192 THE POPULAR SCIENCE MONTHLY 



by a meteor belonging to the swarm known as the Leonids, and ap- 

 peared at first, as is always the case, a narrow glowing streak. The 

 train soon after its appearance was sixteen to eighteen miles in length 

 and at an altitude above the earth of fifty-six miles as determined by 

 triangulation from Sidmouth and Cardiff, which are fifty miles apart. 

 It appeared lance-like for a few moments and then was seen to be 

 bending like a long floating ribbon, slowly curving about as shown in 

 sketch B. The train also gradually expanded in size. The enlargement 

 of these luminous clouds is unquestionably due to the diffusion of the 

 particles of which they are composed. A careful study of the observa- 

 tions of a large number of trains has proved conclusively that the dis- 

 tortions, such as those shown in the illustrations, are due to the different 

 wind currents that are in the atmosphere at great heights, even as far 

 distant from the earth as sixty-five miles. It is also evident that these 

 currents may vary both in direction and in velocity at different levels at 

 one time, quite similar in fact to the drifts of the atmosphere in the 

 cloud region near the surface of the earth. 



Meteor trains have been observed more frequently during the 

 periodic meteor showers than at other times, and apparently the meteors 

 which have produced the greatest number of trains are the so called 

 Leonids and Perseids. The former, it may be remembered, appear every 

 year about November 14, but produce what is known as a meteoric 

 shower every thirty-three or thirty-four years, the actual period being 



Fig. 1. Meteok Train seen at Sidmouth and Cardiff, England. Observed on 

 November 14, 1866, at 1:08 a.m. Visible until 1:20 a.m. 



