By Charles Knell – Above is a picture of a slide rule. This is what engineers and scientists used before electronic calculators were invented. In 1969, many of the calculations required to land men on the moon were performed on these. I used one in high school chemistry, physics and when I attended engineering college. You could use it for multiplication, division, trigonometric functions, logarithms, and more. They don’t add or subtract so we had to do that on paper. The one I bought for college came with a leather case which you could wear on your belt. However, doing this was like wearing a sign that said, “engineering student”. So, I carried mine in my briefcase. It was made of bamboo laminated with engraved plastic. It still slides like a dream. A great slide rule doesn’t stick when you move the slider and bamboo is great for the purpose. Check out this link to see how a slide rule makes calculations. Or, the manual for mine is here.

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