The instrument came to me with this condenser. Like the Universal, it has a larger diameter and a removable front element. The front element has a simple press-fit. This condenser is in a housing that has both a slide-out filter ring and an iris diaphragm. The optical component screws in to the housing and no part of this apparatus is signed, nor does it match any illustrations in the Watson catalogs.

Another mount holds the 'Holos Immersion Paraboloid' (HIP) which has an immersion front. It was available from no later than 1906 and continued to be offered throught the 1940s. The HIP can be used not only with oil immersion objectives, but also with moderate to high power dry objectives. When used with dry objectives, it still must be oiled to the bottom of the slide.  In these cases it can be used with a nosepiece iris ('Davis Shutter') without the need for a funnel stop but for oil immersion objectives, a funnel stop would be preferred. The paraboloid is signed:'Holos Immersion Paraboloid, No. 8068, slips 1.6 mm. The latter refers to the thickness of the slide with which the condenser is designed to work with (+/-20%). It is also signed 'W. Watson & Sons Ltd, London. The housing for the HIP has an iris but no flip out filter/stop holder like the other housings have, as this would have no purpose for a dark ground condenser. This condenser was introduced about 1909 and was reported in the JRMS of that year, part 5, p 647. The disadvantage of this dark ground condenser is that the maximum N.A. of the objective must be 0.95 or less, requiring higher N.A. objectives to be stopped down with a funnel stop, or by the use of a Davis (nosepiece) shutter.

About 1925, another dark ground condenser, designed by the eminent microscopist E.M. Nelson was released by Watson as Nelson's Cassegrain Dark Ground Illuminator. This condenser, which fits the same housing as the Holos Immersion Paraboloid, was also called Nelson's Reflex Condenser. This illuminator was designed for slides of 1 to 1.2 mm thickness. It was supplied with 2 different diameter stops, although only one labeled 16 is present with this example. This condenser has the advantage of allowing the full N.A. of oil immersion objectives to be used with N.A. up to 1.40. This type of high power dark ground condenser is much less complex and easier to manufacture than the cardioid type*, though the latter is usually optically superior.

*as found for example on Beck's Focussing Dark Ground Illuminator.

The large 'Polarizer for Petrological Work' comes with a large size prism and rotating flange divided and numbered with stops every 45 degrees. There was an optional condensing lens to fit over the polarizer but this is not present. This would have been useful for viewing conoscopic figures at high powers.

For lower power dark ground illumination, stops are provided both for the larger diameter 'Universal' condenser housing (not shown), and also for the Holos Oil Immersion condenser housing. There are also inserts for oblique illumination, and color filters as well.

Also with the microscope, as an alternative to the fixed stops, is a 'Dark-Ground Expanding Stop' originally called a 'Expanding Spot for Dark Ground Illumination' also known as a 'Traviss Stop'. W. R. Traviss first exhibited this device at the December 1906 meeting of the Quekett Microscopical Club and it was subsequently reported in the February 1907 edition of 'Knowledge & Scientific News' and in more detail on pages 362-364 of the JRMS for 1907.   This stop fits the filter holder for the smaller diameter fittings of the 'Holos Oil Immersion Condenser' and the 'Aplanatic Low Power Holoscopic Condenser.' The aperture can be varied from about ⁵/₁₆ to ½ inch; this range is smaller than the two ranges quoted in the 1912 catalog. With smaller diameters, this stop is suitable for a higher power range of objectives than the larger diameter example shown in the 1912 catalog. One would conceivably need both this one and the larger range examples to be able to provide appropriate stop sizes for a wide range of objectives.

OTHER ACCESSORIES:
Other accessories included five vertical illuminators. The first and third noted below are no longer with this microscope.

One is the type with a coverslip used as the reflector by Beck; this type of vertical illuminator was in use from the middle of the 19th century. This Beck illuminator, redundant with the next illuminator, is no longer with this microscope.

A second vertical illuminator by Watson, is similar to the first, but with the improvement of variable apertures for light entrance. It came in a signed can.

