Accession No

1605

Brief Description

Gunter scale; English; post 1772

Origin

London; England

Maker

Class

mathematics

Earliest Date

1772

Latest Date

1820

Inscription Date

Material

wood (boxwood); metal (brass)

Dimensions

length 611mm; breadth 41mm

Special Collection

Provenance

Purchased from Saul Moskowitz Instrument Engineering, 6 Mugford Street, Marblehead, Mass. 01945, U.S.A., in 1971. Catalogue Historical Technology, Fall 1971, no.103, item 20.

Inscription

‘Navigation Scale Improved By. B. Donn’ (obverse)

Description Notes

Boxwood Gunter scale with bevelled edge. All numbers punched.
Obverse scales:
1. ‘GUNS DIAMR’ for weight of shot with respect to bore on scale beneath. Divided 1 - 42, numbered 1, 1 1/2, 2, 3, 4, 6, 9, 12, 18, 24, 32, 42.
2. Scale of inches divided [0] - 24, numbered by 2, subdivided to 0.1.
3. Scale of two feet in 200 equal parts, divided [0] - 200, numbered by 10, subdivided to 1.
4. 10-inch scale with transversal scale for division to hundredths.
5. Scales of equal parts to the inch for tenths, fifteenths, 1/20, 1/25, 1/30, 1/35, 1/40, 1/45, 1/50 and 1/60, each divided [10] - [0] - 10[0], numbered by 1[0] with first division subdivided to 1.
6. Scale of rumbs marked ‘Rumb’ divided [0] - 8, numbered by 1, subdivided to 0.25.
7. Scale of chords marked ‘Chord’ divided [0] - 90˚, numbered by 10˚, subdivided to 1˚.
8. Scale of sines, marked ‘Sine’ divided [0] - [90˚], numbered by 10˚ to 70˚; 0 - 20˚ subdivided to 1˚; 20˚ - 70˚ subdivided to 2˚; 70˚ - 80˚ subdivided to 5˚.
9. Scale of secants, marked ‘Secants’ divided [10˚] - [79˚ 45´]; 20˚ - 70˚ numbered by 10˚; 70˚ onwards numbered by 1˚; 10˚ - 20˚ subdivided to 5˚; 20˚ - 40˚ subdivided to 2˚; 40˚ - 60˚ subdivided to 1˚; 60˚ - 70˚ subdivided to 30´; 70˚ onwards to 15´.
10. Scale of tangents marked ‘Tange’, divided [0] - 80˚, numbered 10, 20...70, 71, 71..80; 0 - 60˚ subdivided to 1˚; 60˚ - 70˚ subdivided to 30´; 7˚ onwards subdivided to 15´.
11. Scale of semi-tangents marked ‘S. Tang’, divided [0] - 160˚, numbered by 10˚; 0 - 120˚ subdivided to 2˚; 120˚ - 140˚ subdivided to 1˚; 140˚ onwards subdivided to 30´.
12. Scale of ‘M. Lon’ divided [0] - 60, numbered by 10, subdivided to 1.
13. Scale of chords marked ‘Chord’, divided [0] - 90˚, numbered by 10˚, subdivided to 1˚.

Reverse carries log scales.
1. ‘S. Rumb’ (semi rumbs?) divided [0.5] - 8, numbered by 1, subdivided to 0.25.
2. ‘Numb Sqr’ (square numbers) divided 1 - 100, numbered 1, 2, 3...1[0], 12, 2[0], 3[0]...100; 1 - 3 subdivided to 0.02; 3 - 10 subdivided to 0.05; 10 - 30 subdivided to 0.4; 30 - 50 subdivided to 0.5; 50 - 70 subdivided to 1; 70 - 100 subdivided to 2.
3. ‘S |CS|SEC’ (sines, cosines (?) and secants) divided left to right [40´] - 90˚, numbered 1, 2, 3...10, 20, 30...90 and right to left [0] - [89˚ 20´], numbered by 10˚; scales share divisions, which for left to right scale are: 40´ - 10˚ subdivided to 10´; 10˚ - 30˚ subdivided to 15´; 30˚ - 60˚ subdivided to 1˚; 60˚ - 80˚ subdivided to 2˚; 80˚ - 90˚ subdivided to 5˚.
4. ‘Ver. sines’ divided [0] - [168˚], numbered by 10˚ (and for 165˚); 10˚ - 50˚ subdivided to 2˚; 50˚ - 90˚ subdivided to 1˚; 90˚ onwards subdivided to 30´.
5. ‘Tangent’ divided [40´] - 45˚ and back to [89˚ 20´], numbered 1, 2, 3...10, 20, 30, 40, 45, 50, 60, 70, 80; 40´ - 10˚ subdivided to 10´; remainder subdivided to 15´.
6. ‘Meridian’ divided [0] - 60˚, numbered by 1˚, subdivided to 20´.
7. ‘Mer Continued’ divided [60] - 80˚, numbered by 1˚, subdivided to 10´.
8. ‘Num. Root’ (square roots) divided 1 - 10, numbered by 1; 1 - 2 subdivided to 0.02; 2 - 3 subdivided to 0.04; 3 - 10 subdivided to 0.1.
9. ‘Num. cube’ divided 1 - 1000, numbered 1, 2, 3...10, 2[0],...100, 2[00]...1000; 1 - 2 subdivided to 0.02; 2 - 3 subdivided to 0.05; 3 - 5 subdivided to 0.1; 5 - 10 subdivided to 0.1; 10 - 20 subdivided to 0.2; 20 - 30 subdivided to 0.5; 30 - 100 subdivided to 1; 100 - 200 subdivided to 2; 200 - 300 subdivided to 5; 300 - 1000 subdivided to 10.
10. ‘Eql Deg’ divided 0 - 10˚, subdivided to 10´.
List of relationships for navigational calculations at left hand end of reverse: ‘R : DIST: : SC: DP :: SCC : D LAT’, ‘D LAT : DEP :: TAN : 45 : T COURSE’, ‘SC MID : LAT : DP :: R : D LONG’, ‘D LAT : DEP :: MD LAT : D LONG’, ‘SC L : SO DEC :: R : SO AMP’.
Brass pins.

Condition good; complete.

References

Events