SOME COMMENTS ON INSTRUMENTS MADE BY J.B.DANCER, MANCHSTER, ENGLAND
My interest in Dancer instruments stems from my early life in the design and development of scientific instruments. Whereas Dancer was working at the peak of optical instrument development in the second half of the 19th century, I was privileged to be treading a similar path a hundred years later in the age of the silicon chip development. Although I cannot claim any inventions or discoveries, my work as an electronics design engineer exposed me to the delights of seeing my new designs in production as well as the heartache when, despite long hours of unpaid experimentation, an idea failed to match up to expectations. I should also point out that Dancer's many elegant solutions to the various problems encountered over the years, reinforce one of my very first lessons in design. "The best solutions are always the simplest" That certainly seems to have been the case with Dancers instruments (How far apart should the lenses on a stereoscopic camera be? The same distance as a normal pair of eyes of course.).
This together with a very close geographical link (I was born only a few hundred yards from Cross St.in Manchester, where he worked some 100 years before I was born) has prompted me to record my observations on the Dancer instruments that I have had the privilege to own.
So far, I have collected MICROSCOPES, TELESCOPES, BAROMETERS, DRAWING INSTRUMENTS & PHOTOGRAPHIC APARATUS
IS THIS HOW J.B.D. SAW HIS INSTRUMENTS?
Over the past few years I have been able to study, at close quarters, several of Dancer's low cost microscopes. All of them have been signed on the foot with the now famous signature J.B.Dancer Optician Manchester but the basic instrument (and its case) has developed through several stages to the comprehensive binocular or set which any collector would be proud to have.
The earliest Dancer made (?) microscope I have owned is this one signed by both Abrahams and Dancer when in partnership at 13 Cross St., Manchester (1841 – 1845). This microscope which stands about 13 ½ inches high, is typical of the earlier microscopes made prior to the popularity of the bar-limb designs and was made to be broken down to fit into the flat case popular from the middle of the 18th century. The finishes are yellow brass lacquer and the bronze finish typifying Dancer’s accessories over the years to come. As with many sets made during the early part of the 19th century, this set includes a “Bonanni” type stage which has a bayonet fitting into the top of the microscope stage, wheel of stops condenser which screws onto the underside of the stage, single sided convex mirror, a circular live box & stage mounted bullseye condenser. Course focussing is by thumbwheel rack & pinion moving the stage up and down the main pillar and fine focus by thumbwheel screw at the top of the pillar moving the limb which holds the body tube. The pillar is screwed into the foot and also has a compass joint at the base, for inclining the microscope. Objectives are early “button” types mounted on pre-RMS bases to screw into the body tube which has an external thread to screw into the limb mounted on the main pillar. The objectives are screwed into the cap of the brass can in which they are stored. 2 different power objectives are present along with 2 different power oculars, one stored in the corresponding socket in the case and the other in the body tube. The flat “Y” shaped foot is engraved “Abraham & Dancer, Manchester”. The trade label on the underside of the case lid, whilst being very similar to Abraham’s label, is typical Dancer with the exception that it also has Abrahams name as well as Dancer’s. There are 2 lidded compartments in the main case. One is a multiple accessory compartment and the other is a complicated little case for holding samples. The main case which measures 10 x 8 ¼ x 3 inches is made from fine polished mahogany with brass hinges and escutcheon for the lock key, but the lock & key are missing. There is also a space in the top of the case lid where a brass name plaque once resided.
The first Dancer microscope I owned was of a good size in a mahogany case with a drawer full of accessories.
Whilst the instrument was similar in size to later instruments and had the signed "Y" shaped foot and twin pillar support, the main focus employed the (earlier) Martin or Drum type microscope rack & pinion focussing internal to the main body of the instrument. This used only one control knob on the side of the microscope and when the internal rack had become a little stiff to move, damage to the rack was inevitable.
The case was of the usual high quality polished mahogany with substantial lacquered brass handle and held the microscope and free-standing bullseye condenser in the manner Dancer seemed to favour for the majority of his microscopes.
The accessory case, however, I have only seen in his early (1840's & 1850's) microscopes. This is a single large drawer with lid mounted on it's side in the main case, similar the style used by Powel & Leyland and Smith & Beck on their most expensive microscopes. In this single accessory case was fitted a stage bullseye condenser, ivory or bone handled spike & scalpel, tweezers, a live box, stage forceps, 4 objectives (one with Lieberkuhn) all of the pre-RMS thread sizes, a quantity of slides and a polariser & analyser set. This accessory set seems to have employed a particularly neat yet simple storage method using an external thread on the end of the analyser tube to fix it to a matching internal thread in the polariser. This saves the necessity for 2 end caps to keep the dust out of the Nicol prisms, The analyser screws into the top of an objective before attaching to the microscope. The poleriser slots under the stage on a dovetailed carrier.
The trade label on the inside of the case door has the address as being 13 Cross St., which I would date between 1841 & 1846. However, I understand Dancer was in partnership with Abrahams form 1841 to 1845, so perhaps this was one of the very first microscopes Dancer made after the partnership broke up, dating it to 1846. This is how 13 Cross St. looks today.
