METEORS. 93 
trial gravitation alone could possibly strike the earth, would evidently be attained 
by letting the body fall from an infinite distance — and it is demonstrated by a 
well-known theorem in dynamics that under such circumstances a body would 
strike the earth with a velocity of about seven miles per second ; but we have 
seen that meteors move with velocities varying from seventeen to thirty-six miles 
per second, so that they must have a velocity not due to the earth; which is but 
another way of stating that they must have a planetary motion. 
Therefore meteors are cosmical bodies ; that is bodies having their origin in 
the same general cause which produced the Sun, Moon and stars, so that they 
may be regarded as minute planets or comets moving around the Sun, obeying 
the same laws and controlled by the same forces which order the motions of the 
most gigantic planet of our system. 
When we consider that between the orbits of Mars and Jupiter there are more 
than two hundred small planets, varying in size from two hundred and fifty to 
sixteen miles in diameter, and that others zxt being discovered every year, it 
seems entirely reasonable to conclude, even without reference to meteoric phe- 
nomena, that there are myriads of such bodies belonging to the solar system so 
very small that they can never be detected. 
And meteoric phenomena show that the orbital motions and positions of 
these small bodies are such as occasionally to bring them within the dominion of 
terrestrial gravitation, whereupon they are drawn from their orbits toward the 
earth with increasing velocity, and striking the atmosphere burst into flame from 
the causes given above. 
However satisfactory it may seem in explaining the ordinary meteor, which 
may be seen on almost any clear night, to flash like a rocket across the sky, it 
would be spreading the above reasoning over too much surface to extend it to 
those periodical phenomena, called meteoric showers, which make it appear as 
if all the stars in the heavens were being precipitated upon us. 
It having been observed that all planets revolve around the Sun in the same 
direction and nearly in the same plane, and that the Sun himself rotates in the 
same direction about an axis nearly perpendicular to the mean position of the 
planes of the planetary orbits, the suspicion arose that this could not be the re- 
sult of chance, and that therefore the mechanism of the solar system must derive 
its motions from a single physical cause — and indeed it has been demonstrated 
that the probability for a single cause for 228 planets moving in the same direc- 
tion around the Sun is i — \.2ni in which i represents certainty. The fraction 1328 
when developed would be represented by i divided by a number of sixty-nine 
figures, so that the value of the fraction would be almost nothing, which shows it 
to be a practical certainty that such motions are the result of law and not chance. 
The attempts to discover this law directed somewhat by the suspected exist- 
ence of gaseous nebulae, culminated in the nebular hypothesis, which resting as 
it does upon such a high degree of probability, conforming so entirely to natural 
law, and explaining so many phenomena entirely inexplicable on any other theory, 
