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Teach Yourself Sliderule

Text of Teach Yourself Sliderule

Teach Yourself the Slide Rule

TEACH YOURSELF THE SLIDE RULE The "Teach Yourself ..." series of books (still published today by Hodder Stoughton) will be familiar to any British reader. One of their titles was "Teach Yourself the Slide Rule" by Burns Snodgrass M.B.E, A.R.C.Sc.. The author had founded the Unique Slide Rule Company in 1920. The book was published in 1954, the year of his death. The company was subsequently managed by his son. Given the provenance of the author, it is not surprising that the book concentrates on Unique slide rules. However since the company produced a wide range of rules it made a very comprehensive book. The book was originally published by "The English Universities Press Ltd". The copyright is now held by "Hodder Stoughton", to whom I am grateful for permission to scan parts of the book and put them on this web site. The following is the original list of contents. From those sections with hyperlinks you can see which of them have been scanned and added to my site. I should add that I have not simply scanned the pages and put them on the site as a graphics images but have interpreted them by Optical Character Recognition. The advantage of this is that the files are smaller than the original graphics image and can be more easily printed. The disadvantage, but only for me, is that it is more labour intensive. I have also at times modified the format (for example moving lists of slide movements into tables). As an Engineer married to an English graduate, I have been made aware that not only do engineers sometime use language in an idiosyncratic way but they are not always consistent in their use of language; this was case with Burns Snodgrass. I have not tried to improve his English nor add consistency (for example, descriptions of slide movements are sometimes given on separate lines and sometimes run together and separated by commas). The figures were taken from the original book; they often showed the two ends of a rule split over two pages. Contents FORWARD SECTION 1. THE PRINCIPLE OF THE SLIDE RULE Linear and non-linear scales - numbering of the scales - reading the scales - multiplication and division of simple numbers. SECTION 2. FRACTIONS-DECIMALS Fractions, addition and subtraction - Multiplication and division - Decimals, Conversion of Decimal Fractions into ordinary Fractions - Addition and Subtraction - Multiplication and Division - Contracted methods - Conversion of ordinary Fractions into Decimal Fractions - Recurring Decimals - Conversion of Recurring Decimals into ordinary Fractions. SECTION 3. THE MODERN SLIDE RULE Protection of the Slide Rule - Component parts - C & D Scales - A & B Scales - Log Scale - The Cursor - Linear Scales. SECTION 4. C & D SCALES Multiplication - Division - Multiplication and Division combined - Position of a Decimal Point. SECTION 5. A & B SCALES Squares and Square Roots - Cubes and Cube Roots - Cube Scale. SECTION 6. LOG LOG SCALES Evaluation of Powers and Roots - Common Logarithms - Natural Logarithms. SECTION 7. THE TRIGONOMETRICAL SCALES Sine Scale - Tangent Scale - Solution of Triangles - Navigational Problems - Navigational Units and Formulae - Wind and Drift Problems - Interception Problems - Calculation of True Track and Distance. SECTION 8. THE COMMERCIAL RULE The Special Commercial Scales-Money Calculations - Discount Scale - The Monetary Rule - .s.d. Scales - Invoicing calculations. SECTION 9. THE PRECISION RULE The Special C & D Scales - Multiplication - Division - Determining in which scale lies the answer. SECTION 10. THE ELECTRICAL RULE Dynamo and Motor Efficiencies - Volt Drop - Duplicate C & D Scales - Reciprocal Scale - Time Saving.file:///D|/SlideRules/WebPage/pdf/htm/tys.htm (1 of 81) [02/09/2001 20:59:44]

Teach Yourself the Slide Rule

SECTION 11. THE DUALISTIC RULE Duplicated C & D Scales - Special 20" Scales for ordinary calculations - Squares and Square Roots - Cubes and Cube Roots - Log Log Scales. SECTION 12. THE BRIGHTON RULE The ordinary Scales - Log Log Scales - Sine & Tan Scales - Cube Scale - Log Scale. SECTION 13. INDICES & LOGARITHMS Indices - Multiplication and Division - Logarithms - Reading Log Tables - Multiplication and Division - All Bilogarithms - Powers and Roots - Logarithms with Negative Characteristics - Tables of Logarithms and Antilogarithms. SECTION 14. OTHER CALCULATING INSTRUMENTS Cylindrical Calculators - Circular Calculators - Watch type Calculators - Other Rules. SECTION 15. HISTORICAL NOTE Invention of the Slide Rules - Degree of Accuracy - Common Gauge Points - Marking Special Gauge Points. SECTION 16. EXERCISES Commerce - Energy and Power - Friction and Heat - Strength and Deflection of Beams - Strength of Shafts and Deflection of Springs - Electricity - Building - Surveying - Navigation Miscellaneous. ANSWERS TO PROBLEMS

