July 26, 1981

Kathy Whitworth, the 41-year-old Texan who has 81 professional golf victories but not a single United States Open championship, took sole possession of first place in the third round of the 36th annual Women's Open championship today at six-under-par 210. Tied for the lead with Beth Daniel after the first round and tied with Bonnie Lauer after the second, Miss Whitworth shot a 71 at the La Grange Country Club to take a one-stroke advantage over Miss Lauer, who shot a 72. Miss Whitworth moved to an early three-shot lead over Miss Lauer.But when Miss Lauer holed out a 20-foot bunker shot for a birdie 3 at the 15th hole and Miss Whitworth took three putts for a bogey, the lead was trimmed by two shots. They remained a stroke apart through the last three holes as each of the leaders finished with a birdie 4 at the 18th hole.

ARMONK ANEW local law regulating burglar and fire alarms in the town of North Castle - a northern Westchester municipality with many reasonably affluent communities - is causing some alarms of its own among residents. The law, which officially took effect on July l, is aimed at protecting police services against the increasing problem of false alarms. The new law requires homeowners and businesses to apply for $15 permits for their systems and to pay a $10 fine for each false alarm. It empowers the town's Chief of Police to revoke the permit if more than five false alarms are transmitted in any one year. Officials said the new law was patterned after one in White Plains.

13HUNTINGTON ITS incredible sunsets, isolation and raw beauty make Hobart Beach, commonly called ''Sand City,'' the most magnificent town beach in Huntington, and possibly the Island, according to people who frequent it. A peninsula that juts out into Long Island Sound from Eatons Neck, it is washed on one side by the waves that come rolling in from the open waters of Long Island Sound. On the other side, it is gently bathed by the calm waters of Northport Harbor and Huntington Bay. A drop in the water level on the bay side creates ideal swimming conditions - almost like a pool, said Jill Thonger of Eatons Neck, who has been coming to the beach for 21 years. And the unusual land contours in a cove called Prices Bend provide shelter for about 35 vessels, mostly sailboats.

In the last few months, demand for land has been rising rapidly along with prices here on the North Fork, one of the twin prongs splitting off from Long Island's wide midsection. With the escalation has come concern that the North Fork may be colonized by new summer residents who cannot afford the prices on the other prong - the South Fork, which encompasses the Hamptons and Montauk - but will attract the kinds of restaurants and discotheques that appeal to the crowd that summers there. From the flat fields of Cutchogue to the area's traditional commercial center in Southold to the beach at Orient, people on the North Fork worry that such an influx would intrude on their way of life. ''The general feeling about someone who wants to tell the world about the North Fork is, don't tell 'em,'' said John Nickels, a town councilman and real estate broker. ''We don't want to spoil it here.''

English critics regularly cite Albert Finney as one of the great actors of his generation, but American audiences have not had many opportunities to judge for themselves. We may have read about his stage triumphs in London, but only a couple of them have ever made it across the Atlantic. And his movie roles have been few and far between. In the 20 years since his electrifying debut in ''Saturday Night and Sunday Morning,'' he has made only a handful of films, including ''Tom Jones,'' ''Two for the Road,'' ''Scrooge'' and ''Gumshoe.'' His last screen appearance was in ''Murder on the Orient Express,'' almost seven years ago.

WORRIED about the possiblity that Suffolk County this year will again lead New York State in the number of auto-accident fatalities, police and safety officials in the county are stepping up their efforts to make local roads safe for drivers, passengers and pedestrians. Nassau officials, concerned with their county's rate, are doing the same thing. Suffolk reported 11 fewer fatalities in the first six months of 1981 than in the same period last year, when the county's autoaccident deaths led the 62 counties in the state for the third consecutive year. Suffolk recorded 242 fatal accidents last year, up from 215 in 1979 and 200 in 1978, according to statistics compiled by the State Division of Motor Vehicles. The 242 accidents in 1980 resulted in 258 fatalities.

PARAMUS WHEN Lauren Valenta was 2 years old, doctors advised her parents that she had cerebral palsy and should be institutionalized because, as her mother recalled, there was ''nothing for her.'' Undaunted, the family moved from Sussex County to Bergen County largely because the latter had a program for such handicapped youngsters. Earlier this month, Lauren, who is now 6, was among the initial group of more than 100 students to be enrolled in the state's first regional day school for the multiply handicapped. The school occupies a new building in Paramus, and its opening might be said to represent as much of a meeting of challenges as Lauren's own. The school is the first of 11 regional facilities whose construction was given the go-ahead in 1973, when New Jersey voters approved a $25 million bond issue. Of the 10 other facilities, five are under construction (in Atlantic, Salem, Ocean, Middlesex and Morris Counties), three are scheduled (in Camden, Mercer and Hudson Counties) and bids have been received for the remaining two (in Essex County).

