Microscope Museum

Collection of antique microscopes and other scientific instruments

Microscope 528 (Ross; Ross-Zentmayer student’s microscope; c. 1880)

Andrew Ross founded his business in 1830 and, like James Smith, collaborated with J.J. Lister, the maker who invented a mathematical method of producing objectives which were both achromatic and aplanatic. Ross's early instruments were constructed initially in a fashion similar to the Jones-most-improved models, followed by a construction similar to that of the 'Lister Limb' and he continued this practice until the 1840's when he developed his version of the Bar-Limb, a very stable design and from then on also supported his larger stands on the classic Y-shaped foot with two upright supports. Early examples of the Ross Bar-limb construction used a triangular bar, which was later replaced by a square one and finally on the largest and heaviest version, a rectangular one. The Ross Bar-limb design became the standard for many British microscope makers throughout the second half of the 19^th century. Some conservative companies such as Powell and Lealand continued the manufacture of bar-limb microscopes into the 20^th century, long after the improved continental design. Andrew Ross died in 1859 and his son Thomas Ross carried on the business. Thomas Ross died about 1870 and Francis Wenham took over the company. Among his inventions was the Wenham binocular tube. At some point, Francis started using swinging substages and long-lever fine focus on his microscopes, which were both innovations of the American microscope manufacturer Joseph Zentmayer. Wenham started making the famous Ross-Zentmayer microscopes and these dominated the 1885 catalogue of Ross microscopes. These microscopes were available in at least four different sizes, most as monocular or binocular, and microscope 509 is an example of such Ross-Zentmayer microscopes. The Ross company went on to produce optical products well into the twentieth century, although large high-quality microscopes became less important as the years went by. The firm was called Ross & Co between 1837 and 1841, and Ross Limited from 1897. The firm discontinued the production of microscopes in 1906.

Microscope 528 is signed ‘Ross, London’ and has the serial number 5221, being dated to c. 1880. It is an example of the Ross-Zentmayer Student’s microscope (Figure 1), about which the following excerpt was taken from the 1883 Jabez Hogg’s book “The microscope, its history, construction and application”: “The Ross-Zentmayer Student’s Stand … is a useful instrument on a small scale, possessing all the advantages of a larger microscope. It has an excellent fine adjustment, the milled-head for working which is in as convenient a place as that of more expensive stands. It is not so costly as more pretentious instruments, a consideration often of importance to the student of the collateral sciences. Messrs. Ross make a very good and cheap series of object-glasses for histological work, especially adapted for use with this instrument”. This microscope was offered in two forms, one with coarse focus using a rack and pinion mechanism (Figure 1), and a less expensive version with sliding coarse focus (like microscope 528).

Figure 1. Ross (Zentmayer) Student’s microscope as featured in the 1883, 1886 and 1890 editions of Jabez Hogg’s book “The microscope, its history, construction and application”.