190 BOOK OF NATURE LAID OPEN. 



illuminated is turned from us, by being between us 

 and the sun, she becomes totally invisible, and then 

 we have the change ; when, shortly after, the en- 

 lightened part re-appears, we call it the new moon ; 

 and when it exhibits a half-enlightened aspect, the 

 moon is said to be in her first or last quarter, accord- 

 ing to the time of her age. These appearances, with 

 all the intermediate stages, will be pretty correctly 

 represented by moving the bowl, formerly alluded 

 to, round the flame of a candle, when suspended by 

 a string, and observing in what manner the light is 

 reflected from its surface, according to the various po- 

 sitions in which it is placed in the course of its circuit, 



Eclipses. 



There are no phenomena better understood by 

 modern astronomers than the nature of eclipses; and 

 so far is there from being any thing supernatural or 

 mysterious in them, that were the orbit of the moon 

 perfectly parallel, or in the exact plane of the earth, 

 there would be an eclipse of the moon at every full, 

 and of the sun at every change ; for there is not a 

 doubt that an eclipse of the moon is occasioned by 

 the dark body of the earth happening to be in a line 

 between the sun and the moon, when the moon is 

 in a direction opposite to the sun ; while an eclipse 

 of the sun is caused by the dark body of the moon 

 passing between the earth and the sun, when she is 

 in that part of the heavens. That eclipses do not 

 more frequently happen, arises from the orbit of the 



