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Of _Monsieur _Hevelius_'s Promise of imparting to the World his Invention
of making _Optick Glasses_; and of the hopes given by Monsieur _Hugens_ of
_Zulichem_, to perform something of the like nature; as also of the
Expectations, conceived of some Ingenious Persons in _England_ to improve_
Telescopes.

That eminent Astronomer of _Dantzick_, Monsieur _Hevelius_, writes to his
Correspondent in _London_, as followeth:

What hath been done in the grinding of Optick-glasses in your parts, and
how those beginnings, mentioned by you formerly, do continue and succeed, I
very much covet to hear, 'Tis now above Ten Years, since I my self invented
a peculiar way of grinding such Glasses, and reduced it also into practice;
by which 'tis easie, without any considerable danger of failing, to make
and polish Optick-glasses of any _Conick_ Section, and that (which is most
notable) in any dish of any Section of a _Sphere_: which Invention I have
as yet discovered to none, my purpose being, for the Improvement of Natural
Knowledge, to describe the whole method thereof in my _Celestial Machine_,
and to propose it to the Examination and Judgment of the _Royal Society_;
not doubting at all, but they will find the way true and practicable, my
self having already made several Glasses by it, which many Learned Men have
seen and tryed.

Monsieur _Hugens_, inquiring also in a Letter, newly written by him to a
Friend of his in _England_, of the success of the attempts made by an
ingenious _English_ Man for perfecting such Glasses, and urging the
prosecution of the same, {99} so as to shew by the effects the
practicableness of the Invention, mentions thereupon, That he intends very
shortly to try something in that kind, of the success whereof he declares
to have good hopes.

Monsieur _du Son_, that excellent Mechanician, doth also at this very
present employ himself in _London_, to bring _Telescopes_ to perfection, by
grinding Glasses of a _Parabolical_ Figure, by the means whereof he hopes
to enable the Curious to discover more by a Tube of one Foot long, or
thereabouts, furnished with Glasses thus figured, then can be done by any
other Tubes of very many times more that length: The success hereof will
('tis thought) shortly appear.

* * * * *

_An Advertisement of a way of making more lively Counterfeits of Nature in
_Wax_, then are extant in _Painting_: And of a new kind of _