it
may appear, how much blood it really loses. To which were annext divers
others not so fit to be perused but by _Physitians_, and therefore here
omitted.

* * * * *

_A Method for Observing the _Eclipses of the Moon_, free from the Common
Inconveniencies, as it was left by the Learned Mr. _Rook_, late
_Gresham_-Professor of Geometry._

Eclipses of the Moon are observed for two principal ends; One
_Astronomical_, that by comparing Observations with Calculations, the
_Theory_ of the _Moons Motion_ may be perfected, and the _Tables_ thereof
reformed: the other, _Geographical_, that by comparing among themselves the
Observations of the same _Ecliptick Phases_, made in _divers_ places, the
_Difference_ of _Meridians_ or _Longitudes_ of those places may be
discerned.

The Knowledge of the Eclipse's Quantity and Duration, the Shadows, Curvity,
and Inclination, &c. conduce only to the former of these ends. The exact
time of the Beginning, Middle, and End of Eclipses, as also in _Total_
ones, the Beginning and End of _Total_ darkness, is useful for both of
them.

But because in Observations made by the _bare_ Eye, these times
considerably differ from those with a _Telescope_; and, because the
_Beginning_ of Eclipses, and the _End_ of _Total_ darkness, are scarce to
be observed exactly, even with Glasses (none being able clearly to
distinguish between the _True_ Shadow and _Penumbra_, unless he hath seen,
for some time before, the Line, separating them, pass along upon the
Surface of the Moon;) and lastly, because in small {389} _Partial_
Eclipses, the Beginning and End, and in _Total_ ones of short continuance
in the Shadow, the Beginning and End of _Total_ darkness, are unfit for
nice Observations, by reason of the slow change of _Apparences_, which the
_Oblique_ Motion of the Shadow then causeth. For these reasons I shall
propound a _Method_ peculiarly design'd for the Accomplishment of the
_Geographical_ end in Observing Lunar Eclipses, free (as far as is
possible) from all the mentioned Inconveniences.

For, _First_, It shall not be practicable without a Telescope. _Secondly_,
The Observer shall alwayes have opportunity before his principal
Observation, to note the Distinction between the _True Shadow_ and the
_Penumbra_. And, _Thirdly_, It shall be applicable to those Seasons of the
Eclipse, when there is the suddenest Alteration in the _Apparences_.

To satisfie all which intents,