FOREWORD THE present era is sometimes termed the mechanical age because so many operations which, in earlier days, were carried out slowly and often painfully by hand, are now performed by machines with an enormous saving in time and effort. The slide rule cannot be regarded as a modern invention since the first design dates from the early part of the seventeenth century, but every year sees additions and variations made and the up-to-date instrument has, as might be expected, advanced greatly beyond the earlier types. Every year a considerable number of Patent Specifications are lodged in the British Patents Office to give protection to the latest inventions in slide rule technique, and we may say fairly that the slide rule in its own field is keeping pace with modern mechanical advance. This Teach Yourself Book is published to increase the popularity of the slide rule. It is hoped that it may help to remove the fallacy that there is something difficult or even mysterious connected with a simple instrument with which everybody who has calculations to make should be acquainted. Among the technicians and artisans upon whom we so much depend for the maintenance and improvement of national prosperity, are many who have frequently to make calculations. They would be hampered in their activities if the improvements we have referred to had not extended to expediting their work. The slide rule and other instruments which give the same facilities for rapid calculations, are covered by the term "Mechanical Calculation". It is unfortunate that, for some reasons not easy to see, the slide rule is sometimes regarded as a difficult instrument with which to become proficient. There is a tendency for some people to become facetious in their references to this simple instrument. Journalists and broadcasters are great offenders in this respect and some of their references are unbelievably absurd and show a lack of elementary knowledge. The clumsy and unscientific system of monetary units and measures in weights, lengths, areas, etc., which have grown up and are still used in this country, give some slight difficulty in applying the slide rule to calculations in which they are involved and since the scales of slide rules are, in most cases, subdivided in the decimal system, any notations of weights and measures which are similarly designed, such as the metric system, lend themselves readily to calculation by slide rule. We shall find, however, that when working in our monetary system of pounds, shillings and pence, or in lengths in miles, yards and feet, or in any of our awkward units, the slide rule can be employed to simplify our work and give results quickly, and with a degree of accuracy sufficient for practical requirements. We have said that, in general, slide rule scales are subdivided in decimal fractions, and since there are still some people who cannot easily calculate in the decimal system, we give at an early stage a simple explanation of the principles of this system. Perhaps we need hardly add that any sections of this book which deal with matters with which the reader is quite familiar may be glanced at and passed over.file:///D|/SlideRules/WebPage/pdf/htm/tys.htm (2 of 81) [02/09/2001 20:59:44]

Teach Yourself the Slide Rule

We shall find that the underlying principle of the slide rule is calculation by logarithms. Just as a man may be an expert motor-car driver without understanding the principles of the internal-combustion engine and the mechanism of his car, so can a slide rule be used without the slightest knowledge of logarithms. In fact, we hesitated at including the section on logarithms, in case the mention of the term might cause discouragement and increase the sense of awe with which some people regard the slide rule. The section on logarithms may be disregarded entirely, and indeed we ask that it should be, on the first reading of this book, but when the rudiments of the slide rule have been mastered - and again we stress the simplicity of these - it may be that some readers will find interest and advantage in learning something of the first principles of "logs" - one of the most fascinating parts of elementary mathematics. Another factor which has contributed to the reluctance of people to purchase a slide rule lies in the erroneous impression that it is a costly instrument. Naturally enough, people are averse to paying two or three pounds for an instrument which they fear may be of little use to them. Inexpensive slide rules have been available in this country for over thirty years, and their makers claim that for accuracy and utility they are equal to the more expensive varieties which have been manufactured for a much longer period. The first "Unique" slide rule, the 10" log-log model, was produced at a popular price for students. Its introduction was welcomed, and it met with success. There are now about a score of different slide rules in the "Unique" range, and sales have progressively increased, and it may fairly be said that this make of rule is now the "best seller