Historical information

Speculum metal blanks made by John H. Brashear(1840-1920) from John Hopkins University in Baltimore, Diffraction Grating made by Prof. H.A. Rowland, [School of Physics, University of Melbourne.] No known publications using the Eagle mounting. May have been used exclusively for practical work in Physics III.

Physical description

Diffraction grating of 14,437 lines/inch x 3 1/4 inch. Set in goniometer. “The grating is a ruling of 14,437 lines/inch by Rowland, on a concave spherical speculum mirror of 4-1/2 inch aperture and 10 ft radius. First order dispersion is 5.5 A per mm.” (see RTW Bigham: ‘Concave Roland Grating: Eagle Mounting” in ‘Inspection of New Wing’; Appendix B5 , Vol 2 of Laby :CollectedPapers. The remnants of the Eagle Mounting, featuring a 4 inch tube x 10 ft long, presently uncatalogued, lies on the roof of a display cabinet in the PSB basement open cage-store.

Inscriptions & markings

Kirkpatrick & Co., London