LECTURE XXIV. 



ASTRONOMY. 



ECLIPSES. 



IN the 20th lecture I observed that, in a period 

 somewhat shorter than a month, the moon was 

 found once in conjunction, and once in oppo- 

 sition to the sun. In conjunction, when the 

 moon is at N (Vol. i. PL XXVIII. fig. 119) 

 between the sun S, and the earth T ; and in 

 opposition, when the moon is at L, in such a 

 situation that the earth T is between it and the 

 sun. In the first case we should naturally expect 

 that the moon would hide from us the light of 

 the sun ; and in the second, that the earth would 

 prevent the sun's light from reaching the moon ; 

 and, consequently, that every such occasion 

 would produce an eclipse of one of those bodies. 

 Notwithstanding this, we find the new and full 

 moons but very seldom produce eclipses; and 

 when they happen, it is not in the same propor- 

 tions or in the same manner as you might expect 

 on a cursory view of the figure. 



If the plane of the moon's orbit were perfectly 

 coincident with that of the earth, what we have 

 been supposing would actually take place, and 



