INORGANIC EVOLUTION II 

ledge could ever have been obtained. Concerning 
this instrument and what it is capable of revealing 
we find Professor Duncan in his very interesting 
work, “The New Knowledge,” saying,-‘‘ That the 
spectroscope will detect the millionth of a milligram 
of matter, and on that account has discovered new 
elements, commands our admiration; but when we 
find, in addition, that it will detect the nature of 
forms of matter billions of miles away and, more- 
over, that it will measure the velocities with which 
these forms of matter are moving with an absurdly 
small per cent. of possible error, we can easily 
acquiesce in the statement that it is the greatest 
instrument ever devised by the brain and hand of 
man.” 
Though spectrum analysis is a very complicated 
subject, upon which an enormous amount of work 
has been done, not many details need be referred to 
here. Points of major importance are that under 
certain conditions the different elements when 
volatilised by heat, and viewed through the spectro- 
scope, give rise to different azscontenuous or line 
spectra, and that no two elements yield precisely the 
same spectra. 
The occurrence of these distinctive line spectra is 
dependent, as Norman Lockyer says in his work on 
“Inorganic Evolution,” upon the law that “gases 
and vapours, when relatively cool, absorb those 
rays which they themselves emit when incandescent,” 
and upon the existence of the particular conditions 
above referred to that lead to the production of the 
line spectra. For the heavenly bodies these condi- 
