Microscope Museum

Collection of antique microscopes and other scientific instruments

Microscope 509 (Ross; Student’s microscope; 1880s)

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 509 is signed ‘Ross, London’ and has the serial number 5031, being dated to the 1880s. It is an example of the Ross-Zentmayer Student’s microscope (Figure 1), about which the following excerpt was taken from the 1883 Carpenter’s book “The Microscope and Its Revelations”: “Another instrument of superior make … with the view of affording to the student the advantage of the swinging tail-piece for oblique illumination devised by Mr. Zentmayer; … This tail-piece swings round a pivot which serves for the attachment of the stage to the limb; and at the back of the limb is a milled-head working on the projecting end of this pivot, by tightening which the stage may be firmly fixed in its ordinary horizontal position, whilst by loosening it the stage may be made to incline to one side or the other. The tail-piece carries, between the mirror and the stage, a sub-stage, fitting into which may be screwed an ordinary 1 inch, 1 1/2 inch, or 2 inch objective, which answers the purpose of an achromatic condenser; and when a pencil of light reflected from the mirror has been made by it to focus in the object, the swinging of the tail-piece to one side or the other will give any degree of obliquity to the illuminating pencil that may be desired, without throwing its focus off the object, as this lies in the plane of the centre round which it turns. The tail-piece may even be carried round above the stage, so that light of various degrees of obliquity may be concentrated upon opaque objects. … A mechanical stage may be added, if desired. The workmanship of this simple model is of the highest class; and there is little real work, of which, in the hands of an observer who knows how to turn the instrument to the best account, it may not be made capable, by the addition of a Polariscope, Paraboloid, and other accessories, which its sub-stage adapts it to receive”.

Figure 1. Ross (Zentmayer) Student’s microscope as featured in WB Carpenter’s 1883 book entitled “The Microscope and Its Revelations”.