In the fifth week of the Constitutional Convention of 1787, James Madison related to the delegates an ominous vision of America's "future danger."

The population will increase dramatically, he predicted. As it does, so will the proportion of people who are poor, who "labor under all the hardships of life." They will "secretly sigh for a more equal distribution" of the country's blessings, he hinted darkly, and before long, there will be more of them than of us. Power will "slide" into their hands.

To guard against this bleak future, to ward off the "leveling spirit" that was rearing its head across the land, Madison advocated the creation of a special elite branch of government -- small, stable, upper crust and "respectable for its wisdom and virtue."

Thus was born the Senate of the United States, two centuries ago this week, in an interlude during the convention between more fiery battles over power. By the end of the week, the delegates had laid the foundation for the Senate, for the terms of office of its members, its mode of election and its independence.

While some of what the delegates did remains intact today, pound for pound, the institution has changed perhaps more than any of the others they created. At 100 members, the Senate is not nearly as small as they had hoped. Now elected by the people, rather than the state legislatures, it no longer speaks for the governments of the states. One of the few surviving features is one designed to make the Senate wiser: the age limitation requiring senators to be at least 30 years old versus 25 for members of the House.

Ironically, the characteristics of the Senate today that probably would have pleased the delegates the most are the ones that so enrage modern critics of the Senate. Most of the delegates to the convention wanted the Senate to "meddle" in foreign policy. Many would have been happy to hear that it protected business interests. It was intended, as George Mason of Virginia said, "to secure the rights of property," or, in Alexander Hamilton's words, to protect "the few" from "the many."

Finally, the number of rich men in the Senate (at least one-quarter are millionaires, according to financial disclosure reports) would have made many of the framers ecstatic. Many of them, like Charles Cotesworth Pinckney of South Carolina, would have wished that there were more. Pinckney proposed that no salary be paid to senators. "This branch," he said, is "meant to represent the wealthy of the country." If no salary is paid, "the wealthy alone would undertake the service."

His proposal lost by the vote of a single delegation.

Their idea of a Senate was to some extent a remnant of days gone by. Once, in Britain, the divisions of government had reflected the divisions of society, with the upper house -- the House of Lords -- seen as the guardian of the landed nobility. There were no dukes, earls or lords in the United States in the 1780s, but there was a kind of aristocracy -- an aristocracy of the respectable. The delegates knew about this aristocracy because they were it.

In fact, when they got down to the serious business of constructing a Senate -- following the defeat of the New Jersey Plan of government on June 19, 1787 -- Benjamin Franklin cautioned his colleagues to restrain themselves when deciding on the pay for senators. "There were a number of young men" in the convention who would undoubtedly serve in the upper house, he said, and if the pay was too high, "we might be chargeable with having carved out places for ourselves."

Having three weeks earlier strained every fiber to convince fellow delegates of the need for a popularly elected House, Madison did not have to work hard to convince the delegates of the need for his Senate. A popularly elected House, as the states had proven, was intrinsically dangerous. If there had to be one, there had better, by God, be a Senate to watch over it.

The "democratic licentiousness of the state legislatures proved the necessity of a firm Senate," declared Edmund Randolph of Virginia. The very thought of not having one, agreed Elbridge Gerry of Massachusetts, ranked among "the wildest ideas of government in the world."

The insurrection of farmers in Massachusetts, the rise of popular parties in state after state and the increasing alarm of the propertied classes about the "leveling spirit" had only heightened the need.

Only Franklin argued seriously for a one-house legislative branch, a pet idea of his, and he knew he was going against the tide.

If there was a model, it was the Senate of Maryland, admired by many of the delegates because of its manly stand against the issuance of paper money to help debtors save their farms. Maryland's Senate had 15 men, each with five-year terms, each required to possess at least 1,000 pounds in property. The members were chosen by an electoral college composed only of the propertied.

And the great task for the convention in creating the Senate was limiting admissions: making it small, wise and stable, keeping the wrong people out, letting the right people in.

The concern about stability and continuity stemmed from the notion that the Senate would carry great responsibility for the conduct of government, especially for foreign policy. "The true reason" that Britain was refusing to discuss a commercial treaty with the United States, said James Wilson of Pennsylvania, was that "she had no confidence in the stability or efficacy of our government."

