Last year, Sen. Russell B. Long (D-La.), longtime chairman of the tax-writing Senate Finance Committee and now its ranking minority member, supplemented his $60,663 salary with $625,000 from oil and gas royalties, according to his financial disclosure statement filed with the secretary of the Senate.

While attention has been directed at honorariums received by senators, a survey of the financial disclosure statements shows that many receive substantially larger amounts from a variety of other sources.

Thus, the Senate remains in essence "a rich man's club," with some members born to wealth, others having earned it before coming to Washington, and a few seeking to make it here.

During 1981, for example, John Glenn (D-Ohio) collected some $525,000 from his motel holdings in Florida, put together before he ran for public office. Charles H. Percy (R-Ill.), chairman of the Foreign Relations Committee, sold $185,000 worth of oil stocks.

Ernest F. Hollings (D-S.C.), ranking Democrat on the Budget Committee, opened up a $250,000 margin account with the New York brokerage firm of Donaldson, Lufkin & Jenrette.

Mark O. Hatfield (R-Ore.) sold a Washington apartment building worth more than $100,000 and received rents from other properties totaling more than $20,000.

Wendell H. Ford (D-Ky.) took in $147,000 from his insurance company partnerships. Bill Bradley (D-N.J.) reported he collected $95,700 as deferred compensation from his days as a basketball player with the New York Knickerbockers. And Lawton Chiles (D-Fla.) received $198,581 from his partnership group that owns four Red Lobster inns in Florida.

Then there are the senators with inherited money. John Heinz (R-Pa.) has income from two trusts and his H.J. Heinz dividends, each giving him an income of more than $100,000. John C. Danforth (R-Mo.) has three trust incomes of more than $100,000.

Claiborne Pell (D-R.I.), with his wife, showed income from a half-dozen trusts totaling well over $400,000. And Edward M. Kennedy (D-Mass.) has two trusts bringing in more than $100,000 and three others drawing from $50,000 to $100,000.

Several senators reported oil property holdings and income. J. Bennett Johnston (D-La.), second-ranking minority member on the Energy and Natural Resources Committee, reported $21,000 from oil leases in Louisiana and Texas and the purchase and sale last year of additional acreage valued at between $100,000 and $250,000.

Nancy Landon Kassebaum (R-Kan.) reported oil and gas royalties and distributions of more than $2,000 last year. Quentin N. Burdick (D-N.D.) declared more than $5,000 in income from "oil leases."

The wife of Majority Leader Howard H. Baker Jr. (R-Tenn.), daughter of the late Everett McK. Dirksen (R-Ill.), is listed on Baker's statement as receiving royalties "in excess of $1,000" last year from each of eight different oil companies including Gulf and Mobil.

Long not only collects large amounts for rents and royalties on properties he has had for years, but, according to his latest report, he made additional purchases of oil land last year.

John G. Tower (R-Tex.), chairman of the Armed Services Committee, reported he received $15,000 or more in 1981 from the lease of "drilling rig equipment." In the same filing he reported the purchase of "drilling rig equipment" valued at $107,039 and the borrowing of $108,000 from the Mercantile Bank of San Antonio; the "lease agreement on drilling rig equipment" served as collateral.

Tower said his interest rate on the loan is 1 percentage point over the federal discount rate, which was 15 percent initially.

Howard W. Cannon (D-Nev.), a colleague of Tower's on the Armed Services Committee, appeared to get a somewhat better deal on interest on more than $40,000 in "personal loans" he made last year from the First Western Savings Association of Las Vegas. That bank, according to Cannon's report, charged him only 9 percent on five separate loans last year, at a time when the general public was paying almost twice that amount.

That 9 percent may be the going figure in Nevada, at least for senators. Paul Laxalt (R-Nev.) reported he was being charged that amount on a small, personal loan he had outstanding from the Nevada State Bank in Las Vegas.

One explanation for Cannon's borrowing may be a liability listed in his report: an "estimated additional 1981 tax liability" put at between $50,000 and $100,000.

Majority Whip Ted Stevens (R-Alaska) reported ownership of $50,000 or more in a Dallas-based limited partnership called 4th Rig Associates, along with two Oklahoma City-based oil and gas leasing operations, PCX Corp., with a value of $15,000 or more, and Fain-Porter Production Co., worth $100,000 or more.

Stevens also reported several major purchases in 1981: in January, a carriage house on Capitol Hill valued at $50,000 to $100,000; in April, a boat valued at more than $15,000 at the Capitol Yacht Club; in June, stock valued at at least $15,000 in City Deposit Corp. of Anchorage; in September, at least $15,000 for a partnership in Capitol Exploration Co. of Washington, D.C.; in October, the Tres Alamos Ranch in Yavapai County, Ariz., valued at more than $250,000.

Two senators reported significant income from the news media. Barry Goldwater (R-Ariz.) disclosed he collected $14,375 from Cable News Network for commentaries. And Robert J. Dole (R-Kan.) reported $18,000 from a Los Angeles outfit that syndicates the five short radio commentaries he turns out each week.

Several senators are active stock or commodity traders. Percy reported over 30 transactions during the year, 15 of them involving the purchase or sale of securities valued at $50,000 or more. Alfonse M. D'Amato (R-N.Y.), on three separate days bought and sold the same stock, each time valued at $30,000.

Steve Symms (R-Idaho) traded in commodities, including silver, during the year and Gordon J. Humphrey (R-N.H.) actively traded in 43 different stocks and reported a capital gains income of more than $100,000 from 24 of them.

For nearly half the members of the Senate, however, honorariums represent the major additional source of income outside their salaries. Often, members with the largest outside incomes pass up taking honorariums, a survey of the reports shows. Long and Glenn, for example, took none during 1981, although they both made numerous speaking appearances before organizations that pay fees to their colleagues.

Glenn, in an interview, put it bluntly: "We're making enough money so that I could stay away from honorariums. I declined them, because of the trouble they cause, and just let the sponsors pay my expenses."

Long also did not take any speaking fees during the year, although he did permit the Mid-Continent Oil and Gas Association to pay two days of food and lodging for him and his wife at their New Orleans convention, where he gave a speech. CAPTION: Picture 1, SEN. JOHN GLENN . . . $525,000 from motel holding; Picture 2, SEN. RUSSELL B. LONG . . . $625,000 from oil and gas royalties; Picture 3, SEN. CLAIBORNE PELL . . . $400,000 from half-dozen trusts; Picture 4, SEN. MARK O. HATFIELD . . . sold building worth over $100,000.