An English compound microscope, unsigned, probably made by Andrew Ross, circa 1835

Details
An English compound microscope, unsigned, probably made by Andrew Ross, circa 1835

The flat tripod foot has extensions to the feet so that when folded back stowage in the fitted mahogany case is easier. A vertical pillar is screwed to the foot, and thhe limb is attached at the top through a universal ball joint, with a tightening key. The ball is part of the stage plate, through which runs a tube containing the coarse focusing rack to the horizontal bar to which the body tube is fixed. The fine focus control is from a knurled wheel at the bottom of the limb. Under the extension to the stage plate is a thick collar with diagonal X - Y movements by knurled wheels. Into this collar screws a short tube that supports the specimen stage, with clips and two holes for accessories such as stage forceps. The stage plate has a single hole to take a bracket holding a small bull's-eye lens via two rods. Below the plate, the limb carries two collars for the concave mirror and a condensing lens. Both of these items are on pegs for ease of removal when a tube 6in. (15cm.) long can be screwed into place. This tube contains a small plane mirror and an adjustable condenser lens.

The optical tube is fixed in its bracket, which can be removed so that a split-ring holder for simple objectives can be brought over the optic axis. Two eyepieces are present. A single button objective is attached to the nosepiece of the body tube, while a lower power (10x) objective has a lieberkuhn in a sliding tube. There are two simple lenses in brass mounts that fit into the split-ring mount at the top of the pillar.

Also present are a brass live box, stage forceps, a split-ring mount on a peg and a double convex lens in a brass cell. All can be packed into a mahogany box with blue velvet on the supports, and a small box is provided for the objectives. All contained in a fitted mahogany case 11.1/2in. (29cm.) wide

See Colour Plate 15

Lot Essay

The Maker
A design of microscope with some features similar to those described above, notably the universal ball joint at the top of the pillar, is illustrated in an engraving dated 1 May 1829 and published in C.R. Goring and Andrew Pritchard, Microscopic Illustrations (London, 1830). The instrument is entitled: "Goring's Operative Aplanatic Engiscope"; but no maker is mentioned. A microscope also similar to the above, but actually signed: "Ross London" is shown in A.D. Morrison-Low and R.H. Nuttall, Ross Microscopes as used by David Brewster and Richard Owen", Microscopy, 3 (1982), 335-344. The authors refer to three instruments of this type. Recently, another similar instrument, also signed "Ross London", is fully described by M.E. Rudd and D.H. Jaecks, The Rapid Development of the Achromatic Microscope: An Early Example by Andrew Ross", Bulletin of the Scientific Instrument Society, No. 49 (1996), 17-21. The present example is, therefore, the fifth known, and through certian intercomparisons it seems to be the earliest in the group.
Andrew Ross (1798-1859) was working in Clerkenwell from 1831. From about 1837 he was making objectives to the design of J.J. Lister, and to show the collaboration he named his firm: "Andrew Ross & Co.", with premises in Picadilly from 1839. Thus one may assume that this microscope was made between 1831 and 1839, and possibly in about 1835.

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