# Give Me That Old Time Technology

Posted by: Stephen Wildstrom on February 21, 2007

I have recently renewed a long-time interest in old scientific instruments and, along the way, I think I have learned something interesting about today’s technology, compared to the way things used to be.

My latest acquisition, by way of of eBay of course, is a Keuffel & Esser Model 4092-3 log-log slide rule, a lovely mahogany and celluloid device 70 or so years old that works as well as it did they day it was bought. Lesson No. 1: Today we buy disposable technology. This stuff was built to last.

I’ve spent some time reacquainting myself with the slide rule, a tool I last used in high school. I am struck by how it is simultaneously elegantly simple and very sophisticated. Provided you are prepared to settle for no more than three digits of precision, even badly out of practice I can probably do a compound interest calculation on the log-log scales faster that I could in Excel or on my HP 12c financial calculator.

Lesson No. 2: Technology used to be transparent. I have only the vaguest idea of how an electronic calculator works, and that's a lot more than most people. But the theory and practice of the slide rule, even those tricky log-log scales, should be readily understandable to a student who has made it through high school precalculus. We trust our lives daily to devices of whose workings we have no understanding whatsoever. I'm not sure this is a good thing.

My other recent acquisition, also through eBay, was an instrument more obscure and even more marvelous than the slide rule. It's called a compensating polar planimeter, also by Keuffel & Esser, and it's used to measure the area enclosed by a curve, for example, the area of a lake on a map.

Looking at a planimeter, it's far from clear how it works or even what it does. But the K&E manual helpfully includes a section on the theory of its operation. (For the mathematically inclined, the planimeter is based on Green's Theorem, which relates the area bounded by a curve to the line integral of the boundary.

Planimeters, unlike slide rules, are still made and used, but the contemporary ones are, of course, electronic rather than mechanical and, like all electronic devices, their workings are inscrutable. My half-century old version has never needed batteries and, if you use it with a careful and steady hand, can measure areas to one one-hundredth of a square inch.

Lesson No. 3: Our new digital tools are faster, usually cheaper, and require much less skill to use than their mechanical predecessors. But I can't help but think that we have lost something valuable in the process.