Grating, concave

1901

Title
Grating, concave
Collection
Caltech Images Collection
Series
Scientific Instrument Photographs
Identifier
ST-PH-09
Dates
1901
Extents
1 photographs (negative)
Abstract
This grating was ruled on speculum; a light aluminum coat has since been applied. The plate was prepared by the John A. Brashear Co., Allegheny, PA. It was ruled on Prof. Henry Rowland’s engine at Johns Hopkins Univ., Baltimore, MD. Used by Bowen and Millikan from 1919 on.
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