At a little-remarked of the House Merchant Marine and Fisheries Committee last month, a suave, conservative dressed man sat inconspiculously in the next to last row of the spectators' section, chain-smoking and following intently the progress of a bill to promote seabed mining.

When the session ended with the bill approved, he left as unobtrusively as he arrived.

Four days earlier the same man had been in London, buttonholing delegates to an international conference on the future of Antaretica and warning of Third World ambitious to co-opt the mineral resources of that vast southern continent.

In late May and early June he was in New York for the United Nations Conference on the Law of the Seas having lunch with the seabed mining committee chairman. In March he unsucessfully sought admission to another U.N. oceans conference in Geneva and in April he was briefing House committee staffers one day and testifying before a science and technology subcommitee another, both times as an expert on undersea minerals.

Wherever the future of ocean research and deep seabed mining is discussed, the ubiquitous man with neatly tailored prinstripe suits and French suits seems to show up.

His name is Leigh S. Ratiner, and he is the former chief U.S. negotiator on the seabed mining committee of the Law of the Seas Conference.

In January he resigned from the government and the next day took a job as lobbyist for the Kennecott Copper Corp., defending the company's plan to invest $700 million in harvesting enormous deposits of underwater nodules containing cobalt, nickel, copper and manganese.

Ratiner's odyssey through the cloak rooms of international diplomacy and the boardrooms of giant multinational corporations had placed him in the middle of a high-stakes global poker game.

It is a game in which the players are world power brokers, dividing up trillions of dollars worth of resources in the first attempt by mankind to apply principles of social order to the exploitation of the 70 per cent of the earth's surface covered by water.

For 10 years - largely out of view of an uninterested public - political and corporate leviathans have been engaged in a tug-of-war on the issue of deep ocean mining, trying to reach agreement on a treaty whose foundation is based on the principle that all resources under the sea are the common heritage of all mankind.

Developing nations, promoting a new world economic order on the one hand, and the industrial world, defending entrepreneurship and jealously guarding its technological store house, on the other have thrashed out one negotiating text after another, all the while failing to reach agreement on the key issues.

Now, admist charges that portions of a promising compromise text were secretly rewritten by a handful of Third World representatives - making them unacceptable to the United States and most other developed nations - the U.N. Law of the Seas Conference is in disarray.

Elliot L. Richardson, the chief U.S. negotiators, has said he is recommending to President Carter that the United States seriously consider with drawing from the treaty deliberations, which also cover pollution, scientific research, navigation and maritime issues.

Richardson objected that mining companies could be transfer technology to a seabed authority in return for mining rights, that the authority could control deep-sea scientific research and that the benefits of ocean mining could be made available to countries that did not accept the treaty.

In the words of one conference observer, the tiny state of Nauru, with a population of 7,000, would have about the same vote as developed nations committed to investments of up to $1 billion.

The House Merchant Marine and Fisheries Committee, frustrated by the on-again, off-again U.N. conference, approved an industry-supported bill that would allow mining companies unilaterally to begin harvesting the undersea mineral fields.

In language that unmistakably cast doubt on the world community's ability to reach any agreement , the House committee voted to guarantee industry investments against losses caused by any future treaty, and rejected an amendment to require the mining companies to pay 2 per cent of the value of their yield into an escrow fund that eventually would be distributed to lesser developed nations.

And in a development that may spell even worse news for the conference, prominent scientist involved in the negotiations have begun to express grave doubts about the treaty's future.

John A. Knauss, dean of the graduate school of oceanography of the University of Rhode Island, complained in Science Magazine. "I think, as complicated as life may be for scientists, we may be better off washing our hands of the whole thing." Knauss is the scientist closest to the negotiotions dealing with ocean science.

In their search to attach meaning to the failure of the sixth session of the Law of the Seas Conference - ended July 15 - delegates, advisers, technicians, staff members and other treaty advocates among the nations involved in negotiations since 1970 have privately begun raising troubling questions about whose best interests were served by the unraveling of the compromise text.

Richardson will say only that a "handful of people" rewrote proposals, making them fundamentally unacceptable to the United States, and the only name he mentioned was that of Paul Barnelo Engo of Cameroon, who headed the committee on seabed mining.

Several other names have cropped up, including those of the delegates from Sri Lanka, Trinidad and Jamaica, who are regarded in some quarters as Third World radicals who seek to dominate the distribution of the wealth of the oceans.

And because the unraveling of the U.N. conference and the predictable criticism by the United States seemed likely to have an immediate impact on Congress' deliberation on legislation sought by American mining companies, the name of the omnipresent Leigh S. Ratiner is also being raised with increasing frequency. With the raising of his name go unanswered questions:

What part, if any, did Ratiner's presence on the fringes of the conference play in Engo's surprise revision of the compromise text? Did he have access to information through Engo that encouraged the House committee to push forward with its investment guarantees legislation even before the conference? What conflict, if any, is there in Ratiner's sudden departure last Jan. 24 as chief U.S. seabed mining negotiator and his employment the next day by a Washington law firm that registered as a lobbyist for Kennecott Copper?

