would be Exxon's first well in the state, according to Don Langston, Exxon U.S.A.'s vice president for exploration.

The Overthrust Belt takes its name from the fact that great pressures from the east pushed older rocks over younger rocks to the westward. These so-called thrust plates, often many thousands of feet thick, now cover the younger rocks.

Exxon's target is the lower part of one of these thrust plates. The movement of the plate over the underlying rock may have created fractures through which gas could move to accumulate in the structural traps identified by the company's seismic mapping.

By no means are all of the people who have land along Trout Run upset at the prospect of the Exxon well. John and Mike Seddon, of 7202 Martins Court, Lanham, certainly aren't. Along with other members of the family including two other brothers, the Seddons have about 50 acres just to the south of Snyder which was purchased in 1978. Right after the land was bought, along came an Exxon landman to lease it.

Last week the Seddons were putting up new fencing on part of a 130-acre tract that lies east of the well site and between it and the top of the ridge. They have leased the land from Virginia Heishman of Manassas so they can fatten 15 steers for market in the fall.

John Seddon said Exxon representatives have said anyone with land within a one-half mile radius of the well will share in whatever it produces. The terms of the leases give the owners of the mineral rights a one-eighth royalty in any production. Moreover, if there is a job available on the rig, he'll snap that up, too, he added.

Some of the land along Trout Run still has not been leased. Three Years ago Snyder was paid a bonus of $3 an acre, plus the usual $1 an acre per year to sign. Now an Exxon landman based in Moorefield, seat of Hardy County, is out offering considerably more and the holdouts still haven't signed. Of course, in some of the really hot areas of Oklahoma, bonuses of $3,000 an acre or more have been paid this year.

Most land owners in the more promising spots up and down the Overthrust Belt are getting $15 to $20 an acre bonuses these days as the oil and gas companies strive to put together blocks of land before taking a chance on drilling. The late comers, with no chance to put together such blocks, are taking what they can get to make sure they don't have to tell their stockholders if a major strike is made, that the aren't in on the play.

The leasing activity has even moved east of the Blue Ridge, the highest risk of all. Many thousands of acres have been leased in recent months, in Bedford County and in the vicinity of Lynchburg. Other acreage has been leased in Culpeper, Madison and Rappahannock counties.

East of the Blue Ridge, the companies doing the leasing are betting that sedimentary rocks that could contain oil or gas lie buried beneath serveral thousand feet of older nonproductive crsytalline rocks. The presence of such sedimentary rocks was suggested less than two years ago by U.S. Geological Survey geologists partly on the basis of a seismic profile -- a line along which small explosive charges are set off or special equipment used to generate vibrations in the ground so that the resulting shock waves can be recorded to obtain significant information about underground geologic structures in east Tennessee and North Carolina. A second such profile will be completed this year running roughly from Staunton to Richmond and a third is proposed for next year in Alabama and Georgia.

Exxon's Langston, Amoco's Evans and Chevron's Hazlett were in full agreement on one point. The geology of the overthrust belt is so complex that its oil and gas secrets will not be unlocked until there has been much more drilling. For a variety of reasons, it's unlikely large quantities of oil will ever be found there or really mammoth deposits of gas. But with high energy prices, the incentives are there to continue to widen the search.