42 Mr. G. J. Stoney [Feb. 14, 



of tlie human mind when it understands the great works of nature. 

 There is no thundering along through the heavens. All is silence and 

 peace round the planets as they swiftly glide. Bodies which sweep 

 in this way without obstruction through the depths of space, are ready 

 to yield at once the due amount of obedience to the attraction of the 

 sun. Accordingly each meteor which traverses the elliptic orbit 

 represented in the diagram, mends its pace so long as it is gliding 

 along that half of its course in which it is approaching the sun, because 

 here the sun is drawing it forwards as well as sideways ; and the 

 forward attraction increases its velocity, while the sideward attraction 

 bends its path into the oval form. The meteor takes upw^ards of 

 sixteen years to traverse this part of its orbit, and all this time its 

 velocity is on the increase. It has attained its greatest speed when it 

 reaches the point of its orbit which is closest to the sun, near to which 

 is the place where it crosses the earth's path. As it passes this point 

 its velocity is twenty-seven miles a second. The earth moves at the 

 rate of nineteen miles a second in very nearly the ojDposite direction, 

 so that if the meteor happen to strike the earth, the velocity of its 

 approach is the sum of these two numbers, or forty-six miles a second ; 

 and it is at this enormous S2)eed that it plunges into our atmosphere. 

 But if it escape the earth, and continue its course along its orbit, it 

 loses speed for the next sixteen years, until it passes the farthest part 

 of its orbit at its slowest pace, which is about a mile and a third 

 per second. In each revolution its velocity oscillates between these 

 extremes. Its orbit is so vast that it takes thirty-three years and a 

 quarter to get round it. 



Such is a good picture of the course pursued by each memter of 

 the great November swarm. There are countless myriads of meteors 

 in this mighty group, each one moving independently of the rest, each 

 one fulfilling its own destiny. They form, together, an enormous 

 stream of meteors, the dense part of which appears to be about 100,000 

 miles in width, and of immense length. The orbit along which they 

 travel was represented on the diagram by an ellipse of 207 centimeters, 

 or close upon seven feet, long — i. e. by an oval about as long and broad 

 as the hall-door of a house; and the length, breadth, position, and 

 motion of the swarm in 1865, before it reached the earth, would be 

 represented on the same scale by a thread of the finest sewing silk, 

 about a foot and a half or two feet long, creejiing inwards along the 

 orbit, the rear of the column having been between the orbits of Jupiter 

 and Saturn, and the front of it nearly as far in as the earth's orbit. 

 Tlie actual train which is thus represented was so amazingly long 

 that even moving at the rate of twenty-seven miles a second, it took 

 upwards of two years to pass the point where its path crosses the 

 earth's orbit. The earth passes this point on the morning of the 14th 

 of November in every year. The head of the dense part of the stream 

 seems to have reached the same point early in the year 1866. The 

 earth was then in a distant part of its orbit, but on the following 14th 

 of November we came round to the place where the great stream of 



