Let us return to our instrument. We have traced upon a diagram the
distance of the points of attachment of the thread, at the
intersection of the planes of projection. We have thus obtained the
position of the line, N S. Then, operating as has just been said, we
have marked the point, P. Now, accurately measuring all the angles, we
have found: N S R = 50 deg.; P H H? = 18 deg.; P E E? = 65 deg.. The first shows
that the instrument has been constructed for a place on the parallel
of 50 deg., and the others show that, at the solstices, the height of the
sun was respectively 18 deg. and 65 deg., decompounded as follows:
18 deg. = polar height of the place -231/2 deg..
65 deg. = " " " " +231/2 deg..
The polar height of the place where the object was to be observed
would therefore be 411/2 deg., that is to say, its latitude would be 481/2 deg..
Minor views of construction and measurement and the deformations that
the instrument has undergone sufficiently explain the divergence of
11/2 deg. between the two results, which comprise between them the latitude
of Paris.
After doing all the reasoning that we have just given at length, we
have finally found the means by which the hypothetic bead was to be
put in place.
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