C 3°3 ) 
To conclude, I will propofe a Method of obferving 
the Figure of the Shadow of the Earth in Lunar Eciipfes, 
whereby the Difference between the Diameters in the 
oblong fpheroidical Figure, if there be fuch an one as 
Monf. Caffini affirms (viz. of 96 to 95*) may be difco- 
ver’d. 
Let P ,/E P iE * reprefent the Earth, feen from the Sun 
at the Time of the Summer Soldice } it is evident, that 
the fame Figure will exprefs the Sedion of the Earth’s 
Shadow at the Moon’s Didance, as feen from the Earth. 
If EE reprefents the Ecliptick, iE /£ will be the fhorteft 
Diameter of the Sedion ; and if L L be taken for the 
Moon’s Way, in a total and central Eclipfe of the Moon, 
by obferving the Time which is fpent in the Paffage of 
the Center of the Moon, thro’ the Shadow, and reducing 
that Time to Seconds of a Degree of a great Circle of the 
Heavens, we (hall have the lead Diameter of the Sha- 
dow. 
Again, let the fame Letters f reprefent the fameThings, 
only here the Section of the Shadow is fuch, as the 
Earth will cad at the ^Equinox, and the Eclipfe of the 
Moon is here fuppofed partial, its Center jud touching 
the Shadow. When the Moon’s Center is got to c y if 
the Latitude of its Center or its Didance from the E- 
cliptick be obferv’d,we diall have the Length c C nearly 
equal to the longed Semi-diameter of the Shadow. 
Now, comparing cC* in this Figure to L C * in the 
former (the Difference between c C and C P (Fig. 7.) 
and between CL and C ftL(Fig. 6.) not being worth 
notice) they ought to be to one another, as 9 6 to 95*, 
which in fuch a Shadow will give a Difference of a- 
bout 25" at a Medium, fenfible enough to be obferved, 
notwithdanding the Tenumbra. If therefore thofe A- 
Fig. VI. t Fig. VII. 
U 
Fig. VII. * Fig, VI 
U Z 
dronoiner9 