Another illuminator is a Zeiss prism type of vertical illuminator with oxidized-black finish. This illuminator is no longer with the microscope,since the combined illuminator in the next entry has the option of using a prism included in the kit.

Later the Watson 'Combined Vertical Illuminator' set was offered and is also with this instrument. The Watson 'Combined Vertical Illuminator' was first offered by Watson   after 1921, and is shown in the 1923 catalog (thanks to Dr Joe Zeligs for this information). The Combination illuminator came in a signed case, providing the option of a tiny prism or coverslip for reflecting the illuminating light beam.

Finally, a 'Watson-Conrady Condenser Vertical Illuminator' is also with the set and was the most advanced type of vertical illuminator available for many years. Vertical illuminators are used for illumination of solid or opaque objects with higher power objectives.   Light comes in from the side, and is reflected downward onto the object by the angled coverslip or tiny prism. The light is then reflected off the opaque object vertically, either around the tiny prism or through the coverslip.

There is a also an accessory stage plate 'for rough work' which slides in from the front of the stage into the dovetail slots which also accept the slide support bar.

A Watson 'Best' stage forceps with curving support also accompanies the instrument.

The 'Davis Shutter' is a nosepiece iris diaphragm. It can be used to increase the depth of focus, and also for dark field work, except with highest powers where a funnel stop* would be preferred. It was first suggested by Dr Royston-Pigott in 1869 for erroneous purposes, however it was first noted for its usefulness for 'increasing penetration' as described above on page 262 of the JRMS of 1882.  When the shutter is used to increase depth of field, resolution is reduced.   This instrument has one unsigned and another signed by Swift.

*A funnel stop is a tapered tube which fits inside the objective to narrow the diameter of the image emerging from the rear element of the objective, while blocking the more peripheral rays of light.  

A 'Botterhill Trough' (left) is also among the accessories. Viewing moving organisms with a microscope has always been a challenge. Various types of apparatus have been devised to contain and/or restrain such organisms. They vary from a simple small container to more sophisticated compressoria. One type of container is a trough and the type invented by Botterhill was offered by Watson from 1893 through the early 20th century. The Botterhill trough was first reported in the JRMS Volume 3, part 1, pages 148-149 in 1880 but was not offered in the 1883 Watson catalog.  In the 1880 report it specified the outer trough plates be made of brass, but they were soon offered made of Vulcanite as well, and the 1893 listings by Watson offered them in Vulcanite. The apparatus consists of two pieces of thin glass separated by a piece of 'India Rubber' and these resting inside the container of two Vulcanite plates each with a circular cutout and beveled edge. Three screws apply pressure to keep the apparatus water-tight. The thickness of the rubber spacer between the glass plates can be varied to suit the thickness of the animal being studied. The apparatus can be disassembled easily to allow the plates and rubber to be cleaned or replaced. According to George Davis, in 'Practical Microscopy of 1889, this device was first manufactured by Thomson and Capper of Liverpool, who also were the first to make Botterhill's 'Microscopic Life Slide' an example of which is also in this collection. The Life slide was noted in the 'English Mechanic and World of Science of June 3, 1881 page 298.

This is a Watson variation of Rousselet compressor, which was described by Rousselet in the 1893 volume of the JRMS. It illustrates the Watson modifications on the original Rousselet design. As shown here, it uses quick release fittings to hold the upper glass in place. Although this made changing the upper cover glass fast and easy, it was a distinct disadvantage over the method of gluing the top glass on, which then forms a seal, so that fluids like immersion oil would not seep under the top cover slip from above. (see Rousselet, CF, A Description of the Rousselet Compressorium, JQMC vol IX, 1904-1906 p 137-8). Please click on the image for more details and images.

This little bottle for immersion oil fits in a wooden cup on the door of the case.

Depression slides, usually made of solid glass now, were at one time made mostly of brass. They are used to study a small amount of liquid such as pond water, but unlike the compressor and some live boxes, have no mechanism to immobilize any swimming creatures.  Another disadvantage, if used with a coverslip,  is lack of facility of adding liquid as the original is evaporating.  Botterhill's life slide is a superior design in that respect. 

