THE USE OF THE CELESTIAL GLOBES. 333 



one another (suppose 10 degrees) beginning at Aries 

 or at Libra, where these two circles intersect each ^^-^/ 

 other. Then turn the globe round its axis, and you will 

 see that all the marks in the first quadrant of the eclip- 

 tic, or from the beginning of Aries to the beginning of 

 Cancer, come sooner to the brazen meridian than their 

 corresponding marks do on the equator : those in the 

 second quadrant, or from the beginning of Cancer to the 

 beginning of Libra, come later ; those in the third qua- 

 drant, from Libra to Capricorn, sooner ; and those in the 

 fourth, from Capricorn to Aries, later. But those at the 

 beginning of each quadrant come to the meridian at the 

 same time with their corresponding marks on the equator. 



Therefore, whilst the sun is in the first and third 

 quadrants of the ecliptic, he comes sooner to the meri- 

 dian every day than he would do if he kept in the equa- 

 tor ; and consequently he is faster than a well regulated 

 clock, which always keeps equable or equatorial time : 

 and whilst he is in the second and fourth quadrants, ho 

 comes later to the meridian every day than he would do 

 if he kept in the equator ; and is therefore slower than 

 the clock. But at the beginning of each quadrant, the 

 sun and clock are equal. 



And thus, if the sun moved equably in the ecliptic, 

 he would be equal with the clock ou four days of the 

 year, which would have equal intervals of time between 

 them. But as he moves faster at some times than at 

 others (being eight days longer in the northern half of 

 the ecliptic than in the southern) this will cause a second 

 inequality ; which, combined with the former, arising 

 from the obliquity of the ecliptic to the equator, makes 

 up that difference, which is shewn by the common equa- 

 tion tables to be between good clocks and true sun- 

 dials. 



The Description and Use of the Armillary Sphere. 

 Whoever has seen a common armillary sphere, (plate 4, 



