Exhibit B-40/40 appears to be a jar of black earth, but if you tilt it you can see small silvery globules and rivulets of mercury rolling back and forth in the dirt.

The spot this dirt came from is so contaminated with the toxic metal that it allegedly contains more mercury than any place on earth outside a mercury mine. A mercury processing plant made fungicides and mercury compounds here for years under a series of owners prior to 1974, slopping as much as 4 pounds a day of the metal onto the floors and washing it into the swampy field out back. Eventually much of it drained into Berry's Creek and now sits in the sediment on the bottom of the stream.

The jar can be found in a file cabinet along with mountains of documents at the New Jersey Superior Court at Hackensack.

Nearby, as more evidence in the tangle of lawsuits that have sprung up around this case, are several cardboard boxes of dirty, broken bottles, plastic jugs and grimy trash from the field, all enclosed in tightly knotted plastic bags.

"One of the expert witnesses told me we shouldn't be breathing the air around that stuff so I ordered the bags put on," said Judge Sherwin D. Lester.

Judge Lester will rule sometimes next spring on what kind of cleanup will take place at the Wood-Ridge site and who will pay some or all of the estimated $6 million cost. His decision could set precedents for dealing with the growing number of old hazardous waste sites that are being discovered almost daily, their sources and owners in a fog of corporate back-passing.

"If there are 1,000 hazardous waste sites around the country - and that's not an unreasonable figure - and if we assume $5 million to clean each one up, and that's not unreasonable either, then that's $5 billion that has to be found somewhere," said Steffen Plehn, head of the hazardous waste program at the Environmental Protection Agency.

The EPA last week estimated that 32,000 sites nationwide may contain hazardous wastes in form of pesticides, acids, caustics, nuclear residues and other chemicals, many of them carcinogenic, from some 425,000 companies. An estimated 30 to 40 million tons of hazardous stuff is produced and is disposed of every year, up to 90 percent of it in ways we will probably regret later, the EPA said. "We Can't Be Too Careful"

MERCURY in its various forms, for example, can be nasty stuff, causing blindness, nerve decay, birth defects and death. The New Jersey Department of Environmental Protection wants 3,000 feet of Berry's Creek to be dredged out and the entire 40-acre Wood-Ridge field to be blacktopped and then surrounded by an impermeable wall reaching 20 feet underground to a natural layer of clay.Along with a monitoring program, the cleanup would cost $6 million.

"This site is the major source of mercury contamination in the Meadowlands and everything else is insignificant by comparison," said Ronald P. Heksch, deputy attorney general of New Jersey.

He does not try to present Berry's Creek as some kind of pristine brook full of jumping trout that must be saved from mercury. Much of the swampy, tidal area called the Jersey Meadows has been grossly polluted for decades from dozens of industrial sources, and there have been no oxygen and no fish in Berry's Creek as far back as anyone can remember. That is one of the complications.

Heksch cannot produce a horror story of dead or dying people or hundreds of fish belly up in the water as evidence of damage, but must rely, he said "on the potential for what could happen" because of the mercury now in the ground and in the sediment of the stream.

Two miles downstream from the Wood-Ridge site is the new Giants' stadium and sport complex, built on mercury-polluted land. Further along is the Hackensack River, which flows into New York harbor. None of the murky water is now used for drinking. "But when the stream gets cleaned of other pollutants and the fish begin to come back, they will spend more time here and will stir up the bottom and pick up the mercury," Heksch said.

"We take the position that we can't be too careful. There are a million ways for the stuff to leave the site."

Much of the 50 days of courtroom testimony has involved experts arguing about the relative dangers of one kind of mercury over another, the total tonnage of the metal present in the field and the chances of it moving downstream. These issues of quality and technology recur in virtually every hazardous waste case nationwide. Even when all sides agree, as they do here, that there is in fact a pollutant present, it may still be hard to fix the blame and harder yet to get the cleanup paid for.

In many cases the disposal was perfectly legal at the time it occured and in others the firms have vanished or been absorbed in a corporate merger.

Some examples cited by EPA's Plehn:

Salisbury Laboratories, a veterinary pharmaceuticals plant in Charles City, Iowa, has been dumping arsenic and other chemical sludge onto an 8-acre site since 1953. The arsenic is now leaking from the landfill into the Cedar River, a major waterway, and the estimated cost of digging up the landfill and moving it is $30 million. But the company's total net worth is only $5 million. Who pays for the repairs?

Pesticide chemicals in the water supply of Hardeman County, Tenn., are identical to those in 350,000 leaky drums of waste that the Velsicol Chemical Corp. buried nearby from 1965 to 1972. There is no other apparent source for the toxic stuff, but even if the drums are the cause, burying them there are perfectly legal when it was done. Should Velsicol have to pay?

The area around New York's Love Canal has been declared a federal disaster area with the discovery that at least 82 different chemicals, including radioactive and carcinogenic compounds, are simmering in leaking drums in a dump that the city of Niagara used legally for 25 years. At least nine chemical producing companies used the dump before it was deeded over to a school district, allegedly against the companies' will, and the chemicals are turning up in basements and back yards.Cleanup may cost $8 million plus whatever it takes to move about 235 families to new homes. Who will pay? Regulation by Hindsight

ON TOP OF all these cases is the feeling that pollution control watchdogs should have spoken up earlier when the dangers were first realized. Robert M. Wolf, the New Jersey realtor and developer who now owns part of the Wood-Ridge site, insisted he knew nothing about any mercury on the property when he bought it for $90,000 an acre in 1974 from the Ventron Corp., and if he had, "I wouldn't have touched it with a 10-foot pole."