This stage micrometer is used to calibrate the eyepiece micrometer for each objective.

This 'Mica Selenite Stage' provides three different selenites in a slider with a rotatable mica disc above controlled by the knurled knob in center. This device would reveal a wide variation in colors of polarized objects-a very entertaining accessory. Click on the image to see the effects of this accessory.

This 'Selenite Stage' was a bit more expensive than the 'Mica-Selenite Stage' as it uses a geared mechanism to rotate the central well. The selenites were provided individually and as such could be used singly or combined. This accessory was offered by Watson for over sixty years! It gives a slightly wider variety in choice of effects than the Mica-Selenite Stage. Click on the image to see the effects of this accessory.

This is a livebox, intended to allow observation of living specimens. It consists of a short tube or barrel, the top of which is covered with glass. A liquid or solid specimen can be placed here. The cap, with a glass top can then be pushed down over this barrel of the slide to contain the specimen, either with no pressure or with some degree of pressure as desired. The degree of pressure applied cannot be varied as precisely as it can be in the modified Rousselet compressor shown above. This livebox has the typical small holes to either side of the cylinder, also found on other Watson liveboxes. Rousselet also popularized an improved livebox(though it was invented much earlier), and Watson was among those who made them (see next entry).

This is a livebox, intended to allow observation of living specimens, similar to the preceding entry. This later version was popularized about 1887 by Charles Rousselet, FRMS, though it turns out it was invented much earlier, by Blankley as reported in the English Mechanic and World of Science, No. 305, Jan 27, 1871, p 437. It is similar in some ways to the Varley livebox. In this variation, the lower glass is a raised 'tablet' with chamfered edges at the bottom of the cylinder. The upper portion or 'cap', instead of fitting around the outside of the bottom cylinder fits inside it. Also instead of the glass on the top of the second cylinder, it is on the bottom, so as to meet the tablet. Furthermore this upper cylinder is actually a double cylinder with its inside part threaded to the outer part, thus holding the glass in place. This allows the glass to be changed in or out without the need for glue. This livebox has two holes similar to the preceding example but this one is signed: 'W. Watson & Sons Ltd., London'. This would date this to after 1908. This design is like Rousselet's form, not the early twentieth century modification by Merlin. These types of live boxes were also made by Smith, Ross, Swift, and likely others. For more images of this livebox, please click on the image. An example of this type of livebox sold by Swift around 1877 is on this site.

This device is an 'object marker.'   It is used to inscribe a circle around an area of interest on a slide or coverslip on a slide. It makes use of a small diamond. In use, the microscopist centers the area of interest, and then replaces the objective with this device. It is spring loaded. As the optical tube of the microscope is lowered onto the slide, the spring applies just enough pressure. The user rotates the diamond via the knurled ring. A small knob adjusts the size of circle the marker produces; it is difficult to use the device if a very small diameter circle is chosen. This device was first invented by Leitz in the first decade of the twentieth century, and then copied by Watson. It is not listed in any Watson Catalog that I could find. Another form of object marker also fitting on the nosepiece, was used to simply stamp an area with ink. This stamping device was devised earlier than the diamond marker, and obviously made a circle that was not as durable, though more easily seen with the naked eye than the diamond mark. In the twentieth century, Nikon produced a modern form of stamping object marker which actually had an ink resevoir.

Watson & Sons had been making microscopes since about 1874. For some time in their early production, their microscopes were similar to other contemporary makers, but soon they started to produce a variety of interesting designs, including their own variation of the Walter Bulloch Biological No. 2, and also a version loosely based on Wale's New Working Microscope.   In 1887, Dr Edington, a Lecturer in Bacteriology from the University of Edinburgh, suggested the first form of the Edinburgh stand; according to Watson's delivery records, the first example was sold on November 29, 1887. This stand was the inspiration for the Van Heurck stand, and like the Van Heurck, started out with a continental foot, but was soon ordered more often with a tripod foot. Like the Van Heurck, it was improved progressively over the years. This culminated in the Edinburgh 'D' and 'H' models, (an example of 'D' is shown to the left), which had most of the basic features of the (later) 'Royal' model. In fact, when the Royal was first introduced, it was actually slightly smaller than the Edinburgh H.  The various Edinburgh stands were at first indicated by the numbers 1,2,3, and 4, but by 1890, the letters A,B,C and D were used. 

