22 Astronomy. [Lecture 24. 



quently in a place,fg, where the shadow is nar- 

 rower. 



When the moon is even totally eclipsed, she 

 does not cease to be visible, for it is only the 

 shadow of the earth which is cast upon her. She 

 appears of a copper colour, or like a heated iron 

 half extinguished. This effect arises from the 

 scattered rays of light from the moon, which are 

 refracted by the terrestrial atmosphere, and, 

 crossing each other, afford a faint picture of the 

 moon. This light is feeble, because it is small 

 in quantity, and it is of a reddish colour, be- 

 cause only the red rays can penetrate our at- 

 mosphere in these circumstances. This is more 

 obscure in proportion as the moon is nearer the 

 earth at the time of the eclipse : there have even 

 been eclipses when the moon has totally disap- 

 peared, but this is a rare phenomenon. 



An eclipse of the sun can only take place 

 when the moon is in conjunction with the sun, 

 and when she is in one of her nodes, or very 

 near it. Suppose the line EE (fig. 8) to be a 

 portion of the ecliptic, and LL a portion of the 

 orbit of the moon, cutting the ecliptic in the 

 point N, at an angle of a little more than five 

 degrees. Then, if in the moment of her con- 

 junction the moon is found in the point F of her 

 orbit, she will be too far from her node to inter- 

 cept the sun's light, and cause an eclipse. But 

 if she is in the point G, having less latitude, she 

 will hide a portion of the disc of the sun ; and 



