Walter Shawlee, the ruler of slide rules, has died at the age of 73

For approximately 350 years, humanity’s most innovative portable computer has been the slide rule. Just as typewriters once symbolized the writer, slide rules symbolized the engineer.

These analog calculators were made of metal, wood, plastic, and even bamboo and could be found all over the world. Their functions included calculating higher-order multiplications, exponents, and logarithms, among other mathematical operations. They were usually long and rectangular with a retractable central segment and featured dense fields of letters, lines and numbers stacked on top of each other.

They seemed almost comically abstruse, as if they could be used as paddles in a math fraternity’s hazing rituals.

Non-nerds struggled to make sense of them. Then, in the early 1970s, lightweight electronic calculators became widely available. The market for slide rules collapsed and production of new devices essentially ceased.

One day, about 20 years later, a middle-aged avionics engineer named Walter Shawlee was rummaging through a drawer in his home in Kelowna, a medium-sized city in British Columbia, when he came across his old slide rule from high school.

It was a Keuffel & Esser pocket Deci-Lon, model 68-1130, with a thin Ivorite body and a delicate clear slider box. Both had stood the test of time. Mr. Shawlee recalled that as a teenager he spent six months saving money to buy it.

Inspired by this encounter with his youth, he created a website dedicated to slide rules. Before long, nostalgic math wizards from decades past stumbled upon the site. Emails poured into Mr. Shawlee’s inbox. He began spending eight hours a day researching, buying, repairing and reselling old slide rules.

“Are you trying to conquer the slide rule market?” his wife, Susan Shawlee, asked him nervously in the Wall Street Journal reported in 2003.

The Institute of Electrical and Electronics Engineers’ journal, Spectrum, determined in 2007 that Mr. Shawlee had, in effect, “cornered the world market.”

“It’s Mr. Slide Rule,” a Texas engineer and slide rule enthusiast told the Journal. “Walter knows everyone in the slide rule racket.”

Mr. Shawlee died Sept. 4 last year at his home in Kelowna. He was 73 years old. His death was not widely reported at the time and the New York Times was only made aware of it last month. His wife said the cause was cancer.

Mr. Shawlee was not simply a sentimentalist with a slide rule, a slave to the memories of adolescent geekdom. He argued that slide rules had an intrinsic appeal for several reasons.

He saw dignity, for example, in their solidity and design. In a 1999 Times profile, Mr. Shawlee described slide rules as “the technological version of a broadsword.” We his website, the Universe of the slide rule, contrasted them with digital technology. “In 50 years, the computer you use to view this web page will be a landfill,” she wrote, “but your trusty slide rule will simply be broken in!”

For Shawlee, the lost durability represented by slide rules belonged to a larger narrative of decline. “When we used slide rules every day in the 1960s, we were able to put people on the moon,” Shawlee told the Journal. Speaking to the Times, she observed: “People who grow up with calculators have no number sense.”

Joe Pasquale, a professor of computer science and engineering at the University of California, San Diego, gave lectures on the “history, theory and practice” of slide rules, including a review of the “largest slide rules ever made,” as he put it it in a description of the race.

In an email, Professor Pasquale explained the pedagogical value of slide rules. Calculators tend to replace the human mind, requiring users only to enter numbers and “blindly accept” a result, leading to a loss of the user’s ability to calculate – “and, more generally, to think,” he wrote Professor Pasquale. while slide rules require active involvement, he added, “extending the mind’s calculating capacity.”

It was Mr. Shawlee’s good fortune that a surprising number of people shared these views. In the early 2000s he was making $125,000 a year repairing and reselling slide rules. The company paid for his two sons’ college tuition and sent one of them to law school. Its customer base has taken its most organized shape the Due Companya club named in honor of William Oughtred, the Anglican minister generally credited with inventing the slide rule in the early 1620s.

Mr. Shawlee’s website has developed a subculture of its own, with a network of slide rules from Arizona to Venezuela to Malaysia digging on Mr. Shawlee’s behalf through the moldy wares of old stationery stores, estate sales and school district warehouses looking for the slide rules. In Singapore, a civilian employee, Foo Sheow Ming, visited the back of a bookstore and found 40 unopened crates containing more than 12,000 slide rules in several varieties. On his website, Shawlee called the discovery “the absolute El Dorado of slide rules,” and Foo told the Journal it was “mainstream.”

Due to government regulations prohibiting profiting from the merchandise, Mr. Foo sold the slide rules to Mr. Shawlee at a discount. “It’s all about the thrill of the hunt,” he told the Journal.

Including Mr. Shawlee’s inventory notable artifacts of the history of science. He offered a slide rule made for machine gun operators, with calculations for wind, elevation and range. It offered a slide rule for measuring metabolic rates, with different settings for age, gender and height. And she has used her website to explore the ins and outs of the slide rule, writing, for example, about slide rules made by the US government to calculate the effects of nuclear bombs.

“Do you need to know the optimal blast height for that new atomic bomb you just bought?” Mr. Shawlee asked in a mock sales presentation. “How about the radius of the high-confidence kill zone, or the temperature at an exact distance from the nuclear weapon that just exploded on the block? These kids can answer all those burning questions as you get blasted into free ions and radioactive dust at about 1,300 mph”

He also sold slide rule cufflinks and tie clips, which in some cases were made by major slide rule manufacturers as promotional items during what Mr. Shawlee called “the golden age of slide rules.” Tie clips proved so popular in the slide rule universe that Mr. Shawlee worked with a small foundry to start making them himself.

Over time, its customers included a weather station in Antarctica, where many electronic gadgets couldn’t withstand the cold; photo editors responsible for adjusting the size of images (they like the slide rule for clearly displaying different values ​​for the same ratio); an archaeologist who discovered that calculators became too dusty to function properly during excavations; the pharmaceutical company Pfizer, which gave away slide rules at a trade show; slide rule enthusiasts in Afghanistan and French Polynesia; and “NASA guys,” Mr. Shawlee said Engineering Times in 2000.

Walter Shawlee II was born on November 27, 1949 in Los Angeles. Her mother, Joan (Fulton) Shawlee, was an actress best known for playing Sweet Sue, the “girl band” leader at the center of the film “Some Like It Hot” (1959), and for playing Pickles Sorrell, a character recurring on “The Dick Van Dyke Show” (1961-66). His father was a hotel concierge and painter specializing in marine scenes.

At 14, Walter worked in an electronics store and devotedly read magazines such as Electronics World. He studied engineering and mathematics at the University of California at Los Angeles before dropping out. He held several jobs, including as an assembly line welder at a Volvo plant in Sweden, before founding Northern Airborne Technology, a successful aviation communications company, in Kelowna. He sold the company in 1992.

Later, he became a tinkerer and inventory taker for hire, helping companies design, for example, machines that can delicately apply labels to a variety of fruits. He repaired and sold gadgets including signal generators, high-voltage rectifiers and cathode ray tubes.

He and his wife first met at UCLA and married in 1971. In addition to her, he is survived by their children, Walt III and Rose Shawlee, and a half-sister, Angie Barchet.

When the Journal visited the Shawlee home, there were about 1,000 slide rules strewn across the dining table, in Mr. Shawlee’s office and in the family sauna. “I know my wife would like to have her dining room back soon,” she told Spectrum magazine.

In a telephone interview, Ms. Shawlee said thousands of devices were still in the family home. She said she intended to continue selling them. As far as you know, there is no prospect of another collector-expert-fixer-dealer-romantic like Mr. Shawlee emerging in the “slide rule racket.”