parts, scarce failing as much as
in one only part, so as we can in a manner be _assur'd_, not to deceive our
selves in 3. or 4. _seconds_. I shall not now tell you my Observations, but
I may very well assure you, that the _Diameter_ of the _Sun_ has not been
much less in his _Apogee_, than 31. m. 37. or 40. sec. and certainly not
lesse than 31. m. 35. sec. and that at present in his _Perigee_ it passes
not 32. m. 45. sec. and may be lesse by a second or two. That, which is at
the present troublesome, is, that the _Vertical_ Diameter, which is the
most easie to take, is diminisht, even at _Noon_, by 8. or 9. sec., because
of the _Refractions_, which are much greater in Winter than Summer at the
same height; and that the _Horizontal_ Diameter is difficult, because of
the swift motion of the Heavens.

As for the _Moon_, I never yet found her Diameter less than 29. m. 44. or
45. sec. and I have not seen it pass 33. m. or if it hath, it was only by a
few _seconds_. But I have not yet taken her in all the kinds of situations
of the _Apogees_ and _Perigees_ which happen, with the _Conjunctions_ and
_Quadratures_. I do not mention all, what can be deduced from thence, but
if you have Persons at _London_, that observe these _Diameters_, we may
entertain our selves more about this Subject, another time. I shall only
tell you, that I have found a Way to know the _Parallax_ of the _Moon_, by
the means of her _Diameter_: _Vid_. If on a day, when she is to be in her
_Apogee_ or _Perigee_, and in the most _Boreal_ Signes, you take her
Diameter towards the _Horizon_, and then towards the _South_, with her
_Altitudes_ {374} above the Horizon. For, if the Observation of the
Diameters be exact; as in these Situations the Moon changes not
considerably her Distance from the Earth in 6. or 7. hours, the
_Difference_ of the Diameters will shew the Proportion there is of her
Distance, with the Semi-diameter of the Earth. I do not enlarge, because
that as soon as one hath this _Idea_, the rest is easie. The same would yet
be practis'd better in the places, where the Moon passes through the
_Zenith_, than here, for the greater the difference is of the Heights, the
greater is that of the Diameters. I do not note (for it easily appears)
that, if one were under the same _Meridian_, or the same _Azimuth_ in two
very different places, and took at the same time the Diameter of the Moon,
one would do the same thing, though this Method goes not to precise