In 1889 or before, with all of his expertise, Van Heurck suggested the design of a microscope to his specifications, and this was the first model of the Van Heurck microscope made by W. Watson and Sons. The first entry for a  Van Heurck in the Delivery Books was for serial number 2641 on March 17, 1891*:

This microscope was pictured in the first edition of Van Heurck's book also dated 1891.  This first version is identical to the 'Watson No. 4 Van Heurck Stand A' seen in the 1893 catalog. Study of the illustrations shows that this initial Van Heurck differed from the original Edinburgh mainly in two features-the fine adjustment for the substage, and the ability to rotate the entire mechanical stage. Van Heurck preferred to do all of his photomicrography with a vertically oriented microscope which is why he preferred his microscope to be made with a continental horseshoe foot and supported on a single pillar, so as not to interfere with substage adjustments during the, (then) delicate operation, of photomicrography with high power objectives. At the same time, many others preferred the horizontal position for photography. For this reason, his stand was also offered with the more stable English tripod foot which provided a much more stable stand for photography in the horizontal position. Many more examples with an English tripod exist than with the horseshoe foot, as the tripod quickly became more popular.

*An engraving of the Van Heurck 'A' stand found in a bound volume of catalogs as the first page of an 1889 Watson catalog. This microscope was not listed in the catalog, and the page, which is also slightly smaller than the pages in the rest of the catalog, has a horizonal fold suggesting it was not original to that catalog, and was simply tipped in, in front of the rest of the Watson 1889 catalog when it was bound together with the other catalogs in this bound volume of catalogs. Therefore, although the author of this web page previously thought this might be an original part of the catalog, and dated the first Van Heurck microscope to 1889, it seems that this is not true. A search for another 1889 Watson catalog has not been successful so far. We are grateful to Jeroen Meeusen, the owner of this 1889 catalog, for pointing out this information.

As noted above, the Van Heurck instrument, as designed by the diatomist, was at first provided on a continental foot with a single pillar. Early examples had a standard one inch diameter main optical tube, as pictured in the image in the preceding paragraph. In the 1893 catalog the 'No. 4 Van Heurck Stand A' had a 1 inch diameter main optical tube with a single calibrated draw tube with tube length variable from about 160 mm to 260 mm. The 'No. 4 Van Heurck Stand B,' as shown to the left, had a double drawtube, the lower draw wider, (but still only 1.5 inches in diameter), and controlled by rack and pinion. In the 'B' stand the combined tube length could be varied from about 142 to 305 mm. It could be ordered as pictured with a continental foot, or for a slightly higher price with a tripod foot. The Van Heurck was apparently not yet considered the 'top of the line' instrument as No. 1 was the impressive 'Watson Swinging Substage Microscope,' No. 2 was the 'Scientist's,' and No 3. was the 'Research.'

In 1896, stand 'A' was no longer listed, but the usual Van Heurck was still called the 'B', available with a continental or, as seen to the left, a tripod foot  Also in 1896, the 'Grand Model Van Heurck Microscope Stand' (right) was first listed in the catalog. At that time it was listed as identical to the B stand except for three new features: 1)concentric controls for the mechanical stage (after Terrell), 2)complete rotation of the stage, and 3)a slightly larger foot with the Grand, the spread of the foot 'more than ten inches'.

The 'Circuit Stage Van Heurck' was apparently first introduced about 1899 (as quoted in the Illustrated Annual of Microscopy for 1900). Like the Grand Model, it had complete rotation to the stage, but was otherwise identical to the smaller Van Heurck (now just called the Van Heurck without a letter or number), including the stage controls. Later on, the basic model simply became the 'No 1 Van Heurck'. 

