46
4 Observator and Professor
Father Kapteyn had wanted his son Jacobus to accept a position as a teacher.
An HBS was an excellent place to work for those young men that had obtained
a PhD. We saw earlier that his older brother Willem was a teacher at the HBS
in Middelburg when he was appointed professor in Utrecht. Such a job would
be an obvious choice for Jacobus as well.
What about military service, though? After all, all the healthy young men had
to fulfill military service. The archives of the municipality of Barneveld show
that Kapteyn had passed the medical, physiological and mental inspection.
The young men that would have to report for active service were determined
by drawing lots. Kapteyn was the fifth draw and would normally have had
to go and serve in the army, but that he had bought off by hiring a so-called
‘remplaçant’. This replacement was a man who had also passed, but in one way
or another was exempt from military service (e.g. when two older brothers had
already been in active service, or when he was a higher draw when sufficient
young men had been chosen). Hiring a remplaçant was reasonably expensive; it
cost like 600 to 800 guilders (about two years’ income of an unskilled worker),
of which a large part could be absorbed by mediators and civil-law notaries.
Only the reasonably wealthy could afford it.
The records in the Barneveld Archives on the selection also give us insight
into the height of Kapteyn. He was recorded as being 171.5 cm. For the 54
men approved in Barneveld in the same year as Kapteyn, the median was 167.2
cm, so Kapteyn was on the tall side, although not extremely so.
4.1 The Sterrewacht Leiden
Astronomy had been practiced in Leiden, as mentioned above, since shortly after the founding of the university. In 1632 Jacobus Golius (1596–1667) bought
a quadrant, which was built by Willibrord Snellius (1580–1626). Snellius used
this instrument to measure from one church tower what the angle was between
two other church towers in the distance. If you know the distance between the
two latter towers, you can calculate how far away you are from the first. By
moving on to other towers, you can finally measure the distance between two
fairly distant cities, which are chosen to be more or less on a north-south axis
(in this case Alkmaar and Breda, about 116 km apart, see Fig. 1.0). If you
then measure from these two places how high a certain star culminates above
the horizon (passes the meridian in the south), you can calculate from the
difference between those angles what the difference in geographical latitude
is and thus determine the circumference of the Earth. But you can also use
this instrument to determine angles between stars in the sky. The quadrant of
4 Observator and Professor
Father Kapteyn had wanted his son Jacobus to accept a position as a teacher.
An HBS was an excellent place to work for those young men that had obtained
a PhD. We saw earlier that his older brother Willem was a teacher at the HBS
in Middelburg when he was appointed professor in Utrecht. Such a job would
be an obvious choice for Jacobus as well.
What about military service, though? After all, all the healthy young men had
to fulfill military service. The archives of the municipality of Barneveld show
that Kapteyn had passed the medical, physiological and mental inspection.
The young men that would have to report for active service were determined
by drawing lots. Kapteyn was the fifth draw and would normally have had
to go and serve in the army, but that he had bought off by hiring a so-called
‘remplaçant’. This replacement was a man who had also passed, but in one way
or another was exempt from military service (e.g. when two older brothers had
already been in active service, or when he was a higher draw when sufficient
young men had been chosen). Hiring a remplaçant was reasonably expensive; it
cost like 600 to 800 guilders (about two years’ income of an unskilled worker),
of which a large part could be absorbed by mediators and civil-law notaries.
Only the reasonably wealthy could afford it.
The records in the Barneveld Archives on the selection also give us insight
into the height of Kapteyn. He was recorded as being 171.5 cm. For the 54
men approved in Barneveld in the same year as Kapteyn, the median was 167.2
cm, so Kapteyn was on the tall side, although not extremely so.
4.1 The Sterrewacht Leiden
Astronomy had been practiced in Leiden, as mentioned above, since shortly after the founding of the university. In 1632 Jacobus Golius (1596–1667) bought
a quadrant, which was built by Willibrord Snellius (1580–1626). Snellius used
this instrument to measure from one church tower what the angle was between
two other church towers in the distance. If you know the distance between the
two latter towers, you can calculate how far away you are from the first. By
moving on to other towers, you can finally measure the distance between two
fairly distant cities, which are chosen to be more or less on a north-south axis
(in this case Alkmaar and Breda, about 116 km apart, see Fig. 1.0). If you
then measure from these two places how high a certain star culminates above
the horizon (passes the meridian in the south), you can calculate from the
difference between those angles what the difference in geographical latitude
is and thus determine the circumference of the Earth. But you can also use
this instrument to determine angles between stars in the sky. The quadrant of