ness.

From what has been said, may be collected the reason of the Observation,
which M. _Hevelius_ made in the last _Eclipse of the Sun_, touching the
increase of the Moon's Diameter about the end. I am exceeding glad, that a
person, who probably knew not the cause of it, has made the Experiment: but
it is strange, that until now no Astronomer has foreseen, that that should
happen, nor given any precepts for the Change of the _Moons Diameter_ in
the _Eclipses of the Sun_, according to the places, where they should
happen, and according to the Hour and Height, the Moon should have. For,
what hapned in that _Eclipse_ of Augmentation, would have faln out
contrarily, if it had been in the Evening; for, the Moon, which in that
_Eclipse_, that began in the Morning, was higher about the end than at the
beginning, was nearer us, and consequently was to appear bigger: But if the
_Eclipse_ should happen in the Evening, she would be lower at the end, and
therefore more distant from us, and consequently appear lesser. So also in
two different places, whereof one should have the Eclipse in the Morning,
and the other at Noon, the Moon should appear bigger to him that hath it at
Noon: And she must likewise appear bigger to those, who shall have a leser
_Elevation_ of the _Pole_ under the same _Meridian_, because the Moon will
be nearer them.

I wish, I could satisfie you about the _Optick Glasses_ of Signior
_Burattini_ in _Poland_, which he hath sent hither; but I have not yet seen
their performances my self. I only saw once the Glasses, {375} which are
perfectly well wrought and well polisht. Those, that have tried them, find
them very good; but they are only, the one of 10, the other of 8. foot. A
good Astronomer told me, that they would bear a great _Aperture_ in respect
of their length.

I do not well know, what to say to yours concerning M. _Hevelius_. Mean
while, the interest of truth, and the obliging manner, he has treated me
with, engage me to answer him, in the matter of the _Comets_: I am
perswaded, I shall convince him; but since he hath taken the _Illustrious
Royal Society_ for Judge, I accept that with all my heart.

* * * * *

_A Relation of the loss of the Way to prepare the _Bononian Stone_ for
shining._

[Sidenote: * It is hoped notwithstanding (which also a late Letter from
abroad does hint) that some or other of the _Italian_ Vertuosi at
_Florence_ have secured this Secret.]