Instruction for Using a Slide Rule

for Using a Slide Rule, by W. Stanley

Project Gutenberg's Instruction for Using a Slide Rule, by W. Stanley This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org
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 of the C scale, over 2.12 on the D scale (See figure 2). The hair-line of the runner is now placed over 3.16 on the C scale and the answer, 6.70,