Instruction for Using a Slide Rule

for Using a Slide Rule, by W.
Stanley

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Title: Instruction for Using a Slide Rule
Author: W. Stanley
Release Date: December 29, 2006 [EBook #20214]
Language: English
Character set encoding: ASCII
*** START OF THIS PROJECT GUTENBERG EBOOK
INSTRUCTION FOR USING A SLIDE RULE ***

Produced by Don Kostuch

[Transcriber's Notes]
Conventional mathematical notation requires specialized fonts and
typesetting conventions. I have adopted modern computer
programming notation using only ASCII characters. The square root of

9 is thus rendered as squareroot(9) and the square of 9 is square(9). 10
divided by 5 is (10/5) and 10 multiplied by 5 is (10 * 5 ).
The DOC file and TXT files otherwise closely approximate the original
text. There are two versions of the HTML files, one closely
approximating the original, and a second with images of the slide rule
settings for each example.
By the time I finished engineering school in 1963, the slide rule was a
well worn tool of my trade. I did not use an electronic calculator for
another ten years. Consider that my predecessors had little else to
use--think Boulder Dam (with all its electrical, mechanical and
construction calculations).
Rather than dealing with elaborate rules for positioning the decimal
point, I was taught to first "scale" the factors and deal with the decimal
position separately. For example:
1230 * .000093 = 1.23E3 * 9.3E-5 1.23E3 means multiply 1.23 by 10
to the power 3. 9.3E-5 means multiply 9.3 by 0.1 to the power 5 or 10
to the power -5. The computation is thus 1.23 * 9.3 * 1E3 * 1E-5 The
exponents are simply added. 1.23 * 9.3 * 1E-2 = 11.4 * 1E-2 = .114
When taking roots, divide the exponent by the root. The square root of
1E6 is 1E3 The cube root of 1E12 is 1E4.
When taking powers, multiply the exponent by the power. The cube of
1E5 is 1E15.
[End Transcriber's Notes]

INSTRUCTIONS for using a SLIDE RULE SAVE TIME! DO THE
FOLLOWING INSTANTLY WITHOUT PAPER AND PENCIL
MULTIPLICATION DIVISION RECIPROCAL VALUES SQUARES &
CUBES EXTRACTION OF SQUARE ROOT EXTRACTION OF CUBE
ROOT DIAMETER OR AREA OF CIRCLE

[Illustration: Two images of a slide rule.]

INSTRUCTIONS FOR USING A SLIDE RULE
The slide rule is a device for easily and quickly multiplying, dividing
and extracting square root and cube root. It will also perform any
combination of these processes. On this account, it is found extremely
useful by students and teachers in schools and colleges, by engineers,
architects, draftsmen, surveyors, chemists, and many others.
Accountants and clerks find it very helpful when approximate
calculations must be made rapidly. The operation of a slide rule is
extremely easy, and it is well worth while for anyone who is called
upon to do much numerical calculation to learn to use one. It is the
purpose of this manual to explain the operation in such a way that a
person who has never before used a slide rule may teach himself to do
so.
DESCRIPTION OF SLIDE RULE
The slide rule consists of three parts (see figure 1). B is the body of the
rule and carries three scales marked A, D and K. S is the slider which
moves relative to the body and also carries three scales marked B, CI
and C. R is the runner or indicator and is marked in the center with a
hair-line. The scales A and B are identical and are used in problems
involving square root. Scales C and D are also identical and are used
for multiplication and division. Scale K is for finding cube root. Scale
CI, or C-inverse, is like scale C except that it is laid off from right to
left instead of from left to right. It is useful in problems involving
reciprocals.
MULTIPLICATION
We will start with a very simple example:
Example 1: 2 * 3 = 6
To prove this on the slide rule, move the slider so that the 1 at the

left-hand end of the C scale is directly over the large 2 on the D scale
(see figure 1). Then move the runner till the hair-line is over 3 on the C
scale. Read the answer, 6, on the D scale under the hair-line. Now, let
us consider a more complicated example:
Example 2: 2.12 * 3.16 = 6.70
As before, set the 1 at the left-hand end of the C scale, which we will
call the left-hand index