, and
the weight of the Lead: And in the _Fixed_ ones, the greater the _Diameter_
is, the less the Shadow or the Light is terminated; so that it is painful
enough, exactly to discern the extremities thereof. Yet 'tis certain, that
the greater the Instruments are, the surer _Astronomers_ may be: Whence it
is, the some _Astronomers_ have made use of _Obelisks_ of a vast bigness,
to take the _Altitudes_; and Signior _Cassini_, after the example of
_Egnatio Dante_, caused a hole to be made on the highest part of a Wall of
95. feet in a Church at _Bononia_, through which the beams of the Sun
falling on the Floor, mark as exactly as is possible, the height of that
Luminary.

_Fifthly_, That the Author reasons for the _Immobility of the Earth_ after
this manner. He supposes for certain, that the swiftness of the Motion of
heavy bodies doth still _increase_ in their descent; to confirm which
principle, he affirms to have experimented, That, if you let fall a Ball
into one of the Scales of a Ballance, according to the proportion of the
height, it falls from, it raiseth different weights in the other Scale. For
example, A Wooden Ball, of 11/2 ounce, falling from a height of 35 inches,
raiseth a weight of 5. ounces; from the height of 140 inches, a weight of
20 ounces; from that of 315 inches, one of 45 ounces; and from another of
560 inches, one of 80 ounces, &c. From this principle he concludes the
Earth to be at Rest; for _saith he_, if it should have a Diurnal Motion
upon its Center, Heavy Bodies being carried along with it by its motion,
would in descending describe a _Curve Line_, and, as he shews by a
_Calculus_, made by him, run equal spaces in equal times; whence it
follows, that the Celerity of their Motion would not increase in
descending, and that consequently their stroke would not be stronger, after
they had fallen thorow a longer space. {397}

_III. _ANATOME MEDULLAE SPINALIS, ET NERVORUM_ inde provenientium, _GERARDI
BLASII_, M. D._

The Author shews in this little _Tract_ a way of taking the entire _Medulla
Spinalis_, or Marrow of the Back, out of its _Theca_ or Bony Receptacle
_without Laceration_; which else happens frequently, both of the Nerves
proceeding from it, and of the Coats investing it; not to name other parts
of the same. This he affirms to have been put into practice by himself, by
a fine Saw and Wedge; which are to be dexterously used: and he produceth
accordingly in excellent Cuts, the Repres