394 LECTURE XLI. 



brilliant than any other star or planet, and changing perpetually into all 

 the colours of the rainbow, except when it was near the horizon ; it re- 

 mained visible for about a year. Many other new stars have also been 

 observed at different times.* 



For describing the particular fixed stars according to their relative situ- 

 ations, it is necessary to consider them as they are visible to the inhabitants 

 of the earth. They have been divided, for the sake of convenience, into 

 parcels, making up imaginary forms, denominated constellations. This 

 division is of very remote antiquity, and though it may be useless, and some- 

 times even inconvenient, for the purposes of minute observation, yet ( for 

 a general recollection of the great features of the heavens, these arbitrary 

 names and associations cannot but greatly assist the memory. It is also 

 usual to describe particular stars by their situation with respec^'to the 

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

 the letters of the Greek alphabet, which were first applied by Bayert in 

 1603, 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. Some- 

 times 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 situa- 

 tions 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 Cassiopeia, 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 little out of the milky way, is the bright star 



* See Ph. Tr. 1715, p. 354 ; 1780, p. 338 ; 1786, p. 189 ; 1792, p. 24 ; 1795,, 

 p. 166; 1796, p. 452. 



f Baieri Uranometria, Augsb. 1603. 



