Lesson xiv.] ECLIPSES. 63 



a complete eclipse to all the inhabitants residing 

 within that track; but no where else ; for in the 

 large space around, within the limits of the fainter 

 shade called the penumbra, the eclipse will only 

 be partial. 



It will not be difficult to understand that solar 

 eclipses can only happen about the time of New 

 Moon, when the Moon is in conjunction with the 

 Sun, In the nodes, when the Moon has no visible 

 latitude, the eclipses are total : out cf the nodes, 

 but near them, the eclipses are partial : the limits 

 are about 17 degrees on each side the nodes: 

 but much also depends upon the Moon's latitude, 

 for it must in these cases be always less than the 

 apparent semi- diameters of the Sun and Moon 

 added together. 



Some circumstances of solar eclipses, as de- 

 scribed by the very ingenious author before-men- 

 tioned in this Lesson, are, 1. That none of them 

 are universal ; that is, none of them are seen 

 throughout the whole hemisphere which the Sim 

 is then above : the Moon's disc being much too 

 little, and much too near the Earth, to hide the 

 Sun from the whole disc of the Earth. Commonly 

 the Moon's dark shadow covers only a spot on the 

 Earth's surface, about 180 miles broad, when the 

 Sun's distance is greatest, and the Moon's least. 

 But her partial shadow or penumbra, may thea 

 cover a circular space of 4900 mites in diameter, 

 within which the Sun is more or less eclipsed as the 

 places are nearer to or farther from the centre of 

 the penumbra. In this case the axis of the shade 



passe 



