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Volkert Simon Maarten van der Willigen
(1822-1878). Lithograph by J.P. Berghaus.
(Iconographisch Bureau, Den Haag).
abroad, doing repairs and demonstrations, and collaborating in some
publications as co-author. He customarily submitted a monthly
account for his time and expenses. His work was concerned in the main
with electricity and magnetism.
Even if the published papers were short on novel ideas, Teyler's continued
to be fully up to date in buying the latest inventions in apparatus for
demonstration, whatever the cost. The first item bought by Van Breda
was a daguerreotype camera by Giroux of Paris, purchased in 1840 for
Dfl. 210.44 (now lost). There followed a thermoelectroscope; a microscope
by Powell & Lealand of London, the best makers of microscopes
in the world at that time; a thermoelectric bench with all the apparatus
of Melloni, by Ruhmkorff of Paris; a differential tangent galvanometer
1.25 metres in height, designed by Elias, a lawyer of Haarlem, and
made by Logeman; a model of a Foucault pendulum; an induction coil
by Ruhmkorff; a Newton's rings apparatus; a device to produce
Lissajous figures using light beams; a Bramah hydrostatic press, made
by Logeman and Funckler; and ten Geissler tubes from the inventor in
Bonn.
Van Breda's main interests were in plants and fossils, and he did not
publish a great deal on the physical sciences, only twelve papers five of
which were with co-authors. His first paper on physics came in 1845,
on the thermoelectric effect, followed by others to do with electromagnetism,
and four in co-operation with Logeman, all of which were concerned
with electrical conductivity. Logeman also published three times
by himself, all on electromagnetic effects.
There was a gap of nine months between the resignation of Van
Breda in 1864 and the taking up of the post of Conservator of Teyler's
Physical Cabinet by Volkert S.M. van der Willigen (1822-1878). It was
at this time that the link with the Hollandsche Maatschappij was broken.
Teyler's organization was by now more varied and extensive. While Van
Breda had been in charge of the Physical Cabinet and the
Paleontological-Mineralogical Cabinet, and Van Marum had managed
the cabinets plus the library, Van der Willigen was in charge of the
Physical Cabinet only. Van der Willigen published 51 papers between
1854 and 1878, the year of his death; the first on an optical illusion,
and the last on artificial magnets. He was interested in light, whether
inside an electric egg or in Newton's rings. But, unlike his predecessor,
one can detect a period during which he pursued a series of experimental
researches all linked to one theme, that of the standard of length.
Once this thread is detected, a new approach becomes necessary to the
instruments in the New Museum. They are placed in ten cases in
roughly subject grouping, but a different grouping now becomes possible,
cutting across the case arrangement. So what was the programme
of Van der Willigen?
In September 1851, the Minister of Internal Affairs asked the
Koninklijke Akademie van Wetenschappen to look into standards of
weights and measures, referring to the law of 1816 that adopted the
French standard of length based on the quadrant of the Earth. It was
notorious that the French made an error in the measurement, which
V.S.M. van der Willigens Observatory,
1867 (photograph 1986).
was too short. In effect, the standard platinum metre was no better than
the old standard. Committees sat and reports were published. New substandards
were made and compared with the French original in Paris. A
standard metre in glass was produced in 1856 by the firm of Olland in
Utrecht, and Teyler’s Museum was given Number 9, bearing the wax
seal of the Koninklijke Akademie van Wetenschappen. At the same
time, copper kilograms were made by E. Wenckebach, and Teyler's
received Number 1, fire-gilded on the surface. These standards were
rectified by small pieces of platinum wire placed in a cavity underneath
the knob, which unscrews. It does not need to be said that science cannot
progress if standards of measurement are not universal, thus making
results obtained anywhere intercomparable. With ever-increasing
accuracy of measurement, standards have to be constantly refined, even
by changing the method of measurement, as is seen when the mechanical
clock was replaced by the more accurate quartz crystal, and that in
its turn by the atomic clock. Up to I960 the standard of length was
based on the wavelength of light emitted by a chosen element (krypton),
and it was towards this that Van der Willigen was moving in his work.
The present-day standard of length is based on the velocity of light (the
laser definition of 1983).
The Swedish physicist, Anders J. Angstrom (1814-1874) at the
University of Uppsala published a classic work on the nature of the
spectral lines in the solar spectrum in 1855. In the following year, Van
der Willigen published a séries of papers on the electric light spectrum,
and then on interference and on accurate determinations of the refractive
index, which occupied him for more than ten years. The move to
Teyler's brought a break in publication of about a year; then he resumed
with a long paper on the determination of the wavelengths in the solar
spectrum, dated May 1866, and published as the first paper in the first
fascicle in volume I of the new Archives du Musée Teyler, which, containing
four fascicles, was published in 1868. In 1868, Angstrom published
in Uppsala his Recherches sur le spectre solaire. In order to establish spectroscopy
as one of the most powerful chemical analytical tools, it was
necessary to measure exacdy the wavelengths of the spectral lines. This
Angstrom did, using the standard metre at Uppsala University and the
diffraction gratings made By Friedrich Nobert (1806-1881) of