By 3:45 p.m. it was standing room only in the galleries, and colleagues from the House had taken their places along the back wall of the Senate chamber. History in action.

Majority Leader Robert C. Byrd of West Virginia was on his feet, rising to the occasion. He invoked that midnight conversation between Brutus and Cassius before the battle of Phillipi. Then, in the language of Shakespeare, Byrd sounded the final call:

"There is a tide in the affairs of men which, taken at the flood, leads on to fortune."

The Senate, he said, had reached such a tide: "The Rubicon of decision on the treaties is now to be crossed."

It all had the ring of high drama - the crowded chamber, the critical vote on the first of two Panama treaties, the glowering skies, the sleet and snow, Big portents.

In fact, the debate itself was listless, tepid and robbed of suspense.

The senators were playing out their public scene, but the outcome already had long been locked up in private.

As Robert Dole of Kansas, who stood against ratification to the end, told collegues in sardonic tones:

"We're down to the last 25 minutes. I'm not sure what's happening in the back rooms, but the votes are there . . . The American people lost."

That, of course, was the view of the losing side. For Jimmy Carter and his administration, the first hurdle in gaining their first big victory had been passed.

After 22 days of deliberations, the longest over any treaty since the fateful debate over America's joining the League of Nations after World War I, the Senate finally had spoken.

It was close - a one-vote margin - but sure. Other votes were there if needed.

The last hour of debate before the final tally permitted the record to be filled with the kinds of statements politicians love.

Senators, as is their wont, praised themselves and their system in stilted language. "I believe we've negotiated our way through the rocks and shoals of debate," the minority leader, Howard Baker, told his colleagues.

Then, the pat on the back:

"In a word, Mr. President, the Senate of the United States has comported itself well."

Baker, who led 15 other Republicans in voting with the majority for ratification, gave the political rationale for joining the Democrats. The American people favored the treaties, he said, citing a public opinion poll he had commissioned in his own state of Tennessee. Besides, he added, a vote for the treaty demonstrated that he had the other GOP members were not clinging to the status quo.

The opponents were equally assertive, but measured in their remarks.

To Robert Griffin of Michigan, the Republican veteran, "This instrument called a treaty is a mask of ambiguities." To Malcolm Wallop of Wyoming, a GOP freshman, the treaty recalled the story of the emperor's new clothes: people pretend he's dressed for the ball when "our little emperor is as naked as he can be."

What's left of the southern Old Guard added their voices, but the sound was a thin echo of their old power.

Strom Thurmond of South Carolina, the Democrat-turned-Dixiecraft-turned Republican apostle for the southern strategy, stood in the aisles flailing his arms and bemoaning what was happening. The Panama Canal treaties were, he said, "the dead giveaways of the century."

John Stennis of Mississippi rose in the back of the chamber to worry about the cost. Billions, he said, may have to be paid by us in the end. That, and something else - "the overwhelming point here is that we are moving out, leaving the sidewalks swept clean . . ." He added, in a sigh for the past:

"We're giving up a lot."

Nor was rhetoric absent from the closing scene. Big Jim Allen of Alabama had only 2 1/2 minutes in which to praise his side, those who stood against ratification. He saw in the actions of that vanquished band political bravery akin to that recorded in John F. Kennedy's book, "Profiles in Courage."

The victors were not averse to a bit of drum-beating, either. Frank Church of Idaho likened the moment to 200 years ago throwing out the hated red-coats. Said Church, in martial accents, it would be "back to the trenches" if the treaty failed.

But it was Byrd, the Leader, who reached back the farthest to wring out the most drama. He began with Caesar - and ended with him. In between he lectured the Senate on how thoroughly the subject of the treaty had been explored. None as much during his 20 years of Senate service, he said.

Then, in his peroration, he returned to Caesar: "Caesar once asked a question of his captain: 'Will the day be fortunate for us?'," the senator recited.

You've probably guessed the answer, but just in case it had the centurion saying to Caesar: "You will be victorious."

And, indeed, that's how it came out. Jimmy Carter may not be Caesar, and our Senate doesn't exactly resemble glorious ancient Rome, but they won one on the day immediately after the Ides of March, and a big one at that.