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Slide Rule

“No engineering student would dare venture out in public…without his (or her) slide rule in its ‘holster’ and hanging from the belt,” recalls Professor Emeritus Wayne McMorran of California Polytechnic State University in his online history of that school’s electrical engineering department. “If you were really into it, you bought a really long one (about 20 inches) so you could get better precision.”

Slide rules were developed in England to allow multiplication by use of logarithms-a mathematical idea set out by Scottish mathematician John Napier in 1614. They ruled supreme for more than three centuries, widely used by engineers and navigators. Because the product of any two numbers is equal to 10 raised to the power of the sum of their logarithms, any multiplication problem can be more simply restated as an addition problem. With the rise of the mechanical slide rule, one could make these computations by positioning two ruled straightedges (or in some cases, circles), without having to look up numbers in a logarithm table.

In the early 1970s, cheap handheld electronic calculators vanquished slide rules. Although they are no longer manufactured, slide rules are still used in education: A slide-rule lending program run by Wichita, Kan., high school teacher Bill Cooper teaches important mathematical concepts that are crucial when using a slide rule, such as orders of magnitude and significant digits.

Reel Mower

Although lawn mowers call to mind the green grass oceans that surround modern suburban homes, the first one was patented in England in 1830 by Edwin Budding. Budding’s mower wasn’t driven by an internal combustion engine, of course; it was pushed along quietly, if effortfully, by the human operator. The cylindrical reel mower was displaced in the United States by the motorized rotary mower, part of the post-World War II crop of home-automation devices.

While the gasoline-powered mower is easier to push and cuts closer, it’s annoyingly noisy and generates bags of grass cuttings that are better left to mulch back into the lawn. It also belches pollution: The U.S. Environmental Protection Agency estimates that up to 5 percent of domestic air pollution comes from garden equipment powered by extremely inefficient two-stroke engines that burn both oil and gasoline. Another woe of the prevailing technology: A U.S. Consumer Product Safety Commission study reported 385,000 injuries from power mowers over a recent seven-year period, while reel mowers, although much less frequently used, caused no reported injuries at all during that time. Now re-engineered using more lightweight materials, reel mowers are making a quiet comeback; according to Michigan’s Department of Environmental Quality, sales of reel mowers in the past 15 years have more than doubled.

Automatic Watch

In 1780, Parisian watchmaker Abraham-Louis Breguet devised a timepiece that did not need to be wound; the everyday jostling of carrying the watch drove a pendulum that kept the watch running. This automatic watch was, in the words of modern-day poet David Slavitt, “a frugal wheel hoarding all human movement / for its own to spend at a jeweled leisure.” Early automatic watches, nestled in their owners’ watch pockets, didn’t get bounced around enough to work well. Only in the 1920s, when watches migrated to the more mobile wrist, did the automatic watch (also called “perpetual” or “self-winding”) become truly successful. One Swiss watchmaker, Rolex, became particularly well known by billing its watches as waterproof: Since the stem no longer needed to be used for winding, automatic watches were more resistant to water. The automatic watch did have to be worn daily in order to stay wound, but it was much less likely to wind down accidentally than earlier mechanical watches. It also kept time better, because the watch spring stayed at a rather consistent tension rather than winding down a great deal and then suddenly back up all the way.

Today, most people wear quartz battery-powered watches, which are accurate and can be made cheaply, but automatic watches are still successful in niche markets, including Rolex’s high-end market. Those mechanical watches that are still made today are largely automatic.


On May 6, 1937, as a stunned crowd looked on, Ferdinand Graf von Zeppelin’s majestic airship, the Hindenburg, exploded-a violent end for 36 human lives and also, since public faith in airships was destroyed, for a promising transportation technology. An earlier hard-shelled airship, the famous Graf Zeppelin (named for its inventor), could attain speeds of 130 kilometers per hour and in 1929 circumnavigated the globe in a record time of less than 22 days. Many dangers were associated with this transportation advance, though-the Hindenburg was only the most spectacular of numerous disasters.

While soft-sided blimps serve as flying billboards and camera platforms for sporting events, a German company, CargoLifter AG, plans to build an airship, the CL160, that could bear 160-ton loads across the ocean, which only boats might otherwise manage-buoyed by nonflammable helium, not the hydrogen that filled the Hindenburg. Plans call for a fleet of 50.

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