September 15, 1981

In 1927, two French brothers lowered an electrical probe down an oil well on a wire and made a discovery as valuable as oil itself. Conrad and Marcel Schlumberger, who had been experimenting with using electricity to prospect for minerals, found that they could measure the electrical resistance of rock formations at various depths to obtain a picture of the underground geology. That process, known as well-logging, is now indispensible in drilling for oil, and highly profitable Schlumberger Ltd. has been the dominant company in the industry, with a 65 percent worldwide share of a $2.9 billion-a year business that is growing at more than 30 percent a year. Yet Schlumberger, which says it is not a well-logging company, is trying to expand its reach into what it considers is its actual field - data collection and processing.

MINNEAPOLIS BORN with a defective ability to form pigment, albinos are conspicuous people. Their whitish hair and skin and pale, squinting eyes often cause them to suffer more from social stigma than from their actual physical disabilities. In the hope of someday allaying the social and physical handicaps of albinos, scientists at the University of Minnesota are unraveling the intricacies of pigment formation, looking for an understanding that may help them correct the genetic flaws that cause the disorder. These defects afflict about one in 20,000 Americans, with the frequency higher in blacks than in whites. In all albinos, there is an absence or shortage of melanin, the pigment in skin that protects underlying cells and blood vessels from damage by ultraviolet radiation.

Inventories rose 1.1 percent for American manufacturers, wholesalers and retailers in July, the Commerce Department reported today, in a new indication of weakness in the national economy. Sales for July rose less than one-tenth of one percent and, as a result, the inventory-to-sales ratio climbed to 1.41, the highest level since last September's 1.43. The ratio means that it would take 1.41 months to sell off inventories at July's sales pace.

International Charges that toxic chemical weapons were used by the Soviet Union and the Vietnamese in Southeast Asia and possibly Afghanistan in violation of international agreements were backed up with evidence produced by the State Department. The evidence, which the department termed ''significant, although preliminary,'' relied heavily on analysis of one leaf-and-stem sample collected in Cambodia near the Thai border. (Page A1, Columns 1-2.) Russians will have to pay more for gasoline, vodka, jewelry and other ''nonessentials,'' the head of the State Committee on Prices announced. In explaining the increases, Nikolai T. Glushkov, said ''corrections'' in some prices were necessitated by ''conditions of production, the growing cost of the extraction of raw materials and the need to ensure the rational use of resources and certain commodities.'' Mr. Glushkov said the cost of ba sic foods would remainthe same and some commodities, such as medici nes, would be reduced. (A1:1.)

''Wouldn't it be funny,'' the White Plains woman said to her husband while ''antiquing'' Aug. 18 in Bucks County, Pa., ''if I found some of the jewelry I lost in the burglary?'' To her surprise, she did - a custom-made amethyst bracelet stolen, along with at least 75 other jewelry and silver pieces, only 10 days earlier from their home near the Scarsdale border. The thieves even took their tennis bags - presumably to carry the loot -but not their racquets. Arrest Follows Discovery On Aug. 20, using the couple as decoys, Manhattan detectives of the Special Frauds Squad arrested a previously convicted Bowery fence. They seized jewelry and silver estimated at nearly $500,000, including a dozen pieces the couple said were theirs.