Annals of High Tech: The Slide Rule

At the risk of being characterized as an old fart, WC introduces a sometime feature describing various items of technology that were state of the art in his lifetime, but have also vanished in his lifetime. Think of it as a chronicle of change.

We’ll start with the slide rule. Invented by Reverend William Oughtred in about 1622, who utilized John Napier’s work on logarithms and Edmund Gunter’s work on logarithmic scales, the slide rule was a mechanical analog computer. Slide rules were ubiquitous by the 1960s; one went to the Moon with Buzz Aldrin.

A typical ten-inch student slide rule (Pickett N902-T simplex trig) (via Wikipedia)

A typical ten-inch student slide rule (Pickett N902-T simplex trig) (via Wikipedia)

They were indispensable to any science student; WC owned a Simplex1 very like this one, purchased at the old Yukon Office Supply in 1968 for about $40.00, probably $100 adjusted for inflation. It was especially important for Chemistry class; the one time WC forgot to take it to class Prof. Swinehart (yes, really) sprang a pop quiz on us.2

Really, the slide rule was doomed from the moment of the invention of the transistor in 1947. From that point, it was a matter of shrinking the transistor and economies of scale. The pocket calculator – more accurate, faster and it handled the orders of magnitude that the slide rule left to the user – began to supplant the slide rule in the early 1970s. The last slide rule was manufactured by Keuffel & Esser on July 11, 1976. In 1978, WC bought an early HP calculator (an HP 18)3 and his slide rule was consigned to the bottom drawer of his desk. Computer spreadsheets also contributed to the demies of the slide rule.

Today they are a collector’s item. There is a collectors’ club, called the Oughtred Society, and a slide rule museum. There’s some irony that calculations leading to the digital pocket calculator were made on the slide rule. From indispensable to completely obsolete in a very few years.


  1. Fifteen dollars on eBay
  2. WC apologizes again to RKY for barging into the dorm room to get that slide rule at an, ah… awkward time for RKY. My mistake. 
  3. WC was an enthusiastic HP programmable calculator user, at one point owning a powerful HP 41C with memory cards, a printer and function cards. It was an expensive habit, and led to even more expensive computer hardware. 

5 thoughts on “Annals of High Tech: The Slide Rule

  1. Nothing wrong with being an old fart. These days I consider it a plus…

    I still have my yellow Del N903-ES and yes it’s in my desk drawer a foot to my right. Haven’t used it since the early 70’s but I sure as hell won’t throw it away.

  2. I have Dad’s Post slide rule from his college days, 1935. My favorite is a pocket circular from Concise, by Sama & Etani. Diameter of 2.375″, so equal to a 7.5″ straight rule. It also had reference tables of conversions and a periodic table.

  3. You want irony? You want old fart? I used a K&E slide rule from 70-72 while obtaining an MS in Computer Science😀

    • 1970-72 was back when a computer science student made votary offerings in the form of stacks of paper punch cards to the high priest graduate students at the temple of Fortran. Slide rules were much faster and, often as not, more accurate.


  4. Does your HP41C have that motorized card reader? I think I still have on its memory card the program I devised to turn 5K, 10K and marathon run times into per-mile splits – back and forth – and so on….

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