258 Trees, Stars, and Birds 



H. A. Newton of Yale wondered if such a shower might 

 not have occurred many times before at intervals of 

 33 or 34 years, and by searching the records found this 

 to be true. He predicted a meteoric shower for Novem- 

 ber 13, 1866, and his prediction was verified. In No- 

 vember, 1867, another shower occurred, much feebler 

 than that of 1866, and in each following year the display 

 was fainter and fainter. In November, 1901, there was 

 a fairly good shower, but it was quite inferior to those 

 previously mentioned. 



Explanation of star showers. When a meteoric 

 shower occurs, the paths pursued by the meteors, if 

 traced back, all seem to lead to the same point. For 

 the November meteors, the point is in the constellation 

 Leo, and they are called Leonids. For the meteors 

 which fall every year about the loth of August the point 

 is in the constellation of Perseus, and they are called 

 Perseids. The meteors that fall in the same shower 

 are all moving in the same direction in an orbit about 

 the sun. The earth passes across this orbit at a certain 

 time of the year. . If the meteoric bodies are well dis- 

 tributed along this orbit, then we see them every year ; 

 if they are mostly in a swarm that takes 33 years to 

 complete a revolution, then we shall see the greatest 

 number once in 33 years, when the earth comes to the 

 orbit at the time the swarm is passing. 



Besides the Leonids and the Perseids, there are 

 meteoric showers at other dates, one about November 

 23 and another in April, besides many that are too faint 

 to attract much attention. By comparing the orbits 

 of these groups of meteors with the orbits of certain 



