The slide

It was a strange artefact to look at: a long, thin, rectangular block in a kind of ivory-like plastic, with a central tongue of the same material which could be moved lengthways, and a circumscribing band of transparent material, also movable.  On the surface of both sides of the block were hundreds tiny notches, some in black, some in red, some evenly spaced, and some like the diminishing steps of the Parkinsonian.  There were numbers, letters and a few words too, so the effect of the whole was of a new, bilingual Rosetta Stone, marked out in what looked like a hitherto unknown variety of the Irish Ogham alphabet and its presume translation.  It was a slide rule.

I first saw this complex device – made by a company called Faber-Castell, in Germany, of course – several decades ago in a stationer’s shop, along with all the other paraphernalia of adult tools such as precision pens of almost vanishingly small nibs, and obscure drawing implements whose function I could only guess at.  As soon as I saw it, I desired it.

I had wanted this cool, aloof, mysterious object partly because it seemed to be something to do with numbers, a subject I already loved, partly because I could feel – however obscurely and childishly – that it was a thing of real beauty, but mostly, I think because I sensed that it had something to do with power, the power born of knowledge and its application.  Above all, I desired that double mastery.

This probably explains the fact that once I received it for Christmas shortly afterwards, I never used it. Instead, it became a kind of talisman: to have it, to hold it, to touch it – these were enough to give me the power that I sought, the sense of occult potential.

But the potential only existed because I did, in fact, know how to unlock that power.  Despite the slide rule’s apparent complexity, its dizzying swirl of numbers and notches, the basic underlying principle was simple.  The slide rule allowed you to perform almost any arithmetical operation – multiplication, division; squares, cubes and their roots; sines, cosines, tangents; logarithms, exponentials – all by moving the central strip and the transparent slide one or more times, and reading off the result.  For example, to multiply 1.245 by 4.3, you just moved the central strip along until the figure 1 was above 1.245.  You then moved the transparent band’s central marker to 4.3 on the same strip, and read off the figure 5.355 below it – close to the calculator’s exact answer of 5.3535.

Of course, nobody uses slide rules today.  As the above example shows, the calculator is more accurate – and easier to use.  This would not matter much, were it not for the fact that most children – and adults – would not only be incapable of using a slide rule, they would also be unable even to understand its basic principles: the logarithmic scale – the Parkinsonian acceleration – because nobody bothers to comprehend that either.  So in the logarithm’s lapse and the slide rule’s slide is written a far greater and more terrifying loss and slippage: that of society’s numeracy skills. For most, the slide rule might as well be ivory carved in Ogham.  

(23.12.91)

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