496 LECTURK XLI. 



usual to describe particular stars by their situation with respect to the imagi- 

 nary figure to which they belong, or, more commonly, at present, by the 

 letters of the Greek alphabet, which were first applied by Bayer in \60S, and 

 in addition to these, by the Roman letters, and by the numbers of particular 

 catalogues. 



There are two principal modes of representing the stars; the one by 

 delineating them on a globe, where each star occupies the spot in which 

 it would appear to an eye placed in the centre of the globe, and where the 

 situations are consequently reversed, when we look on them from without, in the 

 same manner as a word appears reversed when seen from the back of the 

 paper: the other mode is by charts, which are generally so arranged as to 

 represent the stars in positions similar to their natural ones, or as they would 

 appear on the internal concave surface of the globe. Sometimes also the 

 stars have been delineated as they would be projected on imaginary surfaces, 

 without any reference to a globe ; for instance, on the surfaces of transparent 

 cones or cylinders. The art of constructing all such projections belongs to 

 the subject of perspective. 



In describing the particular stars, it will be most convenient to begin with 

 such as never set in our climates, and we may then refer the situations of 

 others to their positions with respect to these. 



The great bear is the most conspicuous of the constellations which never 

 set; it consists of seven stars, placed like the four wheels of a waggon, and 

 its three horses, except that the horses are fixed to one of the wheels. The 

 two hind wheels are the pointers, which direct us to the pole star, in the 

 extremity of the tail of the little bear: and further on, to the constellation 

 Cassiopeia, which is situated in the milky way, where it is. nearest to the pole, 

 and which consists of several stars, nearly in the form of the letter W. The two 

 northernmost wheels of the great bear, or wain, point at the bright star 

 Capella, the goat, in Auriga. Descending along the milky way from Cas- 

 siopoia, if we go towards Capella, we come to Algenib, in Perseus; and a 

 little further from the pole we find Algol, or Medusa's head: but if we take 

 the opposite direction, we arrive at Cygnus, the swan; and beyond it, a 

 iittle out of the milky way, is the bright star Lyra. The dragon consists of 



