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578 [ Doc. 200.
SWEDENBORG AS A MAN OF SCIENCE.
C.
PROFESSOR A. CELSIUS 144 REPLY TO ASSESSOR SWEDENBORG’S CALCULATION
OF THE DECLINATION OF THE MAGNET FOR THE MERIDIAN OF UPSAL. *
As Assessor Swedenborg has now been pleased himself to
calculate the declination of the needle according to his theory,
and as he has found the same to agree pretty well with the
observation I took here at Upsal, when yet following the com
putation of Magister Hiorter I had stated it to differ by 8° 13 ’;
I have therefore examined Magister Hiorter’s calculation, and
find it to agree with the rules and examples laid down by the
Assessor in his philosophical work. But, on the other hand,
I notice that the Assessor’s own computation agrees with
my observation, by mere chance ; it being extremely faulty, espe
cially from his having taken the latitude of Upsal, instead of its
complementum or elevatio æquatoris. I have therefore the
honour of communicating to the Academy of Sciences Magister
Hiorter’s computations for the meridian of Upsal, and also
the mistakes which occur in Assessor Swedenborg’s calculation,
from which the Academy of Sciences can see clearly that the
difference pointed out by me is not due to any error in Magister
Hiorter’s computation, but results from the theory itself; which
is the less surprising, as Assessor Swedenborg was unable to
obtain as many observations of the declination and inclination
of the needle taken around the whole globe with sufficient
accuracy, as allowed him to construct from them a theory
so perfect that it needed no alteration and improvement by
more recent observations. I believe that Dr. Halley55 has
more than any other applied the deepest thought in establish
ing a theory of the declination of the magnet which the learned
have been seeking to improve ever since ; yet he does not
venture to determine by geometry the situation of the magnetic
poles upon the earth, and to establish rules for computing
the declination. Meanwhile, however, he has empirically con
structed crooked lines representing the declinations of the
* This paper was read before the Academy of Sciences, on January
23, 1741.
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