By itself, the process is simple enough.

The House passes a bill, the Senate passes a different but similar bill. But before the bill can become law, the differences must be resolved.

Each chamber selects a delegation, usually members of the committees that worked on the bills, to iron out the differences. Technically, they hold a conference, and those who do the conferring become conferees.

That is the theory. In practice, House-Senate conferences diverge from the textbook and become something far different.

In their rawest form, they are brawling, ego-driven tests of will; wrenching clashes of philosophy, muscle and politics.

It is a process that gives us a phenominon of this and practically every December, or every period in which the Congress is rushing to a recess - governance by the few in the arena of the conference.

It is a process that gives us a Labor-HEW appropriations measure stymied for four months over abortion language. A process that stymies crucial energy and Social Security bills, with time becoming a tyrant.

And it is a process controlled almost without exception by the marathon runners of Capitol Hill, stalwarts who know the road map of negotiation by heart in the dark and use the pressure cooker of a running clock with adroitness.

"It is a game played by some," commented Sen. Henry M. Jackson (D-Wash.), chairman of the Energy and Natural Resources Committee, a member of Congress since 1941.

"When we get near adjournment, two or three months away, they try to start delaying, try to avoid early consideration, knowing you can block a bill . . . it is all a procedural part of the system," he said.

Jackson did not say so, but he could have been referring, for example, to Sen. Russell B. Long (D-La.), a man who plays the keyboard as though he were at a cathedral organ.

This year, as in recent years past, the imposing footprints of Russell Long are all over major bills snagged in the trap of time that ensnarls a Congress lusting to recess.

Today, vital Social Security and energy bills. Yesterday, a delayed black-lung benefits bill for disabled coal miners. Next year, tax reform and welfare. As chairman of the Finance Committee, dealing with these issues, he becomes pivotal.

He becomes a man as powerful as any other in the country - and perhaps more so - by virtue of his rank, his acumen and the deference that comes with being a chairman and a stalwart.

Yet on this backdrop of power politics, another factor intrudes. Call it whim. Call it caprice. Call it the human factor.

A vignette:

Two weeks ago Sen. Long's wife Carolyn, was celebrating her birthday. He wanted to get home early but there he was at dinner time, sitting with other conferees in a chandeliered meeting room, arguing about black lung.

They were deadlocked then, just as they had been for weeks. Long warned that he intended to celebrate and in so saying, he sent a signal.

The signal - meaning the time had come to compromise - resulted in a major public policy decision affecting thousands of lives and costing consumers and corporations millions of dollars.

The conference chairman, Rep. Carl D. Perkins (D-Ky.), caught the signal. He suggested that the conferees step out into the hallway and strike a deal.

They did precisely that and within minutes returned to the room with an agreement that worked out a formula for financing the black-lung benefits program.

Russell Long didn't get what he wanted. Carl Perkins didn't get what he wanted. But they were guided by the key to the equation: precious time.

Why do major bills get clogged in the pipeline only to surface when the pressure of recess or adjournment has built to levels that impede - or actually inspire - rational thinking?

Henry Jackson has one answer. Another is provided by a long-time congressional staff assistant:

"Part of it is that human factor - procrastination. The time for review, though, is less. When it's just between a man and his job, delay is manageable. But when it involves a group, the quality of decisions diminishes."

The language was different, but the Commission on the Operation of the Senate said essentially the same thing last year in its final report.

"The legislative process as it presently operates appears to be organized primarily for incremental decision-making rather than addressing major problems in a comprehensive manner . . . At some early point advocacy tends to take over from objective inquiry," the report said.

In this era of reform, conferences are now open to the public - unless the conferees vote otherwise. In the recent past, conferees met privately, cut their deals and presented their colleagues and the public with take-it-or-leave-it legislation. Even with reform, it is worth noting that transcripts still are not made of most conference meetings.

One result of the open conference, as Jackson and others see it, is that the entire process is slowed.

"There is posturing, with the television there, with the press and the public here," Jackson said. "The public process is important, and I support it, but you pay a price.

"In order to do the job, we have to have private conversations. Either we are whispering or we go out and have coffee. The real decisions come in private.

As he talked, Jackson was on his way to a private caucus of Senate conferees who were trying last week to find some way to break a seemingly unbreakable deadlock on the natural-gas portion of the energy bill.

That same day, the Social Security conferees were locked into an equally tortuous snarl, which opened the way for the sort of wheeler-dealer movement that Jackson talked about.

Sen. Long and Rep. Al Ullman (D-Ore.), chairman of the House Ways and Means Committee, sat down in private with their staffs and worked out what they thought was a solid compromise, each side giving a bit.

The deal wobbled after House Democrats objected to their chairman's attempt to break the impasse.

Another of the energy conferees, Sen. Wendell H. Ford (D-Ky.), who has been targeted as a man who might shift and break the deadlock, sees "more pluses than minuses" in the system.

"The pressure is there, certainly," he said, "but it is not that bad. When we put everything else aside and concentrate on energy, as we are doing now, you led your intellect to that particular item that is being discussed . . .

"When everything else is set aside, you think, you chat, you have lunch and talk about the issue all the time . . . In these private talks, we stay away from the bottom line, we look for soft spots, what we can accept, what we can offer them."

Energy, Social Security and the fight over abortion are the headline-grabbing issues, but the conference procedure is occurring almost constantly on Capitol Hill.

Many of the disputes between House and Senate are resolved quickly and amicably. But many others go on just as tangled as energy and Social Security, involving similar wills and egos, although their national implications are not as great.

A near-classic example is the deadlock in which a committee of Interior conferees finds itself on a bill that would protect more than 1 million acres of endangered wilderness land from the incursions of developers.

It is an issue that involves jobs and local economies, the integrity of the national forest system and, inescapably, politics . . .

The House version of the Endangered American Wilderness Act would add 1.1 million acres to the preservation list in nine states. The Senate would add 1.2 million acres in eight states.

Through a series of conference sessions, compromises were struck on all but one of the disputed land packages - proposed additions to the Siskiyou National Forest in Oregon.

Rep. Morris K. Udall (D-Ariz.) and Sen. Frank Church (D-Idaho), leaders of the conferees, see the disagreement as one that must be resolved soon to avoid entangling the legislators in election-year squabbles at home over the volatile land-preservation issue.

It so happens tht the two protagogists of the fight - Sen. Mark O. Hatfield (R-Ore.) and Rep. Jim Weaver (D-Ore.) - will be up for re-election in 1978. They are in bitter disagreement over the amount of Oregon land to be taken.

In Oregon, their dispute has been the subject of wide-spread news coverage and editorials. Timber companies have published ads decrying Weaver's proposal to protect some 280,000 acres, while approving of Hatfield's 82,400-acre take.

The dispute has taken on a jobs vs. preservation air. Mining and lumber companies want access to the resources that otherwise would be put into cold storage by the House version.

In the spirit of compromise the conference system is intended to promote. Hatfield has moved to accept 92,000 acres and Weaver has set 134,000 acres as his bottom line.

But there they are stymied and neither man is showing the slightest sign of yielding further. And because of complexities of House rules, the issue cannot be dropped. There will be a final bill - with the Oregon acreage - or no bill at all.

Such is the system. Such is the process.