PROGRESS OF METEORIC ASTRONOMY IN AMERICA. 293 
there is no essential difference as to astronomical character. 
In all their characteristic phenomena there is a regular grada¬ 
tion of meteors from one end of the line to the other. They 
differ in bigness, but in their astronomical relations we can¬ 
not divide them into groups. They are all similar members 
of the solar system. In proof of these statements we cite 
some of the points in which the large and small meteors are 
alike and unlike: 
1st. They are all solid bodies. It is doubtful whether a 
small gaseous mass could exist permanently as a separate 
body in the solar system. A liquid would probably freeze 
and become solid. In any case, neither a gas nor a liquid 
could for an instant sustain the resisting pressure which a 
meteor is subjected to in the air, much less could it travel 
against it with the velocity observed in ordinary meteor 
flights. In short, every shooting-star must be a solid body. 
2d. The large meteors and the small ones are seen at about 
the same height from the earth’s surface. The air is a shield 
to protect the earth from an otherwise intolerable bombard¬ 
ing by these meteors. Some of the larger masses penetrate 
this shield, or, at least, are not melted before their final explo¬ 
sion, when the fragments, their velocity all gone, fall quietly 
to the ground. The small ones burn up altogether or are 
scattered into dust. 
3d. The velocities of the large and the small meteors agree, 
and, though they are never measured directly very exactly, we 
are sure that in general they are more than two and less than 
forty miles per second. Velocities of from ten to forty miles 
per second imply that these masses are bodies that move 
about the sun as a^center or else move through space. These 
velocities, as well as other facts, are utterly inconsistent with 
a permanent motion of such bodies about the earth or with 
a terrestrial or a lunar origin. 
4th. The motions of the large and small meteors as they 
cross the sky have no special relations to the ecliptic. If 
either kind had special relations to the planets, in their origin 
or in their motions, we should have reason to expect them, 
