Signedin ink on box label: W. A. Rogers.
printed on slide label: W, A. ROGERS, / CAMBRIDGE, MASS.
Inscribedprinted on slide label: Stage Micrometer,
in ink on slide label: R.C.G. / 1000 / 2000 / 5000 / 10000 / 20000 / 30000 / 40000 / 50000 / 60000 / 80000 / 96000
on box label: Stage / Micrometer
on box label: R. C. G.
FunctionSometimes called a stage micrometer, this microscope slide is ruled with very fine lines. It serves as a test plate for the resolving powers of a microscope and is used to calibrate precision measuring instruments.
Historical AttributesIn 1919, Elihu Thomson brought this stage micrometer by W. A. Rogers to Dr. Harold Ernst and left it as a gift. Dr. Ernst recorded: "A stage micrometer ruled by W. A. Rogers of Cambridge [received as a gift] from Elihu Thomson, 1919." Later Dr. Ernst added: "A good specimen of the work of this individual and in good condition (March 1921)."
In January 1920, a note from Elihu Thomson to Dr. Ernst conveyed his excitement over graticules like Rogers, this time from the perspective of a microscopist. Thomson made reference to Robert B. Tolles microscope objectives and their remarkable resolving power. Thomson had borrowed a "splendid 1/7 Tolles" and returned it with a box he had made for it. He remarked, "I think I will have to try to rule 150,000."
Inspired, Thomson went on to make his own rulings, three of which he showed off and presented to Dr. Ernst a week later in January 1920. In February 1920, Thomson added a fourth slide divided to 1/136,000 of an inch.
The Elihu Thomson letters are currently in the Tolles-Dalton papers (2008-1-0079)
Correspondence between Dr. Frederic Lewis and Dr. S. Burt Wolbach about the Rogers and Thomson stage micrometers are in the files for 1091b.