DESCRIPTION:

We are grateful to Dr Jurriaan de Groot for sharing his instrument, and this discussion with us:

This brass microscope and its components are stored in a rectangular mahogany case measuring 58 x 172 x 200 mm, which also serves as the base for the microscope when in use.

A rectangular section upright pillar is fitted with a dove-tail slider at its lower end, which slides into its counterpart on the right side of the case. The upper end of the pillar supports the horizontal limb, the distal end carrying a dove-tail slider with four objective lenses of different focal lengths. The compound optical tube is 102 mm long, and screws into the circular upper part of the limb. The push-in eye piece is of Huygenian design, with an eye and field lens. A single milled knob acts on a rack and pinion which focuses the cruciform stage, in which are two small holes for accessories apart from its central aperture. Illumination is provided by a single-sided concave mirror. The microscope is signed on the upright pillar facing the mirror: 'C. Schmalcalder, 82 Strand'. When in use the instrument stands 250 mm tall.

Accessories include:

1. Brass slider with four objective lenses
2. Stage bullseye condenser
3. Stage condenser
4. Fish plate
5. Wet-cell slider
6. Bonanni-type spring stage
7. Stage forceps
8. Small brass tweezers
9. Three bone sliders
10. Small round watch-glass fitting central aperture
11. George IV farthing coin (¼ p.) dated 1826 fitting central aperture in lieu of white/black disc (period replacement!)
12. Glass tube with cork stopper (period replacement)

Originally, this microscope set would have come with another brass slider for Lieberkuhn objectives. These are no longer present.

Optical data for use with compound tube, obtained with stage micrometer and Cheshire apertometer:

OBJECTIVE	MAGNIFICATION	APPROX N.A.
1	37x	0.06
2	45x	0.09
3	87x	0.12
4	140x	0.14

HISTORY PERTAINING TO THE SCHMALCALDER MICROSCOPE:
Karl August Schmalcalder was born on 29 March 1781 in Stuttgart, Germany. Upon moving to England in 1800 he anglicized his name to Charles Augustus Schmalcalder, and established himself in London, where he married Anne Cochrane in 1804 in St Andrews, Holborn, London. They had nine children, of which sons John Thomas, George (both apprenticed to Thomas Gilbert in 1829) and Joseph would also join in the mathematical instrument trade. Carl Schmalcalder worked as a mathematical instrument maker and retailer, from 1806 from his own premises in 6 Little Newport Street, St. Annes, Soho. Subsequently, he traded from the 82 Strand address between 1810-1826, before removing to 399 Strand in 1827, where he continued until 1840. He developed and patented several mathematical instruments, most famously the prismatic compass. He was succeeded by his son John (traded 1841-1845). Sadly, Charles Schmalcalder ended his life in reduced circumstances. He died on the 25th December 1843 in the Strand Union workhouse for the poor on Castle Street, St. Pancras, from injuries sustained as a result of having been run over by a horse and carriage some weeks earlier.

It is likely, that this microscope was made for the trade, and Schmalcalder was the retailer. An identical microscope signed: “Thomas Rubergall, Optician to the King, 24 Coventry Street, London” is in the Boerhaave Museum collection in Leyden, Netherlands.

Thanks to research kindly provided by Dr Brian Stevenson, and as posted on his site, Microscopist.net, it would appear, that this model microscope was first designed by Timothy Lane (1734-1807), an apothecary, scientist, and inventor. It was made and sold by Thomas Harris & Son, whereas other examples featuring some minor differences in the dovetail - and mirror mount, as well as the case were signed and probably made by Thomas Rubergall, and there is an almost identical microscope signed by him in the Boerhaave museum collection in Leyden, Netherlands. This particular example signed by Schmalcalder has the same features as the Rubergall instrument, and Schmalcalder was probably the retailer.