NEW YORK (NYT NEWS SERVICE ).- Ever since the compass was invented, perhaps around 2,000 years ago, humans have used Earth’s magnetic field to guide them. Many ages later, Sheldon Breiner devised ways to use magnetism to guide him to things that might otherwise never have been found — like sunken ships, a lost city and colossal basalt heads buried underground.

Breiner, a geophysicist, inventor and serial entrepreneur, started a company called Geometrics in 1969 that built sophisticated magnetometers, which measure magnetic fields (a compass is probably the most simple example of one). He then discovered how to use them to detect objects by observing the way the objects affect the magnetic fields that surround them.

Breiner had started employing rubidium magnetometers to detect seismic activity along the San Andreas Fault when he was studying geophysics at Stanford University. In time he harnessed magnetometers to search for mineral and oil deposits deep underground; find hidden weapons; locate skiers lost in avalanches; and help the government track down sunken submarines and a hydrogen bomb that fell into the ocean after a B-52 bomber collided with a refueling jet over Spain in 1966.

Breiner, who also founded companies that developed early applications for artificial intelligence and cross-platform software, died on Oct. 9 at his home in Portola Valley, California, near Palo Alto. He was 82.

His death was confirmed by his daughter, Michelle Driskill-Smith. She did not specify the cause.

Breiner used his expertise with magnetometers to help archaeological expeditions around the world peer deep below ground or water. He joined researchers looking for the wreckage of galleons off the coasts of California and Mexico and helped discover buried ruins that many archaeologists believe were part of Sybaris, an ancient city in Southern Italy that inspired the word “sybarite” because of the hedonistic lifestyle of its inhabitants.

On an expedition that began in the 1960s to San Lorenzo Tenochtitlan, a group of archaeological sites in southern Mexico, Breiner discovered scores of ancient artifacts, including two enormous basalt heads, one of which weighed about 10 tons, made during the Olmec civilization, which thrived as early as 1200 B.C. and vanished around 400 B.C.

Over several decades, Breiner returned to Mexico to keep searching. An article in The New York Times about an expedition to Laguna de los Cerros in 1998 described how he used a $25,000 cesium magnetometer attached to a pole to investigate an archaeological site.

“Carrying the pole, Dr. Breiner systematically marched through dense tick- and snake-infested brush, building a record of the magnetic variations at each point in Laguna de los Cerros,” the article said. “An assistant who wielded a machete walked in front of him, allowing the survey to be made in an array of straight lines.”

Breiner sold Geometrics to EG & G, a technology company and military contractor, in 1976, a transaction eventually worth around $45 million. He continued leading Geometrics until 1983, when he founded Syntelligence, an artificial intelligence company that designed software intended to replicate the wisdom of experts in fields like banking or insurance underwriting.

Syntelligence developed software that was marketed by IBM and worked with companies like American International Group and Bank of America, but the business did not catch on.

In 1989 Breiner founded Quorum Software Systems, which built software that allowed Apple applications to work with hardware made by other companies.

R. Martin Chavez, who founded Quorum with Breiner, devised a way for different operating systems to communicate with commands from Apple’s operating system without relying on Apple’s source code.

According to a 1992 article in Macworld magazine by the technology journalist Steven Levy, Apple initially approved of Quorum and even certified the company as a developer, but before Quorum released its software in 1992 Apple wrote a letter claiming that Quorum had infringed on its intellectual property, without specifying how.

Breiner knew that the letter and the threat of a lawsuit from Apple could ruin Quorum, which was seeking new funding. Before Apple could sue, Breiner filed a suit of his own, calling for a judgment that Quorum’s products did not violate Apple’s copyrights.

The two sides settled, and Quorum was allowed to continue developing its software.

Sheldon Breiner was born on Oct. 23, 1936, in Milwaukee to James and Fannie (Appel) Breiner. His parents, Jewish immigrants from Eastern Europe, later moved the family to St. Louis, where they owned a bakery.

After graduating from University City High School in St. Louis in 1955, he went to Stanford University, which had offered to pay for his education if he studied earth sciences. He earned bachelor’s and master’s degrees before completing his doctorate in the field at Stanford in 1967.

While at Stanford he met Phyllis Farrington, who goes by Mimi. They married in 1962. She and his daughter survive him, as do a son, David; a brother, Richard; and five grandchildren. Another son, Aaron, died in 1966.

Breiner began working with magnetometers long before he finished his education. He was so proficient with them that Varian Associates, a Silicon Valley company that made electromagnetic equipment, employed him while he was completing his master’s degree. He stayed at Varian until he started Geometrics.

Breiner also started a firm that helped oil companies accurately assess the amount of oil left in wells. He continued developing new ideas — he was recently working on an electronic signature verification system — and he also continued exploring. He returned to Mexico repeatedly to investigate the wreckage of a 16th-century galleon from Manila that he located in 2005.

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