66 BROWN : 



longitude can see some part at least of the same total eclipse. 



There are many circumstances which modify these state- 

 ments to a small extent, but the general working of the system 

 is correctly set forth. 



We have supposed our conical shadow formed, as it were, 

 by rays drawn tangent to sun and earth on the " same " side, 

 upper side, so to speak, of both, western side of both, and so 

 on. Now suppose rays drawn from upper side of sun to lower 

 side of earth, from western side of sun to eastern side of earth, 

 and so on. These rays will meet at a point between sun and 

 earth — nearer to the latter. They will form a cone pointed in 

 the direction exactly opposite to that of the umbra, or shadow, 

 previously described. The portion of the cone on the far side 

 of the earth will be in shadow, but shadow necessarily much 

 less dense than the other. 



Pcmimbra, almost shadow, therefore, — 



The moon must traverse the penumbra before reaching the 

 umbra, and may be seen to do so, the effect being that of a 

 light smoke slowly spreading over her surface. 



The moon when eclipsed in summer time appears pretty 

 low down in the south ; when in winter time, high up and 

 nearly overhead. 



If an observer were stationed at the apex of the earth's 

 shadow he would see the sun not at all. The earth would 

 eclipse the sun exactly — no more and no less. The dark side 

 of the earth would be seen as a black disk with lighter edges. 

 If the moon entered the earth's shadow she might perhaps be 

 faintly made out. 



The physical explanation of a lunar eclipse would thus 

 seem to be an elementar}^ matter enough, and that of a solar 

 eclipse is not less so. 



Once more for simplicity's sake supposing the moon to be 

 moving in the ecliptic — she comes of necessity, once in a 

 lunation, directly between the sun and the earth and her little 

 conical shadow falls in the direction of the earth. Its dimen- 



