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Microscope by Gardiner (Bristol) c.a. 1863-67




Microscope by Gardiner (Bristol) c.a. 1863-67. Notice the foot mounted in the "inward" orientation and the live box in front of the instrument

This is a third class instrument, according to the classification given by W. B. Carpenter in his reference book "The Microscope and its Revelations" (Churchill, London, 5th ed. 1875), meaning that it has been produced for amateurs' or students' use. From a general structural point of view, this compound microscope is a bar-limb or "Ross" model (introduced for the first time by Ross in 1843), in the simpler form devised by Robert Field in 1855 and known as the "Society of Arts" bar-limb model (with the main tube detachable from the limb by unscrewing it, for easier storage). There are, however, some notable exceptions:


The design of the base is peculiar. The main body rests on a movable plate with two V side arms. This plate can be removed and mounted with the lateral arms in two opposite orientations: the "inward" gives a unique W-shaped or "chickenfoot" base. When mounted with the "outward" opposite orientation the base resembles the more classic Ross Y-foot. Presumably, the "inward" position, giving a lesser encumbrance, can be used for easier storage, while the opposite orientation, in reason of the higher stability given to the instrument, may be ideal when the instrument is set up for use. This may be regarded as a very unusual example of a "folding" foot.

 




Details of the detachable foot mounted in the outward position

 

2) The Huygenian eyepiece is not removable and has been constructed with a peculiar design. In fact, the two plano-concave lenses of the ocular are not part of the barrel body of the eyepiece, as usual, but are mounted separately: the eye lens is inserted in the top-hat element screwed on top of the barrel, while the field lens is permanently mounted inside the barrel itself. This design was typical of old compound microscopes, but it was very uncommon in instruments produced after the 1830's. So, this instrument reflects a quite simple craftsmanship of the manufacturer and an "old" way of conceiving the optical parts of the microscope. The distance between the eye lens and the field lens is c.a. 32 mm, corresponding to c.a. 4X magnification power.

It would be possible, in principle, to obtain a different range of magnification by replacing the top element containing the eye lens with the one of another ocular. I experimented successfully this method with the eye lens of a top-hat 8X ocular of comparable age (c.a. 1880), almost doubling the magnification power of the objectives.

 

3) The mirror is mounted on a bar orthogonal to the plane of the stage and screwed under the stage. This is again different from the vast majority of bar-limb models, where the mirror is usually attached to the main bar carrying the rack and pinion mechanism for the coarse focusing. A similar uncommon design (i.e. one separate bar for the mirror) can be found in a microscope by T.D. King and on an early model by Husbands & Clarke. The Billings Microscope Collection shows only one example of a similar arrangement in an early model by Ross. Thus, this uncommon design has been probably experimented in early models but has been later abandoned, probably because it limits the movements of the mirror. It is not known who was the first to introduce it. The model by Ross predates the one by T.D. King, but too few specimens are known by the latter to be able to make an attribution.

 

4) No fine focusing is present (it is actually unnecessary due to the low magnification power of the instrument).

 

5) The objective thread (female) is not yet the RMS standard one (male), which was introduced in 1858 but took time to be universally used.

 

A barrel is screwed under the stage holding a rotating wheel with three different apertures to regulate the amount of light. No condenser lens is present. The microscope comes with two unmarked multiple-lenses composite objectives, giving an approximate range of magnifications from c.a. 40X - 60X (with the lowest power) and 80X - 120X (with the highest power), as empirically determined by visual comparison of the same objects observed with another microscope at known magnifications.

 


 

As for the overall conditions, they are fair to good.

The optics are still excellent, with no sign of hazing, mold or scratches and giving sharp clear images, as can be seen from the snapshot of a slide of a section of Acacia's stem, taken from my collection of antique microscope slides, as seen through the microscope.

 




Acacia stem, double staining (Hornell Biol. Station, Jersey c.a. 1901) seen with the microscope at approx. 50X (picture taken with a Canon digital camera).

The coarse focusing is a bit slack, due to loss of tight connection between the rack and pinion, so that the focus position has to be manually held all times. But the mechanism is still capable to attain precise focusing also at the highest magnification. All the other mechanical parts are in order. Original lacquer is mostly lost and there are some signs of wear and spots on the tube and base, according to the age of the instrument. The microscope came to me also with a live box observation glass, a device very popular in the XIX century English microscopy practice, especially devised to ease the observation of live small acquatic animals (such as protozoa, unicellular algae etc.). The contraption is illustrated in the Carpenter's book (W. B. Carpenter, The microscope and its revelations. 5th ed. 1875, Churchill London).




A live box used in the XIX century

 

Based on the scarce historical information available, the microscope can none the less be accurately dated between 1863 and 1867, with the lower estimate more likely, according to the non standard RMS thread. The lacking of a serial number (a common event among small manufacturers) may suggest a small production, maybe made after specific ordering by customers.

 

James Blake Gardiner

Son in law of John King, a renowned scientific instrumant maker in Bristol, had his shop in 2 Clare street. J. B. Gardiner advertised his business as an optician at 2 Clare Street as a son-in-law to John King on newspapers from 1863 to 1865.

A full account of his life, based on my personal research can be found here.

Given the short time of his business, it is possible that the instrument shown above is one of the presumably very few surviving examples of microscopes made by this poorly known optician of the Victorian age

 

 


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