The contamination was first documented when Wolf began tearing down the old chemical processing plant in order to build warehouses to rent. Wetting the structures for demolition produced a silvery runoff and environmental experts soon overran the place. They found concentrations of mercury up to 123,000 parts per million in the surrounding land and in the stream bed. Nationwide background mercury levels rarely exceed one part per million, and EPA limits mercury levels in drinking water to two parts per billion. A dose of 160 parts per million can be lethal.

Under some state laws, Wolf could be liable for cleaning up the mercury on his portion of the area simply because he now owns the property. But New Jersey wants him merely to be responsible for maintaining and monitoring a containment tank it required him to build under one of his ware-houses for the 10,000 cubic yards of topsoil he was forced to scrape off the site. The various requirements, Wolf said, have cost him more than $2 million.

"Ventron ought to pay for this," he said. "They put the stuff there and they can handle the expense of removing it."

Ventron, a subsidiary of the chemical and aerospace giant Thiokol Corp. of Beverly, Mass., and Newton, Pa., has maintained in turn that any mercury emitted during its period of ownership, from 1968 to 1974, was in accordance with federal guidelines and that new, tougher laws cannot be applied retroactively.

The plant, said Ventron attorney Harry R. Hill Jr., was making a mercury-based fungicide and compounds for resale, obtaining the mercury from mines in Spain and Italy and from old battery casings and thermometers. At the time it was one of the largest such operations in the country, selling several hundred thousand pounds of the compounds each year. But three or four pounds of mercury per day were sloshing into the field and the stream when Ventron took over. Hill said Ventron managed to reduce that to about one-tenth of a pound per day by the fall of 1971, substantially complying with a goal set by the EPA.

"But they were hollering about mercury in effluent to the point where there was some feeling there would be none at all allowed in the future . . . and rather than get to that point, which would be uneconomical, we shut it down," Hill said. No mercury has been produced at the site since 1974, and the emission law now being cited passed in 1976.

Ventron disclaims responsibility and wants the state to go to the people who owned the site before 1968 or to the special Spill Compensation Fund of New Jersey to pay for the cleanup.

For eight years before 1968, the mercury compound plant was owned and run by the Wood-Ridge Chemical Corp., a wholly owned subsidiary of the Velsicol Chemical Corp. Velsicol is the Chicago-based firm involved in the Tennessee leakage case and in several other pollution controversies, and Velsicol also denies any responsibility.

"We did not conduct any mercury operations of any kind there," said Velsicol attorney John F. Neary. But didn't the conglomerate have total control of its subsidiary, Wood-Ridge Corp.? "We had the usual control of 100 percent stockholders, but no control of the day-to-day operations," Neary said.

"If we lose on this and get liability for ownership, anybody who owns property in New Jersey and finds out that 40 years ago someone put pollutants on their property . . . could be hit with a substantial judgment for something they didn't know about and had no part in," he said.

Velsicol also wants the state to use its Spill Compensation Fund to pay for any containment wall or other cleanup.

Attorneys for the fund argue in their turn that the fund was set up 1977, long after the Wood-Ridge plant closed down, and was intended anyway to finance mop-up operations for oil spills off the New Jersey coast. To use it at Wood-Ridge, they say, would be taxing the oil companies to pay for the chemical companies' sins.

The oil companies, unsurprisingly, support that view. "You just have to know New Jersey. There's no way to calculate the numbers of oil, chemical and liquid waste companies here . . . you could have thousands of this kind of claim," said Marvin J. Brauth, attorney for Exxon, Modil, Chevron and Texaco in this case. "If the state wants to clean this up it should pay for it out of a general revenue fund." "Nobody Fell Over"

SO THERE is the buck again, having gone round the circle and been passed back to the state. Going back further than Velsicol's subsidiary to the original site owners, F. W. Berk & Co., probably pointless since Berk is out of business. Velsicol still owns the polluted field of swamp grass behind Wolf's warehouses and maintains that, if anything, it is a victim there of others' waste.

Unraveling all this, Judge Lester is expected to make some kind of finding on the applicability of the pollution laws to events that occurred before they were passed. He will look at Velsicol's "corporate veil" and decide whether the firm is liable for what its subsidiary Wood-Ridge may have done. He will consider whether the state has obligations under its tidal waters responsibilities, and whether the spill fund is at all involved, and whether the various parties owe damages to one another. And then he will decide how the mercury is to be dealt with, trying to balance the degree of danger to public safety against the progressively higher costs of various remedies. The case is certain to be appealed.

While he ponders, Wolf's warehouse tenants try to ignore the problem. "We were upset when we found out about it, but we've had everybody in the world here to check the plant and there's no mercury anywhere," said Jerry Rosenblum, head of the J. Rosenblum & Sons Inc. food distributors warehouse.

"Well, we used to ask each other how we felt and all, and we were pretty upset at first," echoed Jill Thielmann, office manager of the neighboring Gailyn Packaging Crop. "But when nobody fell over in the first few days, well, you know how it is, you forget about it."