-------------------------------------------------------------------- ELLSWORTH E. ROSEN is a public relations executive in Boston with a summer cottage in South Wellfleet. ------- There is a special beauty to Cape Cod, in its wildness and expanse, in its shimmering calmness and fragility. One of the best ways to savor this beauty and to experience the different moods and sharp contrasts of the cape is to walk the trails of the Cape Cod National Seashore. There are 10 in all between Eastham and Provincetown, each combining fascinating vistas with opportunities to expand one's knowledge of man in nature. Generally gentle, almost gracious, the trails have been part of our family's life for almost two decades. The national seashore will mark its 20th anniversary this August, and our family has owned a beach house in the seashore from the inception. (Yes, one can own property in the 27,000-acre Cape Cod National Seashore. There are 2,000 houses, but no further building is allowed.)

A brick is not just a brick, especially when 1.4 million of them are needed for the new United States Embassy in Moscow. American experts carefully searched many countries for just the right brick to serve as a symbol of this nation in a foreign land, and in January they finally made their decision. The fine, pinkish-tan brick chosen for the facade of the Moscow embassy is being made in Augusta, Ga., by Merry Companies Inc. at a cost of $836,035.25. The price of shipping the bricks to the building site will be roughly $1 million. The Russians make plenty of bricks, but the color was off and the quality was judged to be poor, the experts said. American architects and State Department officials also looked in Finland, Sweden, Yugoslovia and Hungary for the right brick at the right price, without success.

In 1979 she took the track world and herself by surprise. Now Evelyn Ashford knows she can run fast. Earlier in the week, Miss Ashford set an American record in the 100-meter dash with the time of 10.90 seconds at a meet in Colorado Springs. Today during the National Sports Festival, the country's No. 1 women's sprinter ran a wind-aided 11.01 in winning on a newlysurfaced synthetic track that felt more like a soft cushion than a running surface. ''I couldn't get any force,'' Miss Ashford said, a sentiment shared by James Sanford, who won the men's 100 meters. ''I felt like I was standing still.''

O NCE again, the Japanese are coming, and on Wall Street, it is already being called ''the friendly invasion.'' This time, instead of invading American consumer markets with their Toyotas, Sonys and Panasonics, the Japanese are bringing their money. In increasing numbers, they are coming to buy stocks on Wall Street and to wheel and deal in America's commodities pits. For decades Japanese authorities, concerned with sheltering its economy, severely restricted the ability of Japanese to take yen out of the country. Last December, however, those stringent foreign exchange controls were substantially relaxed, and more Japanese funds are already flowing into American stock and commodity markets. Though the total is not yet great, investment professionals in both Japan and the United States predict far-reaching effects in both countries, not only in investment circles but also in broader economic, political and diplomatic spheres. The influx of Japanese funds is not only more business for Wall Street; it is also expected to enlarge, deepen and add liquidity to American financial markets. And in international finance, Japan's relaxing of currency controls is a kind of coming of age, elevating the yen as a major world currency and signifying Japan's willingness to expose its economy to the vagaries of world currency markets.

HARTFORD WITH $325 million in commercial office construction under way and more in prospect, business and civic leaders here are beginning to think about giving two of the city's most important public spaces a much-needed facelift. The Bushnell Park Foundation, established last spring, is seeking to raise much of the $2 million needed to restore that park, which lies between the business district and the State Capitol, by 1986, the 350th anniversary of Hartford's founding. And Riverfront Recapture Inc., organized in April, hopes to collect from $300,000 to $500,000 to restore public access to the Connecticut River, now walled off by 45-foot-high flood-control dikes and eight lanes of Interstate highway. Both efforts depend on a partnership between the large, affluent corporations here and the city government. ''In this city, there is quite a bit of precedent for this public-private partnership,'' Sanford Parisky, the vice president of the Bushnell Park Foundation, said, citing the restoration of the Old State House and the creation of the Civic Center with its shopping mall. Mr. Parisky is also the director of the Downtown Council, a corporate-sponsored group set up in 1974 to promote the city.