Although listed in the Watson 1900 catalog, the Circuit Stage Van Heurck was not illustrated in that volume. The engraving to the left, from the 1902 catalog, illustrates the Circuit Stage Van Heurck with the optional Watson-Males two speed fine adjustment. It should be noted that from the start, the Terrell type stage could be ordered as an option for the Circuit Stage Model, thus some might look like a 'Grand' but would be distinguishable only by size.

To satisfy growing demand for a stand as perfect as the Van Heurck but slightly smaller and therefore less costly, the 'Royal' model was introduced about 1899-1900 as well. The major distinguishing feature between this and the No 1 Van Heurck, was the inability to rotate the mechanical stage (although some models with a rotating top plate are known); it was also of slightly smaller size than the Van Heurck, and initially was even slightly smaller than the Edinburgh H stand. In fact, it is a common misconception that the 'Royal' is generally a larger stand than the 'Edinburgh H' and this is not true. The tripod heights, arm/limb size, foot spread and stage are of identical size in many examples; what makes the 'Royal' appear larger is the larger diameter optical tube and drawtubes including the rack and pinion draw tube. Without these differences and the fact that some 'Royals' have a substage fine focus, the Edinburgh H and the 'Royal' could not be differentiated from one another. This is confirmed by the examples in my collection; the 'Royal' and Edinburgh are virtually identical in size and differ mainly in the diameter of main optical tube, the Royal's double draw tube, and fine focus for the substage.

CHRONOLOGY OF EVENTS IN THE DEVELOPMENT OF THE EDINBURGH, ROYAL, AND VAN HEURCK SERIES OF MICROSCOPES:

• 1874-: Watson starts to produce microscopes.
• 1874-1887: Watson produces microscopes of the usual designs but eventually makes their own version of other famous stands including those of the American makers, Bulloch and Wale.
• 1887: The first Edinburgh microscope is sold, based on suggestions by Dr. Edington of Edinburgh.
• 1889: Henri Van Heurck proposes the initial design for his microscope.  
• 1891: The first entry in the Watson Delivery Books of a Van Heurck microscope, being based on the Edinburgh stand. It had a 'horseshoe' foot.
• 1893: The Watson Catalog offered the No. 4 Van Heurck microscope in two versions both with a horseshoe foot; Stand 'A' had only a single drawtube and did not have a rack and pinion adjustment to the drawtube. Stand B had a larger diameter main optical tube with two drawtubes, the lower one adjustable by rack and pinion. Either version could be obtained with a tripod foot as an option for additional cost.
• 1895: The 'Grand Van Heurck' is first offered, and is seen in the 1896 catalog with the new features being complete rotation to the stage, the concentric controls for the mechanical stage, and the slightly larger size of the stand. The Van Heurck 'B' is offered but the 'A' with single drawtube is no longer mentioned. The grand is 7/8 inch taller than the 'B.'
• 1900: The 'Circuit Stage' Van Heurck Model is introduced. It has the complete rotation of the stage but is otherwise identical to the 'B' stand.
• 1900: The 'Royal' is also introduced,  smaller than the Van Heurck models, but with options for almost all the same features except for stage rotation; the 'Royal' was never offered with stage rotation.  It is initially slightly smaller than the Edinburgh 'H' model!   Standard features included the double drawtube with rack and pinion adjustment to the lower one.  Initially, substage fine adjustment was standard on the 'Royal' but located under the stage near the substage coarse adjustment.  Later this became optional.  

*-It becomes even more confusing, because eventually, even the rack and pinion adjustment for the drawtube could be ordered as an option on 'lower class' microscopes such as the Edinburgh stand.

OPTIONS FOR THE MICROSCOPES:
The following table lists options (including optional deletions) for the Edinburgh, Royal and Van Heurck Models. It may be incomplete, as the author has not had access to every single Watson catalog relevant to the period.