92 KANSAS CITY REVIEW OF SCIENCE^ 
It is, therefore, impossible to doubt that meteors are masses of matter rush- 
ing with tremendous velocity through the air. 
But this amounts to little more than a definition and does not explain the 
physical causes of the phenomena, and the questions arise ; — Whence the light 
by which we know the meteor, and whence the matter of which it is composed ? 
Now it is known that resistance to motion will always generate heat and that 
great heat is always accompanied by light. For instance, an axle or journal, if 
not properly lubricated, while rapidly rotating under great pressure, will become 
red-hot, and the reason it does not become red-hot when lubricated is that the 
oil reduces to a great extent the resistance due to friction and at the same time 
absorbs the heat generated by the resistance which it is not able to destroy. 
Moreover, we know that the atmosphere offers resistance to the passage of 
bodies proportioned to the squares of their velocities. 
Experiments in gunnery show that a fifteen-inch shot moving with a velocity 
of 1,500 feet per second encounters an atmospheric resistance of about one and 
one-half tons If such a shot could be given a meteoric velocity of thirty miles 
per second, equal in round numbers to 150,000 feet per second, the resistance 
would be increased to about 15,000 tons. The quantity of heat generated by 
such a resistance under such circumstances is unknown, but, reasoning by anal- 
ogy from the above instance of the red-Tiot axle, it seems perfectly reasonable to 
conclude that sufficient heat would be evolved to ignite and perhaps dissipate 
many rigid and practically incombustible substances. It is therefore generally 
conceded that meteoric light is caused by heat developed by the atmospheric re- 
sistance incident to the great velocity with which such bodies are known to move. 
If the meteor is composed of matter sufficiently fixed a portion of it often sur- 
vives the great heat and falls to the ground in a highly heated state. If it is 
composed of more inflammable material it is consumed and dissipated in the air, 
which explains why we may not expect a meteorite from every meteor. 
Respecting the origin of meteoric matter many theories have from time to 
time been advanced. For instance, it was supposed by some to be formed by 
the condensation of vapors of various substances in the air in a manner similar 
to that by which hailstones are produced from the vapor of water. The absurdi- 
ty of this is manifest. LaPlace, with more reason, supposed that such matter 
was cast from the Moon by volcanic action with such force as to be brought with- 
in the limits of terrestrial gravitation, and indeed considering the absence of at- 
mospheric resistance on the Moon (for that luminary has little or no atmosphere) 
and considering that the force of gravitation at the lunar surface is but one-fourth 
what it is on the earth, it is not impossible that the tremendous volcanic action pe- 
culiar to the Moon might accomplish such a result ; but, as will appear further on, 
such a supposition is incompatible with the general facts attendant upon meteoric 
phenomena. 
It happens that mechanical science is able to demonstrate that meteoric mat- 
ter is entirely foreign to the earth or Moon, thus — 
The greatest velocity with which a body, moving under the action of terres- 
