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face. Let ABC be the circle defcribed by the revo* 
lution of a fpot. From T draw Ty’and TV touch- 
H! 
ing the circle def in f and d, and cutting ABC, in 
C and A. Join df; through S draw HSG, parallel 
to df Join SC, SA, S d. The fpots are hid be- 
hind the fun three days longer than they are vilible. 
That is, they are hid 15 days, and are feen only 12. 
The earth’s motion in 15 day is 14 0 17'. The fpots 
traverfe the like area in id. oh. 50' nearly. Hence, 
if the earth flood flill, the fpots would be hid only 
13 d. 23 h. 1 o', and their whole fidereal period being 
23d. 5h. they would be vilible 1 1 d. 5I1. 50', and 
the time of their occultation would exceed the time 
of their appearance by 2d. iyh. 20'. Hence the 
arc AC is lefs than the arc ABC, by the motion of 
2d. iyh. 2 o', that is, by 38° 52' 56". And the 
femi-circle being a mean arithmetic between A C and 
ABC, AC will be lefs than the femi-circle by half 
as much; that is, by 19° 26' 28". Hence each of 
the angles GSA, HSC is 9°43' 14T The angle 
bsd-=.d TS = 16' 1" 27"'. Therefore dS A is 
9 0 27' 12". Hence S A — 1,013767 fuch parts as > 
Sdis 1 . 
The 
