METEORS AND COMETS. 



491 



apparently on these occasions, and are called after their names as Leonides, 

 from Leo, in the November displays. 



The star-showers at times attain the dimensions of a very beauti- 

 ful display of rockets. Millions of them rush round the sun ; and when, as 



occasionally happens, our earth 

 comes near them, we have (as in 

 1866) a grand display of celestial 

 " fireworks." But the individuals 

 composing the mass, of falling stars 

 are very small. These meteors are 

 very much like the comets we last 

 year had an example of, and it 

 has been lately suggested that there 

 is a great degree of affinity between 

 the comets and the meteors; in 

 fact, that a comet is merely an 

 aggregation of meteors. They 

 have been supposed to be bodies of 

 burning gas. Their mass is very great, and their brilliant tails are many 

 millions of miles in extent. 



Comets are thus distinguished by their tails, and differ very much in 

 their orbits from the planets. The latter are direct in their wanderings, but 

 comets are most irregular and eccentric. The name bestowed upon comets 

 is from the Greek Kome, hair; for when the comet recedes from the sun the 

 " tail " may be said to come out of the head, and appear as a hair in front, 

 so to speak. But though all comets have tails, there are many luminous 

 bodies (classed with comets) which have no tails. 



The comet which created the most excitement was H alley's in 1456, 



i- jg. 530. btar shower. 



ys Comet. 



of which we append an illustration (fig. 537). A comet had been observed 

 in 1607, and Halley made a calculation that it would reappear in 1757. 



