214 ASTRONOMY. 



CELESTIAL GLOBE. 



The whole starry firmament contains ninety-four constellations, and 

 is commonly described in three chief parts, as follows : 



First The zodiac, which contains twelve constellations, commonly 

 called the twelve signs of the zodiac. The zodiac is sixteen degrees 

 broad. 



Second All that space between the zodiac and the North Pole, con- 

 taining the thirty-five northern constellations. 



Third The regions south of the zodiac, containing forty-seven con- 

 stellations. 



A constellation is a convenient portion or number of stars, whichlie 

 contiguous to one another, and for the purpose of distinction is named 

 after some animal or object, which if there delineated, would nil up that 

 space as it appears to the eye. By this decision, the STARS are so 

 distinguished from one another, that any particular star may readily 

 be found in the heavens by means of a celestial globe, or map, on which 

 the constellations are so delienated, that the most remarkable stars are 

 placed in such parts of the figures as are most easily distinguished. 



The magnitude of the stars in the constellations is distinguished 

 chiefly by the letters of the Greek alphabet, that is , the first letter 

 (alplia,) is placed by the largest star in the constellation, whether of 

 the first magnitude or not ; the second letter (beta) is placed by the 

 second in lustre ; continuing in this manner to the least star in the 

 constellation ; and if there are more stars than there are letters in the 

 Greek alphabet, the letters of the common alphabet are introduced, 

 and afterwards, if necessary, the numbers 1,2, 3, 4, &c., are added. 



Some of the stars have^ besides their rays and Greek letters, also 

 names ; as Castor, &.c. 



COMETS. 



(If any thing were needed beyond the language of ridicule to dissipate 

 fear in relation to these phenomena the following able remarks from 

 Mrs. Somerville must convince the most sceptical.) 



" Only comets with retrograde motions can come into direct collision 

 with the earth, and if the momentum were great the event might be 

 fatal ; but in general the substance of comets is so rare, that it is likely 



