Description

A one of a kind brass monocular microscope by Andrew Pritchard c. 1835-1838. Pre-serialization and doubly signed (on body tube and  cruciform foot) in flowing script “Andrew Pritchard, 263 Strand, London”, this pre-RMS microscope has taken me 2 years to re-assemble from 2 US locations due to a calamity of misadventures.

3 pre-RMS objectives (1 stacking, 2 in canisters) with estimated focal length-magnification of 1/2, 1/4, 1/6 and 1/8 inches.

Pre-amble Turrell/Varley mechanical stage c.1833 with screwed down 4 inch bevelled edges and sliding stage mount with stage clips. There is a single hole on the leading edge for stage forceps and/or bullseye but unlike later stages by Pritchard, no swinging arm on the underside.

Articulating 2 1/2 inch, double sided mirror on odd rectangular arm with squircle (squared off circular) nuts. Replacement? For the purist, I have another Pritchard mirror with 1/4 circle bracket and 50 % silvering if you wish.

Fully rotatable motion from the upright to the cruciform base with built in height adjustment via a large , triple knurled and locking round nut (flange) at the top of the base stem. When utilised, this microscope can extend to 24 inches in height.

Stable in only one direction when fully inclined horizontally using a Jones-type compass joint. Elegant connection between the bar and the limb (hand shaped and filed triangular hourglass shape).

The limb is fixed by a large screw (not the usual swinging, bi-directional arm seen later for use as a simple? microscope or candle holder. Coarse adjustment by rack and pinion with a triangular rack (perfect) via two massive treble knurled bronze knobs. The entire microscope is a combination of brass and bronze, including the stage which has X-Y motion by worm and screw (somewhat archaic) with one removeable knob for the left-handed microscopist. 

Body tube surmounted by eyepiece protective cap marked 2 with silvered ocular below. Focussing is by either draw tube or a never before seen separate rack and pinion for fine adjustment. This combined with a separate knob just ahead of the large limb screw for fine adjustment to the nosepiece puts this microscope over the top as far as complexity for this era (1835).

The body tube terminates to a pre-RMS, double swinging objective changer (Ross copy). The body tube is 11 inches long with a diameter of 1 1/2 inches. Lacquer coverage is about 50%.

The 4 inch bevelled stage has a sliding carriage with stage clips and a non-threaded substage opening for polarising and light reducing/condensing accessories. So far I have found a bullseye-type condenser (sorting through boxes for the wheel of stops, iris? and Nicol prism-odd diameter). I have a pair of stage forceps and stage bullseye. 

His innovations are elegant, his machining somewhat cumbersome as he was obviously working from publications by Ross, Turrell/Varley, P&L, Jones, etc. This had to have been an experimental/special order microscope. Searching through museum and private collections, I could find NO other Pritchard model with this combination of special features. I have another later model (unsigned ) and retailed by Powell and Lealand in it’s case but the interior has been modified. The cruciform base is symmetrical, no body tube rack and pinion, under stage swing arm for accessories, etc. Knurling (roping) of the brasswork is definitely Pritchard. Pritchard was only at this address for 3 years. Exciting times for this optical pioneer.

Photos to follow. Latter showing the original mirror.