The Senate, he said, "will probably be the depository" of foreign policy powers. "It ought therefore to be made respectable in the eyes of foreign nations."

Senators, Madison said, should have time to acquire "a competent knowledge of the public interests."

From the outset, thus, the convention envisioned a longer term of office for senators than for members of the House, who had been given two-year terms. The question about senators was how long.

Robert Morris of Pennsylvania, George Read of Delaware and, of course, Hamilton -- who confessed that he really wanted an American House of Lords -- advocated life terms for the senators. The proposal found no additional support in the convention. "It would never be adopted by the people," Gerry of Massachusetts said.

Nine years was then proposed, but many found that excessive as well. "If the senators should be appointed for a long term," said Pinckney of South Carolina, "they would settle" in the nation's capital and "would in a little time be rather the representatives of that than of the state appointing them."

Others, while seeing a necessity for longer terms, still thought that frequent elections were necessary, as Roger Sherman said, "to preserve the good behavior of the rulers." Sherman and others favored four-year terms.

The convention was searching for a middle ground when Wilson threw another factor into the equation, which he hoped would make a long term more acceptable. One of the main objections to long terms, he suggested, was that when election time came, and all the senators realized they faced possible ouster from office, they might try to "prolong" their tenure, even converting themselves into a "hereditary" body.

To avoid this, he proposed staggering the elections, so that only a third of the senators would face reelection at one time. The convention accepted the idea. This meant, however, that the tenure had to be divisible by three.

The number nine being too great, four being too little, five being mathematically inconvenient, they were left with six. Six-year terms for members of the Senate.

Who would elect the senators? Two strong currents favored appointment of the senators by state legislatures. First, it would give the states their only real role in the new government. Without it, in the plan then under consideration by the convention, they would be stripped of any direct say.

Second, few in the room trusted the people to make the choice for such an august institution. "The commercial and monied interest would be more secure in the hands of the state legislatures than the people," Gerry said. "The former have more sense of character and will be restrained by that from injustice."

The convention delegates themselves had been chosen primarily by state legislatures, said John Rutledge of South Carolina, the ultimate proof of good taste. "If this convention had been chosen by the people," he said, does anyone think that "such proper characters" would have been selected?

Thus, they decided on June 25 that the state legislatures would elect members of the Senate, a decision that was undone on April 8, 1913, by ratification of the 17th Amendment to the Constitution.

What to pay senators, as well as of representatives, was a source of considerable debate in the convention. The states paid the expenses of members of the existing Congress under the Articles of Confederation. When the states ran out of money or disliked the conduct of a member of Congress, they would simply starve him out by cutting off the flow of money. In this way, they exercised even more control over the Congress than they already had by virtue of choosing the delegates.

Madison and others felt that to continue this practice, as Johnathan Dayton of New Jersey put it, "would be fatal" to the independence of Congress.

They had a small fight on their hands from states' rights advocates, however, but Madison rose to it. "One great end of the institution {the Senate} was that being a firm, wise and impartial body, it might not only give stability to the general government in its operations on individuals, but hold an even balance among different states." Letting the states control salaries, he said, "would make the Senate like Congress, the mere agents and advocates of state interests and views, instead of being the impartial umpires and guardians of justice and general good."

Madison won this crucial issue on June 26 -- by one vote.

Perhaps the greatest dilemma was controlling the size of the Senate. All agreed it should be small, for large bodies are subject to "passionate proceedings," as Randolph had said. But in the previous week -- amidst a great battle between the large states and the small -- the convention had voted to make representation in the Senate proportional. Each state would be represented according to the size of its population.

It was beginning to dawn on some of the delegates already that a Senate based on proportional representation could not be small. According to their estimates of state populations, if the smallest state had one member in the Senate, the largest would have up to 16 or 17. Taking all the states into account, including those expected to come into the union soon, that would put as many as 80 or 90 people in the Senate, one delegate estimated.

And that was much too large.

The delegates had finished their informal work -- in the "committee of the whole." Now they would go over everything again, this time far more seriously.

As the delegates contemplated their conundrum, they thus moved once again into a reconsideration of representation in the Senate, preparing for another donnybrook.NEXT MONDAY: Deadlock