Gunter's Scales, Group of 2

These two 2' boxwood rules are identical to each other and to MA.319077 and MA.318174. The top of one side has a scale of inches, divided to tenths of an inch and numbered by ones from 23 to 1. On the left are 10" and 9" (divided to 1/2") plotting scales with diagonal scales at each end. In the middle are scales for rhumbs, chords, sines, tangents, and semi-tangents. On the right are scales for leagues, rhumbs, miles of longitude, and chords. Brass pins at the zero and 60° marks reduce wear from the points of dividers, which were used to transfer measurements between the scale and the user's drawing.

The other side has logarithmic scales: sines of rhumbs, tangents of rhumbs, line of numbers, sines of degrees, versines of degrees, and tangent of degrees. At the bottom edge are a meridional line and a scale of equal parts that divides 23" into 17 sections. The sections are numbered by tens from 60 to 10 and from 100 to 0.

The first rule is marked on the first side in the lower right corner: BELCHER BRO^S. & C^o. NEW – YORK. Thomas Belcher began making rules in New York in 1821 and was joined by his brother, William, in 1825. Around 1831 another brother, Charles, joined the firm, and the company's name was changed from T. & W. Belcher to Belcher Brothers. Around 1843 manufacturing of rules moved to New Jersey and the firm went by the name Belcher & Bros. Around 1853 some of the men's sons joined the firm, and the name was changed to Belcher Bros. & Co. The first rule dates to this period. The company had become the largest American manufacturer of rules, but it was surpassed by Stanley in the second half of the 19th century. Belcher stopped manufacturing rules around 1877.

The second rule is unmarked. Key points around the scales are marked with suns, unlike the asterisks on the first rule; the abbreviations for the scale labels are different; and the bottom edge is beveled at a sharper angle than the bottom edge of the first rule. These differences indicate that the second rule was manufactured by a different firm. This rule also has pencil marks on the top and bottom edges.

References: Otto van Poelje, "Gunter Rules in Navigation," Journal of the Oughtred Society 13, no. 1 (2004): 11–22; Belcher Bros. & Co.'s Price List of Boxwood & Ivory Rules (New York, 1860; reprint, Fitzwilliam, N.H.: Ken Roberts Publishing Co., 1982); Philip A. Cannon II, "The Makers and Markers of Gauges, Rules, Squares, and Tapes," http://www.pactu.com/makers.htm.

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