Begin Following The Rules

A Substack Introduction

As a high school student taking science courses in the early 1970s, it was imperative to learn the operation of the standard slide rule. Invented in the early 1600s, the slide rule is a device that can be used to perform multiplication and division problems of numbers of a few digits, with an accuracy of a fraction of a percent, but without the need to resort to pen (or pencil) and paper. At first a novelty among the affluent, slide rules — invented in England — were soon used to compute the amount of boards that could be cut from fallen timber, and the volume (and taxation!) of alcohol found in a barrel of liquor. By the late 1700s slide rules found their way into the earliest design efforts of the steam engine, and were used in the calculations of iron bridge designs by the late 1800s. In the 1900s, slide rules were used in all science and engineering endeavors, eventually finding their way to the moon on the Apollo missions, and slide rules were even used to develop the electronic computers that soon replaced them.

Though electronic computers began to be developed in the 1950s and 60s, it was not until the release of affordable hand-held calculators in the mid-1970s that slide rules were no longer required on the job or in the classroom.

Of course by now those electronic calculators have been replaced by the “calculator apps” found on today’s phones and laptops. But electronic calculators (and phones and laptops as well) still require a power source, and early electronics could easily become damaged yielding an early mortality to the vintage calculators. A 200-year-old slide rule, on the other hand, still can work just as it did when it was produced.

A Carpenter’s Slide Rule from the early 1800s.

Thacher’s Computing Instrument, patented in 1881.

When it came to my high school studies, I still needed to use a slide rule for my homework and exams until graduation. But for Christmas my Senior year my wonderful parents made an amazing investment in my future — a Texas Instruments SR-50 Slide Rule Calculator. And once I left home that summer to go to college I never needed to use a slide rule again.

Production of slide rules around the world ceased within 1-2 years, and in the U.S. this occurred within a few months of January 1975. Then, 35 years after high school my wife and I found ourselves wandering about in antique stores and I eventually noticed that slide rules had become a real collectible item. Eventually I picked up a few – many of which I had never seen and knew little about – and I began to appreciate their intricate scales, precision construction, and the historical significance of their development. At this point, as a scientist and educator nearing retirement, I slowly began to gather more and more specimens and read and learn about their history.

During the COVID-19 pandemic I was beginning to phase into retirement and had quite a bit of new time on my hands. I had started a small web site with pictures of the slide rules I had collected, so I began to enhance the site to include further details about the history and uses of slide rules. The site, which I called Following The Rules, has grown into a unique resource to those interested in slide rules. But one thing the site lacks is a good feed-back mechanism. And now I have settled on the use of Substack to fulfill that need.

My goal is to introduce readers on Substack to these historically interesting items of computation and to encourage discussions that can lead to all of us learning more about the history and uses of their magical mathematical power.

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