Applicable Mathematics in the 18th Century - Department of ...

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6. Later development of the bent-lever balanceFew examples of bent-lever balances made in the 18th century have survived. InEngland, we have some rare scales based on Patent Number 1014, obtained by J.S.Clais in 1772. They were made in London by the firm of Anscheutz and Schlaff, andall surviving examples were intended for weighing coins, not yarn or cloth.In Ludlam’s balance the graduations were engraved on a complete circular ring,but for most purposes a quarter circle or quadrant is sufficient. For this reason, aninstrument of this kind came be be known as a quadrant, which was slightly confusing,because there is an optical surveying instrument of that name. The earliest referencethat I can find to a quadrant for use in the textile trades is an advertisement forthe Glasgow firm of John Gardner [5], which appeared in the Glasgow Courier for 3March 1792. Among other types of balance, Gardner offered ‘quadrants for weighingcotton and linen yarn’.We can infer that quadrant balances were well known in the first part of the 19thcentury from the fact that at least two popular works on mechanics depict them.The diagram shown on the left in Fig.8 is taken from Kater and Lardner’s Treatiseon Mechanics [10], and the one on the right is taken from Moseley’s Treatise onMechanics Applied to the Arts [11], both published in the 1830s.Fig.8: Two quadrant balances illustrated in the 1830sNeither of these authors refers specifically to the weighing of yarn, and clearly thequadrant balance could be used for several purposes. For example, the new postalsystem introduced in the 1840s led to a massive increase in the use of scales forweighing letters. The stamp shown in Fig.9 depicts a Swiss postal scale made byLinder of Basel around 1860. (The date 1982 is the date of issue of the stamp.)10
Fig.9: Quadrant scale (c1860) for weighing letters, shown on a Swiss stampThe use of quadrant balances continued thoughout most of the 20th century. The‘Lancaster quadrant’ shown in Fig.10 was made by Goodbrands of Manchester, andwas widely used for weighing samples of cloth and yarn. More significantly, thebent-lever mechanism was incorporated in many other forms of weighing machine.Fig.10: A ‘Lancaster quadrant’, c1925.However, nothing lasts for ever, and over the last thirty years almost all mechanicalweighing devices have been replaced by electronic devices based on load-cells.References1. E. Baines. History of the Cotton Manufacture of Great Britain. London: Fisher& Co., 1835. (Reprinted Bristol: Thoemmes, 1999.)2. N.L. Biggs. A Tale Untangled: measuring the fineness of yarn Textile History35 (2004) 120-129.3. N.L. Biggs and J. Hutchinson. Knowles’ patent yarn balance. Textile History40 (2009) 97-103.11
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