## Chapter Topics

The first few chapters provide introductory material written for someone unfamiliar with the slide rule, although a certain level of basic math skill is assumed. Chapter 1 describes the mathematical framework that governs the use of slide rules in computations – the logarithm. While a deep understanding of the logarithm is not necessary to learn how to perform the basic operations of a slide rule, it is certainly of great help when trying to master them.

In Chapter 2, a *calculus*-based discussion of how values of logarithms can be computed numerically is presented. Again, knowing how to compute values of logarithms is not required before *using* such values to perform calculations. This chapter is included for completeness of the topic. Some of the results within this chapter may be of interest to the reader, even if the steps involved to arrive at those results may not be completely comprehensible to those not proficient in the mathematics being used.

Next, in Chapter 3, the various standard logarithmic scales found on the most common slide rules are described, as well as their use in performing calculations. These include scales used for multiplication and division, finding squares and square roots, performing trigonometric calculations, raising a number to an arbitrary power, and so on.

With a basic understanding of logarithms, how they are used in calculations, and how they are utilized on a slide rule, the following chapters delve into the slide rule collection itself. Chapter 4 presents the entire collection organized by major slide rule maker or groups of related makers. The lists provided here have further details of each rule and some information for each major slide rule maker. Links to photos of the rules are also included in the lists found in this chapter. On the other hand, Chapter 5 also presents the entire collection, but is organized in chronological order. The format of this chapter provides a quick, easy-to-navigate visual overview of all the slide rules.

In addition to the style and precision of the various makers, the large variety of slide rule types and models is indicative of the variety of scales and scale arrangements that can be found on them. Chapter 6 provides lists of the scale sets found on all of the rules in the collection.

Special groupings of items in the collection can be found in the various sections of Chapter 7. Here, one can quickly find the 25 oldest rules, the youngest rules, “beginner’s” rules, rules with the most number of scales, and other special listings. And Chapter 8 presents a number of historical books, manuals, and slide sheets that are also part of the collection.

Finally, in Chapter 9, a growing series of short *vignettes* can be found. These short articles and stories provide special insights and details of portions of the slide rule collection. This chapter is often expanded and updated, and the *vignettes* are not necessarily listed in the order in which they were written. The latest updates are listed at the beginning of the chapter.

Appendices are included which provide a brief time-line of the history of the slide rule, a listing of common slide rule scales, some statistics of the current collection, and a synopsis of the database used to create this document. A searchable table of the entire collection is also provided. References for each of the items in the collection are available, as well as links to other important introductory materials.

Tips for best navigating and viewing the site, including the use of its search tool and other features, are also provided.

The state of the collection is kept up to date through the use of a database maintained and processed using the **R** programming language (R Core Team 2021). A few details about the database can be found in Data Frame Properties. When changes to the database are made, the present document is automatically updated through the `bookdown`

package (Xie 2016) in **R** and re-posted.

Photographic images, figures, tables, and other graphics found throughout the text have been produced by the author unless otherwise noted. |

Errors, of course, are expected and acknowledged, as I am still learning while long-time devotees of the subject have much more knowledge than I about the slide rules and their history. I am deeply thankful for their tutelage and encouragement.