41 



SPECTEXJM ANALYSIS AND ITS APPLICATION TO 

 SCIENCE. 



By Francis Abbott, F.E.S. 



At the monthly meeting in March, 1863, I brought before 

 the Members of the Society some notes relative to the re- 

 searches and early 'investigations into the phenomena and 

 history of prismatic analysis. 



At that time the researches of Professor Kirchoff, and 

 Bunsen's appliances for the examination of colored flames, 

 were but little known. Spectroscopes were scarce, and had 

 not been introduced into the colony, consequently the only 

 way of illustrating the paper was by means of colored draw- 

 ings and some scientific apparatus. Many important dis- 

 coveries have, however, been made since that period, especi- 

 ally from the results of Spectrum Analysis applied to the 

 heavenly bodies, some of which will be rendered more 

 apparent by the few following preparatory notes on the 

 subject : — 



It is well known that the laws of radiant light and heat are 

 not only very similar but that these phenomena themselves 

 are in all probability due to the same physical cause. " This 

 analogy," says Balfour Stewart, " between light and heat as 

 regards reflection, refraction, absorption, and probably polari- 

 zation, will tend to show that radiant light and heat are only 

 variations of the same physical agent, and also that when the 

 spectrum of a luminous object has been obtained the separa- 

 tion of the different rays from each other is physicaly 

 complete." In any region, therefore, of the visible spectrum 

 the illuminating and heating effects are caused by precisely 

 the same rays. If, for instance, we take the region of the 

 spectrum near the violet, or most refrangible extremity, we 

 find that luminous and chemical effects are produced, and in 

 both cases the same rays are the active agents. 



The solar spectrum has the property of being intersected 

 by a series of dark lines, which are of great service in showing 



