Nelson Bunker Hunt and W. Herbert Hunt are scheduled to testify before two congressional committees today to add their version of what happened in the silver market to the picture that has emerged from three days of hearings this week.

Late yesterday attorneys for the Hunts said the billionaire brothers will answer a subpoena from a House government operations subcommittee that has threatened the Hunts with jail if they don't appear.

The brothers agreed to meet with the House panel, chaired by Rep. Benjamin Rosenthal (D-N.Y.) in the morning, before their afternoon appearance at a Senate subcommittee headed by Sen. Donald Stewart (D-Ala.).

The brothers failed to show up at Rosenthal's hearing on Tuesday and the subcommittee voted to cite them for contempt of Congress, a charge that could lead to a jail term.

Yesterday Steward's Senate subcommittee made public a Commondity Futures Trading Commissioni report that gives the most detailed explanation yet of the Hunt's silver-speculating spree. Stewart's hearings produced these disclosures:

A group of banks and metal dealers were preparing last month to step into the silver market and buy more than $1 billion worth of metal to keep prices from falling further. The bail-out method was called off after silver prices bottomed out at $10.80 on March 27 and began to go up again.

Ten major banks loaned $233 million to a subsidiary of Bache Group Inc. and took 17 million ounces of silver as collateral. The banks sold 10 million ounces of the silver on March 28 and paid off $125 million of the debt.

Two large privately owned commodity firms, ACLI International and Conticommodity Services, suffered such heavy silver trading losses that their owners were forced to come up with $138 million in new capital to keep them solvent. ACLI is controlled by Aldrain C. Israel, chairman of People's Drug Stores of Washington.

Foreign traders, dealing through ACLI, Conti and a Swiss bank, followed the Hunts down the silver path and bought tons of the metal, contributing to the crisis in the silver market.

Steward queried Federal Reserve Board Chairman Paul A. Voicker and several other witnesses yesterday but failed to get an answer to the most difficult question raised in the three days of hearings:

Why are the Hunts arranging a $1 billion loan from a group of banks when most of their known silver-speculating debts already have been paid?

The loan has become one of the central issues in the hearings, because it is being negotiated with the knowledge and consent of Voicker, who has been telling banks for months not to make loans for speculative purposes.

Volcker testified yesterday that special provisions of the loan agreement will require the Hunts to dispsose of much of their silver hoard "in an orderly fashion."

Calling it "a damage control loan," Volcker said the huge borrowing will let the Hunts pay off debts to brokerage houses. CFTC officials, however, said the Hunts' futures-speculating debts never exceeded $125 million and virtually all of that amount has been paid.

Stewart and other committee members repeatedly criticized the billion dollar bailout, pointing out that farmers, homebuilders and small businesses are in financial trouble because they cannot get loans.

Sen. John Melcher (D-Mont.) asked Volcker and other witnesses whether the Hunts and their fellow silver speculators violated federal antitrust laws by artifically inflating silver prices.

Volcker and Treasury Department officials said they had not raised the issue. CFTC Chairman James Stone, on the advice of his agency's chief counsel, refused to say whether commodity regulators have talked with the Justice Department about possible antitrust violations. Melcher said he took that to mean the answer was yes.

Plans by a group of investment bankers and metals dealers to step into the market were revealed by Dr. Henry Jarecki, chairman of Mocatta Metals Corp., the New York affiliate of a London firm that is one of the world's biggest gold and silver dealers.

In prepared testimony, Jarecki said the group members "were prepared to prevent any serious economic dislocations from occurring" from the collapse of silver prices.

"We had notified the exchanges . . . and the brokerage houses involved that is a massive selling wave hit, we would need ti know only the exact number of ounces that had to be taken up to prevent further panic selling," he said.

The Jarecki group was prepared to pour more than $1 billion into the silver market in hopes not only of preventing prices from falling further, but also of making quick profits of hundreds of millions when prices rebounded. The plan was called off after silver climibed from $10.80 on March 27 to $13 the next day.

THE CFTC report showed that daily losses "in excess of $10 million had become commonplace" for the Hunts, when silver prices were falling.

According to the CFTC, the Hunts at the end of December owned 90.3 million ounces of silver -- worth more than $3 billion at that time -- and another 28.6 million ounces were in the hands of foreign traders dealing with ContiCommodities.

The Hunts and the foreign group also held more than 17,700 silver futures contracts, allowing them to buy another 88 million ounces.

Stone said the CFTC is taking legal action against the Swiss bank through which many foreign investors speculated in silver because the bank has refused to name its clients.