Thornton K285 Mercury 198 Wavelength Comparison Rule

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Country of manufacture: England,            Date of manufacture: ____
Overall length: 49.2 cm,          Total Thickness: 1.7 cm,           Width: 6.6 cm          Weight: 390.4 gms
Materials: Celluloid and mahogany pinned laminate,
Cursor: Two cursors, one on each side, each 6.0 X 7.5 X 0.6 cms; aluminum runners holding plastic lens, adjustable; lines = single line on each of the two cursors
Scales: 14, specialized
Front: (positive shifts side) micron, Cadmium red, Mercury 198 {Yellow 1, Yellow 2, Green Violet}, 1 X 10 ^-6 inch
Back: (negative shifts side) micron, Cadmium red, Mercury 198 {Yellow 1, Yellow 2, Green Violet}, 1 X 10 ^-6 inch
Gauge Marks: [       ]
Condition: C4 (minimal signs of use),            Came with: Original dark green cardboard case/box
Note: This is, of course, not a slide rule. It seems to be a table look-up tool used in spectroscopy to allow the determination/prediction of the shifts in specific ¹⁹⁸Hg lines based upon the observed shifts of other ¹⁹⁸Hg lines. If anyone out there has any other information about this tool or its use, I'd definitely be interested in learning about it.

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