The questions have not been dampened any by the disclosure that in Appril Ratiner testified for three hours at a House seabed mining hearing without mentioning his position with Kennecott, and that the same month he briefed House staffers after being identified only as "Mr. Leigh Ratiner, former Committee One [seabed Mining] negotiator for the U.N. Law of the Seas conference."

The question have also not been muted by the fact Engo and Chris W. Pinto, the Sri Lanka delegate, have been described by Ratiner as close personal friends and confidants. A source close to Ratiner said the lobbyist routinely counseled Engo and Pinto when he was U.S. negotiator and afterward.

Richardson has not commented publicity about Ratiner's role on the periphery of the conference, but it was Richardson who personally barred Ratiner from attending the intersessional LOS meeting in Geneva in March, sources said.

Upon disclosure of the allegation that he used his contacts at the sea conference to supply the House committee, chaired by Rep. John M. Murphy (D-N.Y.), with inside information on progress of the treaty to spur it to act, Ratiner vigorously denied to a reporter last month that he had had any contact with the conference in the last two months.

However, very highly placed conference sources said they saw Ratiner at the United Nations immediately before and during the last session. The sources said that about May 13, Engo and Ratiner held a dinner meeting at a restaurant on First Avenue near the world organization, one of a series of contacts between the two before and during the LOS session.

Near the end of the session, they said. Ratiner met with Engo and other, unidentified, delegates in Atlantic City, N.J., for a "work session" at which the seabed mining treaty text was discussed extensively.

Engo, in a telephone interview from the Cameroon, initially denied having contact with Ratiner during and immediately preceding the New York session. When asked about the restaurant meeting, Engo recalled that Ratiner was in New York on a visit about that time and that they met in a restaurant.

"We weren't talking LOS business at all. We talked about his new job, completely. It had nothing to do with the [seabed] committee." Engo said.He denied vigorously that there were other meetings, and said he could not recall any telephone conversations with Ratiner.

Engo acknowledged Ratiner is a "close friend," and said, "Mr. Ratiner knows the system. When I feel two or three people can solve a probelm by getting together. I call on them in private conversations." But he said that was not done during the last session of LOS.

Ratiner was vacantioning out of town last week and did not respond to telephone messages left with his law firm. Dickstein, Shapiro & Morin. His secretary said he responded to one message by saying he was going camping and that inquiries should be made instead to Marne A. Dubs, director of the ocean resources department of Kennecott Copper Corp.

Dubs, in an interview in his New York office, said he knew about the dinner meeting and that Ratiner had told the leaders of the U.S. delegation about it beforehand to inquire if there was anything he could accomplish during the meeting.

Dubs said he knew of no other contacts between Ratiner and Engo, and that he "would be astonished" if there were any.

He denied emphatically the suggestion that Ratiner may have used his friendship with Engo either to funnel information to the congressional commitee, or to manipulate Engo in anyway.

"I think it's an unfounded proposal. The basis of the proposal seem to be that our company has invested in the failure of the Law of the Seas. That is a completely untrue and slanderous charge," Dubs said in a 2 1/2 hour-long interview.

He said Ratiner would have told him about any meetings with Engo or Pinto, and that he was confident that Ratiner's only involvement with LOS during the session was with the U.S. delegation.

"In my own opinion who tried to work out a scheme with Paul Engo would be mad. He's an unpredictable man," Dubs said.

Moreover, Dubs said his intrepretation of the compromise text is that it was nearly as unacceptable to the developed nations as the Engo text, and that he viewed Engo's revisions as "essentially minor changes."

Engo's motive, Dubs suggested, was that he felt co-opted in the last session and "wanted to put his own print on the text."

The stormy history of the Law of the Seas negotiations and Ratiner's role in them in both public and private life illustrates dramatically the magnitude of the wealth at stake.

At the initiative of the Maltese, world nations in 1976 began seriously considering how the enormous deposits of minerals on the seabed should be tapped under the auspices of an international control body.

In 1969, the U.N. General Assembly passed a resolution declaring all underwater resources the common heritage of mankind, and in December, 1976 - after a series of preparatory meetings - the first of six eight-week sessions began in New York.

The principal object of the Committee One deliberations - then and now - is how to govern the harvesting of potato-sized nodules lying on the seabed at depth of up to 15,000 feet. While nickel is the main target mineral, the nodules are known to contain copper, cobalt and manganese as well.

Scientists say there may be 1 1/2 trillion tons of nodules in concentrations of up to 100,000 tons per square mile, mostly in the Pacific Ocean between hawaii and Mexico. They are of high concentration, containing 1.5 per cent nickel, compared to the 7/10ths nickel taken from land mines.

Basically, four consortia of mining firms have been most active in developing seabed technology, investing $30 million to $50 million each in research and development and committing $100 million to exploration. The firms estimates they go to commercial operation by 1983-4 and say that investment decisions probably will be made in late 1979.

The harvesting system include a vacuum-cleaner-like device that sucks the nodules up to ore carriers, and a convey-like contumuous chain of buckets that reap the minerals.

