FACTS AND FANCY CONCERNING COMETS. 31 



we shall be surprised to find that the velocity of impact on the sun, by a mass 

 falhng that distance, is only one-fourth of an inch less per second than if it came 

 from an infinite distance, or, what is the same thing, had been falling forever ! 

 Surprise will wane, however, when it is remembered that gravity varies as dis- 

 tance squared inversely, and at an infinite distance must be infinitely weak, and 

 the motion it can impart infinitely slow. Hence, 10,000,000,000,000 miles has 

 nearly the same relations to solar gravity that infinite space has. Drawing near- 

 er the sun, let us halt at the orbit of Neptune, 2,780,000,000 miles distant, and 

 again apply the formula ; when behold, if a mass fall through the distance of 

 Neptune, it will reach the sun with only 155 feet per second less velocity than 

 if it had been falling throughout all duration of time. Still nearer, we come to 

 the orbit of the earth, 92,000,000 miles from the sun's center, and, again com- 

 puting, find that final velocity of impact on the solar globe of matter from terres- 

 tial distance, would be but 2,411 feet per second less than if it arrived from in- 

 finite space. By the use of this important number, 2,008,908, it can at once be 

 told what is the velocity of any cosmical mass at any point in its flight to the sun. 

 Calculating for the earth's distance, it is found that a body passing our world on 

 its way to the sun has a velocity of twenty-six miles per second, which is the 

 greatest velocity with which anything can strike the earth. Arriving at the orbit 

 of Mercury and again calculating, we find that a mass beginning to fall from that 

 distance, 36,000,000 miles, will impinge on the sun with a rate of motion only 

 5,706 feet per second less than if it had been falling forever. Hence, terminal 

 velocities lies within small limits of variation. Here is a table of velocities 

 in feet per second of bodies making impact on the sun, falling different distances: 



From infinite distance, maximum 2,008,908 



From Neptune 2,008,753 



From Mars 2,007,361 



From the Earth 2,006,497 



From Mercury 2,003,202 



From 436,000 miles, minimum 1,420,513 



\i is seen that interstellar matter, whether colliding with the sun from infinite 

 fall, or from Mercury, has 5,706 feet, a trifle over i mile per second difference in 

 final velocity, variation being withiij the limits of 1-380 of the whole. The rate 

 of the motion in the last line of the table is that attained by a mass falling on 

 the sun from a distance equal to the solar radius, 430,000 miles, as we can not 

 imagine that any cosmic matter will begin to fall from a less distance. There- 

 fore, the least velocity of impact is 1,420,513 feet, or 269 miles, per second, and 

 this least motion multiplied by 1.414213 equals 2,008,908 the greatest, hence 

 the maximum and minimum velocities are to each other as i is to the square root 

 of 2, or as I is to 1.414213, 



If we square 1,420,513 and multiply the reciprocal of the square of Joule's 

 equivalent, as above, we obtain the least heat possible, or 40,577,090° F. What 

 astonishing results are brought to light by these researches. Incredible intensity 



