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Doc. 203.] 595
SCHENMARK TO SWEDENBORG .
the moon always a little below the ecliptic) by supposing the
moon’s distance below the point where the moon’s vertical
circle meets the ecliptic, to be the same in magnitude as the
moon’s parallax; or what is the same thing, that when the
moon is observed, it has apparently the same longitude as
the fixed stars s and t, although it has no true latitude. If
this is so, although it is not expressly stated by you , it may
yet be concluded from it that ) b in the printed figures is
always taken for the parallax of altitude; in which case I am
quite willing to admit that the method is so far correct, un
less the refraction causes some difference, which, whenever
the stars and the moon are at unequal heights above the
horizon, disturbs their relative positions; but of this no men
tion is made in the method .
New difficulties, however, arise here of a different kind
which are no less important: first, how can I be assured
that the moon at the time when it is observed at sea is
really in the ecliptic, or that the true place of the moon has
no latitude; secondly, as this happens but very rarely, it
follows that seamen can make use of this method only very
seldom, in case information can be obtained respecting what
I mention in my first, But, suppose, I have information on
this subject, in that case I already know what I desire to
know, and it cannot be taken for premises without beging
the question (præmissa sine petitione principii). Besides,
the astronomical tables are unable to furnish me with this
information ; for they tell me indeed the time under their
meridians when the moon has no latitude, but they do not
tell it to me under my meridian, which is unknown and in
question.
As my objections are the same in the second case when
the stars have both an unlike latitude and longitude as in
the first case, I must conclude here ; while I ask for the
honour of remaining in the future with all due respect,
Your obedient servant,
N. Schenmark.149
Lund, March 22, 1767.
38*
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