Spectrum Analysis, name given to the method of determining the composition of a body by means of the spectrum of light which it gives forth or passes through it, founded on the principle that a substance powerfully absorbs exactly the rays it radiates, and every substance has its own absorbing powers; or it may be defined the method of distinguishing different kinds of matter by their properties in relation to light.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Spectrum * Speculative, The