Signedengraved on objective: R. B. TOLLES, / BOSTON.
scratched on mount: 73 x 6 x 30
Inscribedengraved on objective and on canister: 1/75 / Immersion.
Historical AttributesIn its day, this objective was the highest power ever made, and was justly famous. Tolles made this objective at the request of Dr. A. G. Harriman of Boston, the discoverer of nerve fibers in the soft solid matter of dentine.
The lens had a working distance of 1/250 of an inch and it cost $400. It had an angular aperture of 173° - 178°. The posterior pair of lenses were adjustable to the cover slip thickness. Dr. Harriman used glass cover slips that were 1/250 of an inch in thickness.
According to a report delivered by Charles West to the American Society of Microscopists in 1886, the lens was available for photographic purposes and when properly illuminated gave a "moderately clear definition" with eyepieces B or lower. The apparent size of a blood corpuscle viewed through it was "that of a ten cent piece, so that its magnifying power, without amplifier, is not far from 7,500 diameters."
Tolles never made another 1/75 objective.
By 1886, this instrument was owned by Dr. Ephraim Cutter of New York. Cutter was a big fan of Tolles. At his death in 1917, some of his instruments and papers were incorporated into the Ernst-Lewis Collection at the Harvard Medical School.
Primary Sources"Tolles' Triplets," American Naturalist, 7 (1873): 507.
R. B. Tolles, "Note on a New 1/75 Objective," American Naturalist, 7 (1873): 638.
Charles E. West, "Forty Years' Acquaintance with the Microscope and Microscopists," Proceedings of the American Society of Microscopists, 8, Ninth Annual Meeting (1886): 161-173, esp. 173.
Published References"Ephraim Cutter," National Cyclopaedia of American Biography (New York, 1939), 27: 103-104.
Deborah Jean Warner, "The Microscopes and Telescopes of Robert B. Tolles,"
Rittenhouse 9 (1995): 65-83. see 67.