Accession No

2951

Brief Description

diffraction grating, reflecting, Rowland-type, by John A. Brashear, U.S.A., 1888

Origin

U.S.A.; Massachussetts; Baltimore; and U.S.A.; Pennsylvania; Allegheny

Maker

Brashear, John A. [polished and figured] Theodore C. Schneider [ruled using Rowland's engine]

Class

optical

Earliest Date

1888

Latest Date

1888

Inscription Date

1888

Material

metal (speculum metal; brass); wood

Dimensions

plate 161mm x 135mm; ruled surface 146mm x 50mm box length 197mm; breadth 179mm; height 115mm

Special Collection

Provenance

Transferred from Department of Physical Chemistry, University of Cambridge, Cambridge, England, 03/1983.

Inscription

‘Ruled on Prof. H.A. Rowlands Engine 1888
John Hopkins University Baltimore Md USA
Radius of curvature 21 feet + 10,000 lines to in’ (scratched on surface)
‘Plate Polished and Corrected at the Astronomical
and Physical Instrument Works of
John A. Brashear Allegheny Pa U.S.A.’

Description Notes

Diffraction grating, reflecting, Rowland-type, by J. A. Brashear, U.S.A., 1888.

Rectangular speculum metal plate with raised polished platform, containing rectangular ruled surface. Wooden tray with two handles in fitted wooden box. Blank square brass plate.

Manuscript inscription reads:

‘Ruled on Prof. H.A. Rowlands Engine 1888
John Hopkins University Baltimore Md USA
Radius of curvature 21 feet + 10,000 lines to in’ (scratched on surface)
‘Plate Polished and Corrected at the Astronomical
and Physical Instrument Works of
John A. Brashear Allegheny Pa U.S.A.’

Condition

References

Events