System of the Universe. $65 



The inhabitants of this sphere are those who live under 

 the equinoctial line, and have their days and nights 

 always equal, viz. twelve hours each ; because not only 

 the equator but also all the parallels of latitude are cut 

 into two equal parts by the horizon. And therefore, as 

 the sun's diurnal arches are equal to the nocturnal, each 

 day must be equal to the night, viz. twelve hours each. 

 The sun rises and sets nearly in a vertical direction. 

 He comes to the meridian \vith the same degree of the 

 equator with which he rose ; and hence there can be no 

 ascensional difference. He i$ half a year on one side of 

 their zenith, and as much on the other ; passing over 

 their zenith but twice a year, viz. at the equinoxes. 



An oblique sphere is so called because in it the equator 

 cuts the horizon obliquely. This position of the globe is 

 common to all the inhabitants of the earth, except those 

 who are situated under the poles, and under the equinoc- 

 tial. The properties of this sphere are as follow : the 

 pole is elevated to any degree less than ninety, the axis of 

 the earth always making an acute angle with the horizon. 

 A ' . the parallels to the equator cut the horizon obliquely, 

 nnking the diurnal greater or less than the nocturnal 

 arches j and consequently producing an inequality in the 

 days and nights, which are never equal but when the 

 sun is in aries and libra, which happens in March and 

 September, when he moves in the equator, making equal 

 days to alF the inhabitants of the earth, except those 

 under the poles. The inhabitants of this sphere, who live 

 without the tropics, never have the sun in their zenith, 

 but under the tropics he is vertical once, and between 

 the tropics and the equator twice, every year. The stars 

 rise and set obliquely in this position ; and the nearer the 

 observer is situated to the equator, the greater number 

 of them will be visible. The length of the twilight is 

 longer or shorter in this position, according as the lati- 

 tude is greater or less. 



VOL. I. N 



