Accession No

1645

Brief Description

humidity slide rule, by A. G. Thornton Ltd., English, c.1930

Origin

England; Manchester

Maker

A. G. Thornton Ltd.

Class

calculating; meteorology

Earliest Date

1930

Latest Date

1930

Inscription Date

Material

wood (plywood); plastic (celluloid, perspex), metal; paper (card); hide (leather)

Dimensions

length 286mm; breadth 47mm; thickness 17mm case length 320mm; breadth 49mm; height 21mm

Special Collection

Provenance

Donated in 05/1973.

Inscription

‘A.G.THORNTON LTD Mk II BILHAM HUMIDITY SLIDE RULE (FOR TEMPERATE LATITUDES) M 279/42/45’ (stock on obverse)

Description Notes

Plywood core with celluloid scales.
Lower part of stock carries three scales: first marked 1 and ‘wet bulb & dew point’, divided [5˚] - 80˚, numbered 10, 20, 30, 35, 40...80. Second marked 1a, divided [5˚] - [32˚], numbered by 10˚. Third marked 2 and ‘vapour pressure’ divided 1 - 34, numbered by 1, subdivided to 0.1.
Upper part of stock carries double radius log scale marked 5, dividd 1 - 100, numbered 1, 2...10, 20...100.
Slide carries four scales: first marked 3 and ‘depression of wet bulb’, divided [0] - 40˚, numbered by 10˚, subdivided to 0.5˚. Second marked 3a and ‘wet bulb below 32˚F’, divided [0] - 10˚, subdivided to 0.5˚. Third marked ‘4’ and ‘dry bulb’, divided 10˚ - 110˚, numbered by 10˚, subdivided to 0.5˚. Fourth marked 6 and ‘for moisture content’, divided [10] - 140˚, numbered by 20˚, subdivided to 10˚. Two arrows on slide to mark ‘M.C.’ and ‘R.H.’.
Reverse of slide carries four further scales: first marked 3b and ‘depression of wet bulb (aspirated psychrometer)’, divided [0] - 50˚, numbered 5, 10, 20, 30, 40, 50, subdivided to 0.5˚. Second marked 3c and ‘depression of wet bulb (aspirated psychrometer) wet bulb below 32˚C’, divided [0] - 10˚, numbered by 5˚, subdivided to 0.5˚. Third scale marked 4 and ‘dry bulb’, divided 10˚ - 110˚, numbered by 10˚, subdivided to 0.5˚. Fourth scale marked 6 and ‘for moisture content’, divided [10] - 140˚, numbered by 20˚, subdivided to 10˚. Two arrows as before.
Reverse of rule is plain. Perspex cursor is a replacement.
Card slip case covered in green leather.

Condition good; complete.

References

Events