PROGRESS OF METEORIC ASTRONOMY IN AMERICA. 309 
it; and, further, if the conditions as regards rest are the 
same, the spectrum should be the same, and we ought to 
find this line in the spectrum of comets when the swarm 
most approaches the undisturbed nebulous condition, the 
number of collisions being at or near a minimum— i. e., when 
the comet is near aphelion the fluting should be visible 
alone.” 
After citing the results of the spectroscopic observations 
of several comets, the author remarks: “ This spectroscopic 
evidence is of the strongest, but it does not stand alone. 
Comets at aphelion present the telescopic appearance, for 
the most part, of globular nebuke.” 
The comprehensive theory set forth in the quotations just 
cited assumes that the aurorse, nebulae, meteorites, comets, 
and most of the stars all have a common origin, and that 
all the multifarious teloscopic and spectroscopic phenomena 
exhibited by these bodies are due to the varying velocities 
of the collisions between the meteoric particles and masses 
of which in some form all these bodies are composed. 
We are told that meteorites at a low temperature, present 
in the spectum a certain line, at 558, due to manganese, and 
also that this line appears in the nebulse, the aurora, and in 
comets at considerable distances from perihelion. Hence 
the identity of all these bodies is inferred and the foundation 
of the theory is laid. 
Meteorites are subjected to laboratory experiments in tubes 
in which the temperature is gradually raised to a high 
degree and the varying spectra is noted. Spectroscopic ob¬ 
servations of nebulse, comets, and stars are then compiled 
and classified, until the several groups are so arranged that 
they present nearly the same sequence of spectra that have 
been derived from meteoric matter at increasing temperatures 
in the experiments. 
The theory is then extended and we are given to under¬ 
stand that when, in the case of nebulse and stars greater 
activity of collisions occur, or w T hen a comet approaches the 
sun, the same phenomena appear and in the same order. 
