Eclipses. 21 



orbit, she will be too far from her node, which 

 is in N, and will have too much latitude to be 

 able to reach the shadow. But if she be found 

 in the point G, having less latitude, a portion of 

 her disc will be plunged in the shadow. There 

 will then be a partial eclipse, and if the moon be 

 still nearer to her node, as at the point H, the 

 greater the obscuration will necessarily be. 



In fine, if in the moment of opposition the 

 moon be found precisely in her node N, the 

 eclipse will not only be total, but central, and 

 even will remain so for some time; for the centre 

 of the moon coincides with the axis of the conical 

 shadow formed by the earth ; and this conical 

 shadow DEC (fig. 7) occupying, in the orbit of 

 the moon, a space FG, orfg, greater than the 

 diameter of the moon L or M, it shades this 

 planet for a time proportioned to the length by 

 which the diameter of the shadow exceeds that 

 of the moon, and this it is that causes the conti- 

 nuance of this planet in the shadow. The moon 

 remains thus obscured the longest time when the 

 sun S is in apoge, and the moon L in perige ; 

 for then the conical shadow is the greatest that 

 can be ; and the moon being in the point L of 

 her orbit, which is the nearest the earth, is 

 found also traversing the shadow in the place 

 where this shadow has the greatest diameter, 

 FG, that the moon can reach ; whereas, when 

 the moon M is in apoge, she traverses the co- 

 nical shadow nearer the summit C, and conse- 