(The consortia include such firms as Kennecott, Standard Oil of Indiana, U.S. Steel Corp., Lockheed Corp., Sun Oil Co., a U.S. subsidiary of International Nickel, Rio Tinto Zinc Corp., and Mitsubishi of Japan.)

Meeting in Geneva in 1975, the Law of the Seas Conference developed a single negotiating text which many developed nations, including the United States, viewed as most favorable to the Third World. It provided that only an international seabed authority would decide which sites would be mined, and that an international operating arm of the authority called "the Enterprise" would harvest the nodules for all mankind and control the distribution of profits.

In response, the United States the proposed a "Parallel" system under which there would be simulaneous mining by the Enterprise and the mining companies. A banking arrangement was proposed in which mining companies would identify two prospecting sites and the authority would reserve one site for The Enterprise and one for the private company.

The U.S. government substantially agreed to this concept, and then Secretary of State Henry A. Kissinger endorsed it, even though a thorny issue was an article which geared production limitations to the cumulative growth of the world nickel market.

However, major trouble revisited the fourth session of the conference in New York in May, 1976, when a rump group of delegations from six nations - known as the Brazil group - wrote a revised single negotiating text which was viewed by many delegations as a sellout to the industrialized nations.

Participating in that revision of the proposed treaty were Engo, as chairman of the seabed mining committee, and Ratiner, as chief U.S. negotiator.

In what was then viewed as the long-running conference's darkest hour, developing nations bitterly as sailed the text, saying they would get almost no benefits and complaining that no reasonable treaty could be possible with the involvement of the United States.

Ratiner and Engo were critized sharply for causing a breakdown in what might have evolved into a compromise, and the conference again fell into bickering and posturing among delegations.

It was against this backdrop that Jens Evensen, a cabinet minister of Norway and chairman of his country's delegation, agreed to a request by the conference leadership to mediate the seabed mining dispute and create a bridge between the industrial nations and the developing states.

Evensen, widely respected in the United Nations as an effective compromiser, in effect co-opted Engo's leadership of the seabed committee and in six weeks worked out a compromise text. Sources in the conference said that during this period, Engo virtually dropped out of sight, until the Evensen text was presented to him.

The hiatus for Engo, by all accounts, was out of character because of the Cameroon delegate's personality.

Imposing in size (6 feet-five) and striking in his bright blue floor-length dashikis, Engo is known around the United Nations as a gregarious envoy given to the cigars, John Wayne movies and good restaurants. In the 1964 Olympics he reportedly represented Cameroon in the hop, step and jump event.

In the mid-1960s, Engo served in Washington as charge d'affairs of Cameroon, a California-sized nation on the west coast of Africa between Nigeria and Gabon.

Law of the Seas Conference sources said Engo took the Evensen compromise text to this Manhattan East Side apartment and worked on it privately, without consulting the U.N. secretariat, the conference staff, or industrial nations' delegations.

"The revisions were literally done outside the building, which is not surprising when you remember that Paul Engo works very close to the hip. He does things on the basis of friendships." said one conference source.

Sources in the conference recalled that when the handwritten revisions were returned to U.N. Under Secretary General Bernardo Zuleto, Secretary General Kurt Waldheim's special representative to the conference, Zuleto said he was worried about the possible repercussions and tried unsuccessfully to get Engo to change his mind.

Other attempts were made as the July 15 dealine for adjourning the session neared, but the revisions were released the next week substantially as Engo had made them.

Now, say conference officials, it will be up to the seventh Law of the Sea conference session scheduled in March in Geneva to salvage something out of the disarray resulting from the Engo text.

A side-by-side comparison of the Engo text and a confident "framework of position" document prepared by the developing nations appears to call into the question the thesis that the Third World was responsible for stimulating Engo to rewrite the Evensen text.

Engo's draft contains stiff pro-Third World clauses in many of the articles that are not contained in the position paper prepared by the Group of the bargaining collective of developing nations.

For example, the extent of the seabed authority's control over mining operations, and provisions for forcing transfer of technology, appears to be much broader in Engo's text than in the Group of 77's framework document, a copy which was obtained by The Washington Post.

Conference sources asserted that the comparison puts the lie to the widely held view that the developing nations' inflexibility led to the Engo text and the subsequent unraveling to the negotiations.

Dubs challenged that assertion, arguing that while some of Engo's measures may not have been put in writing by the Group of 77, the consensus of the group favored them during close deliberations.

Engo critized Richardson for "creating distortions" about how the transfer-of-technology revisions were made, and angrily denounced "those who have impugned my whole integrity" by suggesting he was influenced by anyone.

"I went through all these things and took the decisions myself," Engo said while acknowledging he counseled, "experts," including Pinto and Kenneth Rattray, alternate chairman of the Jamaican delegation, among others.

Whether seabed mining committee delegates will use the Engo revision as a bargaining stick to further their own interests remains to be seen, although there have been signals from some nations in the developing nations bloc-known as the Group of 77-that they are upset over what Engo produced.

"It is now well understood what happened and everyone recognizes in (the text) for what it is," a source close to the conference said. He then added, "But the U.S. delegation maybe particularly sensitive to the fact that one of their former delegate may have had something to do with screwing things up for a while."