Geoscience Reference
In-Depth Information
Paris in time, the Conference was postponed until November. Delambre had to have
something to report, preferably side by side with Méchain. Delambre traveled to
the cities of Narbonne and Carcassonne in the south of France, closing in on
Méchain. Méchain persisted in refusing to meet him, making a succession of
excuses but at last they met early November 1798. At first Méchain was adamant
that he would not return to Paris and reveal the perceived inadequacy of his work.
He needed more time to polish the work before exposing it to foreign scientists,
stating, “I will not expose myself to this final humiliation.” It was not as bad as Méchain
thought, though, because the Bureau of Longitudes had agreed that Méchain would
be the next Director of the Observatory. Whatever he thought of his own work, others
respected his capability, and Méchain eventually agreed to return to Paris to attend
the International Conference and to hand over the data. In mid-November 1798
Méchain and Delambre returned to the capital, to a reception given by government
ministers and the entire Academy of Sciences for the visiting foreign scientists and
the two French scientist-heroes who had taken the measure of France against the
tribulations of the times.
The International Commission set up a competition between the two astronomers.
They would each determine the latitude of Paris and use their measurements to cal-
culate the meter separately in terms of the distance to Dunkerque and to Barcelona.
The degree of agreement would demonstrate the accuracy that had been achieved.
This was Méchain's nightmare come true; he was as unsure of his data as ever. While
Delambre presented his data to the International Commission who went over it detail
by detail and accepted the measurements, Méchain refused to hand anything over and
the international scientists became restless. The Danish astronomer Thomas Brugge
began to conclude that the whole thing was a sham and left for Copenhagen in
January 1799. Méchain was ordered to hand over his data and agreed to provide an
edited summary, which he did in March 1799. It must have been a relief to Méchain
that the International Commission found everything in superb order. As later develop-
ments showed (below) he had successfully pulled the wool over their eyes.
The Commission's members individually set out to combine all the measure-
ments and to calculate the final results which were stunningly unexpected. The
Earth was certainly not an ideal sphere, that was already known from the earlier
surveys by the Cassinis, but it was not a uniform ellipsoid either, not even any solid
that could be created by revolving a curve about the Earth's axis. The flattening of
the Earth was different, as measured in different segments of the Paris Meridian.
The measurements revealed the irregularities of the Earth's surface and that not all
meridians were the same.
The International Commission could not determine a consistent value for the
overall flattening of the Earth so it decided to adopt the value from the longest
survey of the Paris Meridian into Lapland, together with the measurements made in
Peru, and to apply it to the new data to estimate the circumference of the Earth from
equator to pole; from this followed the standard length of the meter.
FOR PRACTICAL PURPOSES, a platinum rod was produced that was supposed
to merely represent the ideal, unchanging length of the meter because it was more
