inued to be pressed in that same
_Inclination_, according as the Glass is worn. All which particulars, he
conceives to be very hard in the practice; not to mention, that the weight
of the Glass, that should be inclined to the _Horizon_, as 'tis represented
by Mr. _Hook_, would make it slide upon the _Cement_, and so {60} change
the _Center_; and that the Glass is not pressed at the same time by the
_Ring_ but in one part on the side, _vid._ about a fourth; and that the
parts of the Glass are not equally worn away, &c. What then, _saith he_,
would becom of a Glass of 10000 feet, which, according to the said Table,
would have more than four feet, or four feet and nine inches, or five feet,
seven inches _Aperture_, and of which the _Ring_, though it were two feet
nine inches, would have but one minut of _Inclination_, and the Glass of 5
feet _Aperture_ would have but 4 minuts, and the curvity of it would be
less than the eight part of a Line.

But, _saith he_, let us consider, only a Glass of 300 foot, to see, what is
to be hoped of that, and to know at least the difficulty, to be met with in
making a Glass only of that Length. A Glass then of 300 foot, according to
his Table, must have more than 8 inches _Aperture_, which maketh but 16
minuts of its _Circle_, and it should have more than 11 inches, if it be an
excellent one. If Mr. _Hook_ (adds he) did use but his _Ring_ of 6 inches,
which he would use from twelve to an hundred foot Glass, the _Inclination_,
which the _Axis_, or _Mandril_, that bears his Glass, should have, should
be but 16 minuts, and the _Curvity_ of the Glass would be less than the
eighth part of a Line, and if he should use a bigger, the _Inclination_
would be proportionable.

Whence it may be judged (continues he) that we are yet very far from seeing
_Animals &c._ in the _Moon_, as Monsieur _Des Cartes_ gave hope, and Mr.
_Hook_ despairs not of. For, he believes by what he knows of _Telescopes_,
that we are not to look for any above 300 or 400 foot at most; and he
fears, that neither _Matter_ nor _Art_ will go even so far.

When therefore (_saith he_) a Glass of 300 foot should bear an Eye-glass of
6 inches (which would appear wonderful) it would magnifie but 600. times in
_Diameter_, that is, 360000 times in _Surface_: but suppose, that such
could be made, as would magnifie a 1000 times in _Diameter_, and 1000000.
of times in _Surface_, admitting there were but 60000 leagues from the
_Earth_ to the