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# Instruction for Using a Slide Rule

## by: W. Stanley

Publisher:
DigiLibraries.com

ISBN:
N/A

Language:
English

Published:
1 month ago

Downloads:
1

#### Categories:

#### Description:

Excerpt

[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 square_root(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

, 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

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, read on the D scale.

METHOD OF MAKING SETTINGS

[This 6 inch rule uses fewer minor divisions.]

In order to understand just why 2.12 is set where it is (figure 2),

notice that the interval from 2 to 3 is divided into 10 large or major

divisions, each of which is, of course, equal to one-tenth (0.1) of the

amount represented by the whole interval. The major divisions are in

turn divided into 5 small or minor divisions, each of which is one-fifth

or two-tenths (0.2) of the major division, that is 0.02 of the

whole interval. Therefore, the index is set above

2 + 1 major division + 1 minor division = 2 + 0.1 + 0.02 = 2.12.

In the same way we find 3.16 on the C scale. While we are on this

subject, notice that in the interval from 1 to 2 the major divisions are

marked with the small figures 1 to 9 and the minor divisions are 0.1 of

the major divisions. In the intervals from 2 to 3 and 3 to 4 the minor

divisions are 0.2 of the major divisions, and for the rest of the D (or

C) scale, the minor divisions are 0.5 of the major divisions.

Reading the setting from a slide rule is very much like reading

measurements from a ruler. Imagine that the divisions between 2 and 3 on

the D scale (figure 2) are those of a ruler divided into tenths of a

foot, and each tenth of a foot divided in 5 parts 0.02 of a foot long.

Then the distance from one on the left-hand end of the D scale (not

shown in figure 2) to one on the left-hand end of the C scale would he

2.12 feet. Of course, a foot rule is divided into parts of uniform

length, while those on a slide rule get smaller toward the right-hand

end, but this example may help to give an idea of the method of making

and reading settings....