Although these textbooks are quite old, and some of the techniques described therein obsolete, these texts hold much practical value to the modern technician and engineer of instrumentation. ``First Principles'' of physics are timeless, regardless of the technology applied to them. Not only will the modern reader find much practical knowledge within these pages undiminished by the passage of time, but also fascinating insights into the historical applications of measurement and control.

**Mathematics**- Calculus Made Easy by Sylvanus Thompson, published in 1914. Written by a fellow with a keen sense of humor, this delightful book is sure to be an aid to all those striving to grasp the basic principles of differential and integral calculus. This text shows its age by its use of certain obsolete terms (``differential coefficient'' instead of the more modern ``derivative'' for example), but the concepts are timeless, and presented in marvelous simplicity. A modern reproduction of this book, updated by Martin Gardner, is currently published by St. Martin's Press.

**General Engineering**- Tables and Diagrams of the Thermal Properties of Saturated and Superheated Steam by Lionel Marks and Harvey Davis, published in 1920 by Longmans, Green, and Company. This is an easy-to-reference set of saturated and superheated steam tables, all expressed in British units (e.g. BTU, lb, degrees F) in 1 PSIA and 1 degree F increments. Pressures expressed in ``pounds'' are all PSIA (pounds per square inch absolute). The ``Total Heat of Steam'' (H or h) is otherwise known as enthalpy, expressed in BTU per pound mass. The superheated steam tables show the properties at the saturation temperature, then for 10 degree F increments of ``superheat.''

**Process Measurement**- Engineering Instruments and Meters by Edgar A. Griffiths, published in 1920. A fairly comprehensive book covering mechanical measurements (length, area, screw pitch, force and mass) as well as more common process variable measurements (volume, flow, velocity, temperature). Although the scan quality is excellent, the PDF file size is unfortunately very large.
- Pyrometry -- A Practical Treatise on the Measurement of High Temperatures by Charles Robert Darling, published in 1911. This fascinating text describes several different methods of temperature measurement including RTDs, thermocouples, and radiation (infrared) pyrometry. Of particular noteworthiness is the fact that many of the primary sensors described in this text remain essentially unchanged in modern form.
- The Measurement of High Temperatures by George Kimball Burgess and Henri Le Chatelier (third edition), published in 1912. One of the authors of this book (Le Chatelier) was a pioneer in the science of pyrometry.
- The Orifice Meter and Gas Measurement by Willis C. Brown and Malcolm B. Hall (first edition), published in 1921 by the Foxboro company.
- Measurement of Gas and Liquids by Orifice Meter by Henry P. Wescott and John C. Diehl (second edition), published in 1922.
- Flow and Measurement of Air and Gases by Alec B. Eason, published in 1919.
- The Venturi Meter by Clemens Herschel, published in 1895.
- Production and Measurement of High Vacuum by Saul Dushman, published in 1922 by the General Electric Company.

**Protective Relays**- Protective Relays by Victor H. Todd, published in 1922.

*Many thanks go to Google for serving as a repository of antique technical books. I first obtained many of the ebooks hosted here from Google's site:* http://books.google.com

United States government publications lack copyright protection, and therefore lie within the public domain.

- SR-71A flight manual, a document outlining many of the technical systems within the famous SR-71 "Blackbird" supersonic spy plane. This formerly classified military document was declassified and made available to the public at large. Many thanks to the "SR-71 Online" website (http://www.sr-71.org) for providing this document for download.