Description

Background to Andrew Ross & Co.

Andrew Ross founded his business in 1830 and, like James Smith, later of Smith & Beck, he collaborated with J.J. Lister, the manufacturing optician 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 other contemporary makers, including a construction style similar to that of the Lister-limb design.  He continued this practice until 1840 when he developed the “bar-limb”, a very stable design and from then on also supported his 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 19th century. Some conservative companies such as Powell and Lealand continued the manufacture of bar-limb microscopes into the 20th century, long after improved continental designs appeared in the market. Andrew Ross died in 1859 and his son Thomas Ross carried on the business. Thomas Ross died about 1870 and the management of the firm was taken over by famous inventor Francis Wenham who was responsible for the development of the Ross-Zentmayer models in the 1880s and these remained in production into the 1890s until replaced by continental designs. The Ross company went on to produce optical products well into the twentieth century, although large high-quality microscopes became less important to the firm as the years went by. The firm was called Ross & Co between 1837 and 1841, then Andrew Ross & Co and finally Ross Limited from 1897 onwards. The firm discontinued the production of microscopes in 1906. (Source: ‘Antique Microscopes’ website)

This example of a Ross binocular microscope presents really well with some lovely gleaming brass-work details and some age-appropriate patination here and there, although nothing detracts from the visual appeal, which is what you’d hope for with an antique instrument of this age.  The instrument’s look and feel is of a quality not found in modern microscopes in that’s it’s fashioned from solid brass, giving it a great stability, solidity and quality feel and it’s also quite a large instrument at around 20 inches in height when inclined for use, rising to over 24 inches when positioned vertically.

Technical details – the construction is a brass A-shaped foot (also sometimes referred to as a Lyre-shaped foot) with large twin uprights supporting a pivot and a Jackson-Lister upper limb arrangement.  The coarse focus is by rack and pinion with the newer-style helical cut that features on instruments from the 1880s onwards and there’s plenty of travel, so I reckon even a 4 inch objective would achieve sharp focus (it does – currently using it with a Watson 4 inch para objective).  The coarse focus has a nice smooth action and holds in position as it should in its working range and there’s tension adjustment available as required.  Fine focus is operated via a graduated brass thumb-wheel located at the rear of the main tube on the limb, being a vernier screw acting on a lever against sprung resistance, also working well.  The lever fine focus is a specific feature of the Ross-Zentmayer and was also adopted by Watson for their Edinburgh series of microscopes.

In terms of its optics, this microscope has a Wenham double optical tube with mechanically operated graduated draw-tubes with nice smooth action.  The Wenham prism is present in its carrier in clean condition, rendering good usable images.  It’s supplied with a good number of top-hat eyepieces that with correct illumination produce bright age-appropriate images, as under:

Eyepieces for binocular use:
– A with specific Left & Right – 5x magnification 
– B – 6x magnification
– D – 10x magnification

Eyepieces for monocular use – right-hand eyepiece tube only:
– C – 8x magnification
– E – 12x magnification
– F – 15x magnification

It’s also supplied with a number of good period objectives and has the advantage of being RMS.  The objectives are all originals by Ross in good condition and all fitted with correction collars except for the 1 inch, as follows:

– 1 inch – approx 6x magnification
– 1/2 inch – approx 12x magnification
– 1/4 inch x 2 – approx 25x magnification
– 1/10th inch – approx 75x magnification
– 1/15th inch – approx 125x magnification

In addition there’s  a low-power Watson 4 inch objective which is about 2x magnification with very high working distance and this is shown fitted in the listing photos along with a nicol prism analyser.

I’ve tested the optics with various antique slides and also thin-section mineral and crystal specimens and the images are perfectly acceptable when using good illumination – in fact this is one of the best Wenham binocular set-ups that I’ve known, with nice sharp bright images in both eyepieces, with as often the case with antique Wenham optics slightly lower light intensity to the left-hand eyepiece.  It’s also of interest to the reader that Francis Wenham was working at Ross when this instrument was manufactured, so it’s likely that he was closely involved in its manufacture,  Also of interest to the collector is the pattern of the Wenham prism in this example, which is slightly different to the norm and apparently Wenham designed something like 17 different prism patterns, with this no doubt being one such example. The magnification available with the instrument with its current set of optics will be around 10x to a theoretical figure that’s in excess of 1,000x.

The instrument tilts for inclined viewing and holds in position as it should on inclination and can be tightened via a limb-tension lever to the right hand side of the pivot.  The all-brass specimen stage is fully mechanical with in addition a mechanically operated rotation feature with rotation controlled via a sub-stage thumb-wheel – note it’s not full 360 degree rotation.  The x/y adjustment thumb-wheels are on the right-hand side, giving about 1 inch of travel in the x/y planes, with the rotation control below stage.  All the mechanical controls work very well and hold position on inclination, with rotation well damped – there’s also a silvered 360 degree scale on the outer edge of the stage.  The stage top-plate has a rest for holding slides and two dovetail sliders that can be adjusted to hold the slide firmly in place, both moving freely.  

Turning to the sub-stage, the first thing to note is that this instrument has a swinging sub-stage, a degree scale for setting the sub-stage angle and a set-screw for locking in vertical position.  Swinging sub-stages were a development introduced in the 1880s to assist with inter alia oblique specimen lighting and although popular at the time, this feature was largely phased out by the 1890s once better Abbe-type condensers became more widely available.  

Sub-stage on the tail-piece we have a dovetail recess where Ross-Zentmayer specific sub-stage accessories are fitted – such as various types of condensers, polarising hardware etc.. as supplied and listed below under the section on Accessories.  Lighting is via an over-size plano-concave mirror in a brass gimbal mount with swing, rotation and height adjustment, with silvering showing some characterful aging to both sides and still perfectly functional.  

Accessories:
– dovetail-fit accessory holder with rack & pinion height adjustment, centering and 360 degree rotation
– sub-stage Abbe-type condenser assembly with horizontal rack & pinion centering, swing-out feature and two fixed stops
– darkground condenser
– nicol prism sub-stage polariser together with three integral swing-out rotating selenites – 1/4, 3/4 & 9/4 – producing spectacular colour changes under polarised light conditions
– nicol prism nose-piece analyser with rotation
– lieberkuhn reflector for 1 inch
– lieberkuhn reflector for 1.5 & 2 inch
– side reflector 
– live cell
– image projection device
– some additional accessories as shown

The instrument has been very gently dusted and also lightly lubricated with non-hardening grease where appropriate, so that the controls operate smoothly.  This example displays exceptionally well having a very substantial presence and some lovely brass-work with rich gold and copper tones which catch the light beautifully.  This antique microscope is very much a usable proposition for brightfield, darkfield and polarised light work and as presented includes some superb accessories and of course a correct period storage case with lots of internal racking.  It should make a stunning antique display piece as is, perhaps in a library or home office type of setting, especially when set up with an appropriate antique slide.  

Owing to the weight and delicacy of this antique microscope, it will be partially dismantled, carefully wrapped for shipping and dispatched by insured courier upon receipt of cleared funds – it may even require shipping in two packages in view of its size and all the accessories. 

Thanks for looking.