[GreenKeys] slide rule???

[Craig Sawyers]

> And Where to put the @#$%^@&* decimal point!
>
> Gil, W1RG

I think there is a lost skill in that statement of frustration - making an
order of magnitude estimate.  Roughly how big is the answer?  You had to do
that sum, either in your head or with a quick paper calculation to work out
where the decimal point went with a slide rule.

Alas nowadays that very useful engineering skill is almost no more - grab
the calculator and crunch the numbers.  And if you push the wrong keys, you
have no hint that the answer might be wrong.  With the slide rule, if the
rough calculation gave 5 x 10^8, and you got a result of 1.23 from the rule
you at least had an idea that you had a problem and ought to rerun the
maths.

Craig