Accession No

1413

Brief Description

chemical balance, 5 1/2-inch beam, by Robinson, English, c. 1835

Origin

38 Devonshire St; Portland Place; London; England

Maker

Robinson, Thomas Charles

Class

balances

Earliest Date

1825

Latest Date

1841

Inscription Date

Material

wood; metal (brass, steel); stone (agate); glass

Dimensions

balance length 270mm; breadth 150mm; height 228mm overall length of beam 154mm; pan diameter 47mm; box breadth 231mm; box depth 105mm

Special Collection

Provenance

Transferred from the Department of Mineralogy and Petrology, University of Cambridge, in 12/1961. Used by W.H. Miller when remaking the standard pound.

Inscription

‘ROBINSON.
38 Devonshire,
Portland Place London.’ (base plate)

Description Notes

Chemical balance, 5 1/2-inch beam, by Robinson, English, c. 1835.

Brass balance. Open triangle shaped beam with steel centre knife and steel end knives with inclined slit and steel pressing screw adjustment. Pointer below centre knife with screw sensitivity bob, turns over silvered scale below. Wire flag adjustment above centre knife. Beam supported on circular brass column screwed to base plate, with two mutually perpendicular bubble levels. Column continues as pierced uprights and diagonal struts to arresting bar and V notches for end knives. Agate centre plane held by two knurled screws, removable to allow beam to be taken off. Central lever-operated arresting mechanism locates beam and end plates by crutch system. Two brass pans with cords hung from brass and steel J wires with agate plates fitted beneath. Lever pivoted pan arrestment on base board. Base board has three brass levelling screw feet and fitted drawer. 100 and 200 grain weights extant and tweezers. Wooden cabinet fits over balance onto base board. Glazed front and rear. Side opening doors. Spare J wire in envelope.

Condition

References

Events

Description
The modern short-beam precision analytical balance is normally considered to have originated in 1866 with the theoretical analysis and practical achievements of the German engineer Paul Bunge. Whilst Bunge was the first to indicate the theoretical possibility of attaining a highly sensitive and stable short-beam balance, a London instrument maker, T.C. Robinson, had attained that end some 40 years earlier. By 1829 Robinson was advertising his 5 1/2inch beam balance was capable of bearing 400 grains in each pan with a sensitivity of .001 grain.

This balance was used by W.H. Miller (Professor of Mineralogy at the University of Cambridge 1832-1880) during the work associated with the preparation of the new Imperial standards of weight consequent on the destruction of the old standards in the burning of the Houses of Parliament in 1834.

The instrument embodies all of the features present in Robinson’s later instruments. The centre bearing is a single agate plane. The J-wires incorporate agate planes.

FM:40651