Slide rule with packaging, A W Faber 360, closed frame, double-sided slide, celluloid / wood / metal / glass / paper / cardboard, made by A W Faber, Bavaria, 1900-1905
Over the 19th and much of the 20th centuries the slide rule was the primary instrument for calculation used by many people engaged in the trades and in engineering. Although originally invented in the 17th century, and widely used for gauging (or estimating the quantities of certain products such as alcoholic spirits) it took until around 1850 for the slide rule to become generally popular with those for whom mathematics was a daily task. This was largely brought about through the increase in accuracy made possible by the development of the dividing engine and Amédée Mannheim's 1850 standardisation of the arrangement of scales utilised. His scales were the "C" and "D" scales, ranging from 1 (the index) to 10 and used for multiplication and division, and the "A" and "B" scales, ranging from 1 (the index) to 100 and used for squares and square roots.
New arrangements of scales appeared in the 20th century with the Rietz arrangement in 1902 and the Darmstadt arrangement in 1934. The Rietz scales added a log "L" scale, a "CI" or C inverted scale which was useful for calculations involving the reciprocal of a number, and the trigonometric scales: sine "S", tangent "T" and "ST" for the small angles were the sine and tangent are the same, to the front face of the stock. The Darmstadt arrangement added a series of Log-Log scales.
This slide rule was manufactured by A.W. Faber around 1900-1905 using the techniques that had been developed by the family company, A.W. Faber in Nurenberg, Bavaria. Slide rules manufactured by A.W. Faber and Faber-Castell were among the best made and most successful slide rules of the 20th century. The Faber company began as a maker of lead pencils in 1761 and expanded during the following century until in 1862 the then head of the company Lothar Faber was made a peer by King Maximilian of Bavaria, becoming Lothar von Faber. At this time the A.W Faber Company began to expand their product range. Lead pencils remained their main product until, in 1882, they commenced the manufacture of wooden slide rules using the Mannheim scales, selling them in Germany, France, England and the United States.
A.W. Faber stopped making slide rules in 1976 since the electronic calculator had taken over the market for hand-held calculating instruments.
Peter Hopp, Slide Rules, their History, Models and Makers, Mendham, New Jersey: Astragal Press, 1999.
http://www.answers.com/topic/a-w-faber-castell-unternehmensverwaltung-gmbh-co?cat=biz-fin - Company History: A.W. Faber-Castell Unternehmensverwaltung GmbH & Co.
Time Line for A.W. Faber and Faber-Castell
http://www.sliderulemuseum.com/SR_Dates.htm#Faber - Dieter von Jezierski, Slide Rules - A Journey Through Three Centuries (Astragal Press).
29 January 2008
There were generally two types of slide rules. One type were the linear slide rules consisting of a pair of strips of timber faced with celluloid (and in the mid-20th century, plastic) forming what is known as the "stock" and with a sliding strip inset between them. Of these there are two sub-types: closed frame, which is usually single-sided and appears as a single body of wood or plastic, and open frame, in which the stocks are separate but held together by straps usually of metal at each end of the body. The other type were the circular slide rules consisting of two or three concentric disks. Each type could have several sets of scales applied to them. Most slide rules have some kind of cursor which can be slid along the rule (or around the disk) acting as an indicator that assisted in lining up the slide scales with the scales on the stock.
This slide rule is of the linear closed frame type. It was manufactured by A.W. Faber in Bavaria and sold on the English market.