Early Large Best Microscopes
This large “best” microscope is from a similar date to the one above but has all the looks of a top of the range instrument. The twin handled polished mahogany cabinet holds all the accessories in 2 polished mahogany fitted drawers with ebony button knobs. These include a watchmakers eyeglass, polariser/analyser, one top hat style wide lens eyepiece, camera lucida, fishplate, large overstage, small overstage, 1/8, ½ & 2 inch objectives in matching lacquered brass cans, live box, compressor stage, wheel of stops, forceps, stage forceps, dark well, illuminator, micrometer & spanner. A further 7 drawers are provided for slides and storage of other small items. The rectangular section limb has a swivel joint to allow the optical tube to be set outside the area of the stage. Main focus is by rack & pinion using twin wheels, fine focus is nose-mounted lever type and the draw tube is engraved to facilitate setting the tube length for each objective. The instrument has accessories for both over and under the mechanical stage. Concentric shafts drive the “Y – Y” movement of the stage by rotating thumbwheels, the fore/aft drive by both left and right hand knobs. The bayonet mounted mechanical sub-stage has an achromatic ”illuminator”. All the objectives are pre-RMS and the 1/2 inch has a built-on lieberkuhn. The plano-concave mirror assembly clamps onto the sub-stage tube with a knurled thumbscrew. The polariser is bayonet fitted below the stage and the analyser screws into the bottom of the draw tube. The fine camera lucida is a tiny speculum mirror on an arm mounted from the eyepiece and fitted into it’s own lacquered brass can for storage. The microscope is signed on the foot Dancer Manchester. The trade label on the inside of the case door has the address as being 13 Cross St., which I would date to 1846.
The next development I had was a similar style of microscope but housed in the multi-drawer case. This seemed to be the next phase in case development as small blind holes had been let into the back of the case door to accommodate the drawer (ebony?) knobs in a very snug fit. The trade label, now at 43 Cross Street, also had to be moved to the inside left panel of the case to accommodate these holes. Later cases had relatively shorter drawers obviating the need for the holes in the door. 43 Cross St. in 2001. I wonder which (if either) of these buildings was Dancer’s premises?
The objectives still had pre-RMS size threads and all the accessories found in the single drawer on previous models were available and fitted in the larger drawers of this case. The other, smaller drawers were mostly fitted out to hold slides on end.
It is also interesting to note the workmanship, which must have been invested in Dancer's free-standing bullseye condenser which came with this set. It was a substantial piece. The three-dimensional adjustment was clamped with thumbscrews and the size was in good proportion to the microscope it was to be used with.
Another, similar microscope of about the same era came in an identical case except for the absence of the blind holes to accommodate drawer knobs. The drawers on this model were short enough not to interfere with case door. This case had also seen better days.
The microscope was similar to the previously described two with the notable exception of the mechanical stage.
The development of binocular or stereo vision through a microscope was tackled in various ways. The most famous of these being the Wenham prism, almost universally adopted for half a century. Other attempts were made, including a three part prism assembly by Dancer. Compare this with the Wenham prism here.
Whereas the Wenham method used a beam splitting prism to allow binocular vision through a second eye tube “grafted” onto the side of a monocular microscope body tube, the Dancer method utilised two body tubes in a true “V” format. Each eyepiece receives the same amount of light from the objective. The Dancer binocular prism method was registered No 4380 June 27th 1861.
This particular microscope came to me without case or accessories. It is a large stand at about 18 inches high in use, with the Dancer signature on the heel of the foot. The main focus is rack & pinion and fine focus by thumbwheel operated nosepiece lever. Inter-ocular separation is by rack & pinion driven by a thumbwheel either side of the body tubes. The mechanical stage has a rack & pinion with thumbwheel both sides for fore & aft movement and a single side worm driven lateral control. There is a female bayonet fitting for sub-stage accessories but no accessories present.
The classical twin pillars support the assembly above the Dancer tri-form base. Unusually the base has an arc of heavy brass connecting the front two “toes”. Perhaps this stand began life as a monocular and had to have the extra weight added to the front of the base for balance when the heavier binocular tubes were fitted.
THE MANCHESTER FIELD NATURALIST’S BINOCULAR MICROSCOPE
“Manufactured by the desire of the Committee of the Society” according to Dancer’s 1873 catalogue. The “society” is now the Manchester Microscopical Society (of which I am a member) and can be found at Manchester microscopical
The microscope is a portable Wenham binocular instrument which disassembles to fit into it’s case. It is built on the Ross bar limb style with the Wenham prism mounted in a shoe to slide into the body tube. With the prism in line with the optical axis the microscope works as a low power binocular and with the prism out of the optical axis the microscope is a monocular capable of high power magnification. The microscope takes the RMS standard objectives and has lots of unusual features. Apparently it was offered with either rack & pinion main focus or chain drive. This is chain driven, presumably to reduce weight. Inter-ocular separation is by a simple (lightweight) lever mechanism, and the plain stage has a slide bar. The stage has a central hole threaded to take sub-stage accessories. Below the stage is a plano-concave mirror. The microscope is signed on the foot “J.B.Dancer Manchester” and is numbered “26”. Whilst the inside of the case and drawers are fitted out to take a host of accessories, sadly the only remaining are a higher power eyepiece and a nosepiece analyser.
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