HOW TO OBSERVE THE HEAVENS. 



found in the first sign, and Aries in the second, and so on ; the 

 signs have, nevertheless, retained their names. 



It is therefore important that the astronomical amateur should 

 not confound the name of the sign with the name of the constella- 

 tion. The sign Aries is the first 30 of the ecliptic, while the con- 

 stellation Aries is a group of stars, at present situate between the 

 30th degree and 60th degree of the ecliptic. 



The ancients recognised, besides the twelve zodiacal constel- 

 lations, twenty-one constellations in the northern, and fifteen in 

 the southern hemisphere. The progress of stellar discovery has,, 

 however, augmented considerably these somewhat arbitrary groups 

 of stars, and the number of constellations now recognised amounts 

 to 117, of which 62 are in the northern hemisphere. 



33. Prom all that has been explained above, the student will be 

 able to appreciate the benefit to be derived from having in his pos- 

 session a collection of celestial maps. Many such have been pub- 

 lished, among which may be mentioned more particularly those 

 prepared under the superintendence of the Society for the Dif- 

 fusion of Useful Knowledge. I have found, however, one of 

 the most convenient for general purposes, "The Guide to the 

 Stars." 1 In the maps there given, will be found indications of 

 the most useful applications of the method of pointing. 



34. A celestial globe may be defined to be a working model of 

 the heavens. It is mounted like a common terrestrial globe. 

 The visible hemisphere is bounded by the horizontal circle in which 

 the globe rests. The brass circle at right angles to this, is the 

 celestial meridian. The constellations, with outlines of the ima- 

 ginary figures from which they take their names, are delineated 

 upon it. 



The globe will serve, not merely as an instrument of instruc- 

 tion, but will prove a ready and convenient aid to the amateur 

 in astronomy, superseding the necessity of many calculations 

 which are often discouraging and repulsive, however simple and 

 easy they may be to those who are accustomed to such inquiries. 

 Most of the almanacs contain tables of the principal astronomical 

 phenomena, of the places of the sun and moon, and of the prin- 

 cipal planets as well as the times when the most conspicuous stars 

 are on the meridian after sunset. These data, together with a 

 judicious use of the globe and a tolerable telescope, will enable 

 any person to extend .his acquaintance with astronomy, and even 

 to become a useful contributor to the common stock of information 

 which is now so fast increasing by the zeal and ability of private 

 observers in so many quarters of the globe. 



* Twelve Planispheres, forming a Guide to the Stars for erery Night in 

 the Year, with an Introduction. Taylor and Walton, London. 

 166 



