INTRODUCTION. Vll. 



DIVISIONS OF TIME. 



But we must now return to the earth and its 

 atmosphere, and to those phenomena generated by 

 its revolution round its axis and orbit, and the 

 consequent division of time to which the natural 

 and artificial calendar relate. 



The Year Annus is computed by the circuit of 

 the earth from one point of the orbit, till it comes 

 to the same point again ; and the Christian year 

 is computed from the place of the earth, about the 

 time when Christ was born, and is now fixed, 

 by consent, for the octave of the nativity, or first 

 of January, according to the calendar established 

 by St. Gregory : that is about 10 ° from the 

 winter solstice. The orbit orhita solis is divided 

 artificially into 360 degrees, and as the earth is 

 ratlier more than 365 days in going round it^ so 

 it may be said to move somewhat less than one 

 degree each day, or about 30° each month. But 

 it will be asked what are days and months ? 



A Day, dies, maybe thus explained: the earth, 

 besides its circuit round the sun, called its orbit, 

 revolves round its own poles, turning in succession 

 every part of its surface towards the sun, and in 

 turn, away from it, thus generating the alteration 

 of daylight and of darkness. This occupies 

 twentyfour hours of time, so that the ash'ono- 



