System oftlie Universe. 263 



third is on the back of the Centaur* which is too 



x * 



far south to be seen in Britain. A fourth, of a 

 smaller size, is before Antinous's right foot, having 

 a star in it, which makes it appear more bright. 

 A fifth is in the constellation of Hercules, be- 

 tween the stars and TJ, which spot, though but 

 small, is visible to the naked eye, if the sky is 

 clear, and the Moon absent. It is also found 

 that several of the stars, which appear single to 

 the naked eye, are double, triple, or even qua- 

 druple, when viewed through a good telescope. 

 Dr. Herschell and other astronomers have classi- 

 fied these. 



Dr. Herschell has discovered other appear- 

 ances in the heavens, which he calls nebulae or 

 cloudy stars. They are stars surrounded by a 

 faint luminous substance of a considerable extent. 

 What the nature of this substance may be we 

 cannot easily conjecture, but the phaenomenon is 

 certainly very curious and interesting *. 



* Before I proceed any further in explaining the solar 

 system, it seems proper to make the student acquainted 

 with the principal words and phrases which are appro- 

 priated to this science. 



The poles are the extremities of the axis on which the 

 globe turns. 



The globe or sphere is divided into two equal halves 

 or hemispheres by one great circle, perpendicular to the 

 axis, which for that reason is called the equator or equi- 

 noctial. 



The sensible horizon is a circle which separates the 

 visible from the invisible hemisphere, or that which is 



