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Ross Zentmayer Grand Monocular
[Photographs by Matt Nunn.]
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20074
A Ross Zentmayer No. 1 Grand Monocular Microscope:
English/American ca. 1885. SN 5389. This Andrew Ross microscope is fitted with Joseph Zentmayer's swinging substage. Hence the designation as a Ross Zentmayer microscope. The microscope itself seems to have multiple collaborative elements from both workshops however. The microscope is of lacquered brass and stands 19 in. tall when fully racked down to its minimum focal length. The microscope is fitted with a lyre shaped foot, and a mechanical stage (X & Y, both by rack and pinion control).
Historical:
"Ross London" refers to Andrew Ross (1798-1859) was a well known and successful scientific instrument maker working in London in the 19th century (1,2). He was apprenticed to John Corless in the Joiners' Company in 1813 and eventually became an optician, starting his own business in 1830. He collaborated with J.J. Lister from 1837-1841 and introduced a number of improvements to microscope design. He became one of the best microscope manufacturers in London. Ross's optical firm was well know for producing quality lens and achromatic objectives for microscopes. One of his microscope models won 1st place at the Great Exhibition of 1851. Ross only started to introduce serial numbers to his instruments in August 1842, so early instruments with Ross's signature, but without a serial number, can tentatively be dated to pre-1842.
Andrew Ross's optical business was first located at 15 St. Johns Square, London (1830-1839). He then relocated to 33 Regent St. Piccadilly (1839-1843). In 1843-1859 he was located in several units of the Featherstone Buildings in Clerkenwell. When he died in 1859, the business was taken over by his son Thomas, and was re-named Ross & Co. The firm eventually moved to 112 New Bond Street (1880-1893).
Joseph Zentmayer (1826-1888) was a German-American maker of microscopes and other optical instruments (3,4). After his apprenticeship in Germany, he immigrated to the US in 1848 and set up an optical workshop in Philadelphia in 1853. He is well known for his American Centennial model which was patented in 1876. He was awarded a medal at the Centennial Exposition of 1876 for this microscope for innovation and craftsmanship. His microscope inherited the name of the exposition, i.e. "Centennial" since it was first introduced and featured at this event.
Joseph Zentmayer's articulating substage assembly was an excellent improvement. The axis of rotation of the assembly was designed to be in the same plane as the specimen, at all times, which allowed the focus of the condenser to be maintained regardless of the angle chosen. This gave correct illumination above, below, or from the side of the stage.
Bibliography:
1. Clifton, G. (1995) Directory of British Scientific Instrument Makers 1550-1851 ISBN [0 302 00634 6] p.238.
2. Online resources:
a.) [www.vayafigara.files.wordpress.com/2010/02/ross-1930-1945.pdf].
3. Proceedings of The American Microscopical Society (1893) Vol 4; No. 3; p. 161-166.
4. Online resources: a.) [www.en.wikipedia.org/wiki/Joseph_Zentmayer]. b.) [antique-microscopes.com/photos/zentmayer_american_centennial_microscope.htm].
4. Online resources: a.) [www.en.wikipedia.org/wiki/Joseph_Zentmayer]. b.) [antique-microscopes.com/photos/zentmayer_american_centennial_microscope.htm].