Slide rules, elegantly

March 01, 2003

ANYBODY GOT a Keuffel & Esser Log Log Duplex Decitrig lying around with your spare socks? You'll be amply rewarded for it on eBay or by one of the thousands of hobbyists around the world who trade in - slide rules.

Yes, slide rules.

Of all the collectibles in education - Dick and Jane books, protractors, erasers, boxes of chalk, desks, old crayons, compasses, even fountain pens - the slide rule is king. In a typical week, more than 500 of the mechanical calculating devices change hands on eBay at prices ranging up to $300.

Their attraction is understandable.

For one thing, the slide rule didn't fade out gradually, like the typewriter. When Hewlett-Packard Co. came out with the first electronic calculator 31 years ago, demand for the ruler-like device plummeted almost overnight. Thousands of slide rules were put away, forgotten until they were rediscovered and appreciated anew two decades later.

They were appreciated, as mathematicians and people of a certain age remember, for their elegance. The slide moved noiselessly as though mounted on a thousand tiny ball bearings or a base of very light oil. (It was the essence of coolness.) Scales - the figures along the length of the rule and on both sides of elaborate models - were engraved and ink-filled. Storage cases were often elaborate. (They're also collectibles.)

A good slide rule brought status. Men passed them on to their sons. Or, like mathematician Freeman A. Hrabowski III, president of the University of Maryland, Baltimore County, they held on to them, figuring one day the slide rule would rule again.

The slide rule, though, wasn't an item you gift-wrapped and presented to your sweetheart on Valentine's Day. Nor was displaying one prominently in a vest pocket a good strategy for landing a date with a cheerleader - unless she happened to be a fellow geek.

Mastering the rule was what moved the student beyond arithmetic to trigonometry and precalculus, a world of logarithms and sines that was Greek to the majority of kids. (In truth, they were secretly envious, and if they came of age in the Cold War, they knew the kids who could use a slide rule would save us from the Russians.)

A few slide rules are still manufactured, and you can find instructions on the Web for building and operating your own. Using a slide rule isn't a lost art. An expert with a quality instrument can multiply, divide and perform trigonometric operations (slide rules, curiously, can't add and subtract) more quickly than with an electronic calculator. Slide rule hobbyists hold contests to see who can calculate the fastest, who can beat the evil electronic calculator.

But it's not the quickness of the calculator that bothers Mr. Hrabowski; it's the automaticity.

"In the slide rule age," he says, "you were pushed to think critically about mathematics. Today, you push a couple of keys and get the answer without having to think about the problem. When a student gets an answer that just doesn't make sense, it's often because he used a calculator."

Some teachers reportedly are replacing calculators with slide rules, believing the rules encourage deeper thinking. But don't look for a comeback. Calculators, which a 1972 Hewlett-Packard users' manual introduced as "something only fictional heroes like James Bond, Walter Mitty or Dick Tracy are supposed to own," are ubiquitous. Kids are allowed to use them while taking tests in mathematics. They're installed in personal computers and laptops.

Slide rules will remain the stuff of nostalgia. But for nearly three centuries they contributed mightily to the store of human knowledge - all with a slip of the fingers and the cool slide of the rule.

Baltimore Sun Articles
Please note the green-lined linked article text has been applied commercially without any involvement from our newsroom editors, reporters or any other editorial staff.