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The Watson "Histology" model, 1891




Watson compound microscope "Histology" stand, 1891

This is a second-class microscope, suited for routine histological work or advanced students. Watson introduced the histology stand in 1886. The microscope is engraved on the foot W.WATSON & SONS, 313 High Holborn, London and bears the serial number 2670, dating it to 1891. It has a rack and pinion mechanism for course focusing, while the fine focusing is attained by a micrometer screw on the milled head. This particular fine focusing adjustment was introduced by Watson in 1889 as illustrated in Carpenter's book "The microscope and its revelations".

 




Excerpt from W. B. Carpenter "The microscope and its revelations", 8th ed., 1901, illustrating the new fine focusing mechanism devised by Watson.

A draw-tube allows further adjustment of the magnification according to the objective used. A double-sided plano-concave mirror provides illumination. Under the square stage with slides clips, it is present a plug-in diaphragm whose aperture can be varied by screwing on it a top element with a small aperture hole, to regulate the amount of light. The microscope came to me in its original mahogany case, with one eyepiece and two objectives: a Watson 1 inch and an unmarked 1/6 inch, both with matching brass canisters. I refurbished the instrument by separately acquiring a XIX century 1/8 inch objective signed W.A. Pyall (Peckham) with matching canister and two eyepieces: a 10X Watson holo and an unmarked 8X, both dating end XIX-early XX century. It must be noted that the tube diameter was an unusual 28 mm (instead of the 23 mm that became the standard a few years later). Thus, I am using an adapter, realized using a brass ring acquired separately with a lot of spare pieces for XIX century cameras fittings (it can be seen behind the microscope, fitted to the 10X Watson eyepiece). I also refurbished the instrument with a XIX century double rotating nosepiece (shown in the picture with the 1/6 and 1/8 objectives). Since no Abbe's condenser was present, I built one from original late XIX century spare parts I had, using the field lens of a 4X ocular, held in place on the underside of the plug-in diaphragm by two concentric brass rings (also part of that lot of spare parts mentioned above). The contraption is pictured below mounted on the microscope.

 




Home-made condenser realized fitting the barrel and field lens of a 4X ocular to the under stage

All optics are excellent and with the 10X eyepiece and the 1/8 inch objective, an approx. magnification of 750X can be obtained. The picture below shows mitotic divisions in human cells observed at c.a. 500X.

 




Mitotic divisions in HeLa cells, 500X (picture taken with a Canon digital camera)

 

Watson & son firm

The Watson company was founded in 1837 in London.  In 1868 the firm's name was changed to W. Watson & Son and they were located at 313 High Holborn, London. They continued at this address well into the 1940s.  In 1881 the founder, William Watson, died and in 1883 the firm's name was changed to W. Watson & Sons, since William's son, Charles Henry Watson, joined the business. In the 1890s the business continued to grow and they advertised factories for instruments, optical glass and cabinet work at Fullwood Rents W.C. while the warehouse and show room remaining at the 313 High Holborn.  In 1900 W. Watson & sons purchased another historical English microscope firm, the John Browning & Co.  In 1908 the firm became W. Watson & Sons Ltd. In 1948 the business dissolved. Watson produced some of the finest and technically most sophisticated microscopes of late XIX - early XX century, among them the highly sought (and priced) Edinburgh, Royal and van Heurck models. For more details on the firm see Brian Bracegirdle's book "Notes on Modern Microscope Manufacturers".

 


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