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SPECTKUM ANALYSIS. 



For chemical investigations spectrum analysis is of 

 the greatest importance, especially on account of its 

 delicacy. Each metal, or other volatile substance, gives 

 its own peculiar lines of varied colours ; and when two 

 or more different substances exist in the same vapour 

 the whole of the lines are shown in the same spectrum, 

 each in its own position, for no two metals give lines on 

 the same part of the spectrum. Further, the method is 

 so delicate that a portion of a sodium compound less 

 than the ^/ro^-oVo/oo^th P ar ^ f a gramme can be 

 detected, and compounds which were formerly supposed 

 to occur very seldom are by means of this new method 

 proved to be widely disseminated throughout the earth. 

 A still more striking proof of the value of spectrum 

 analysis lies in the fact of the recent discovery of four 

 new elementary bodies by its means, viz. the metals 

 ccesium, rubidium, thallium, and indium. 



Spectrum analysis has, however, not only been 

 employed by the chemist for the detection and discovery 

 of various substances, but also by the astronomer, for 

 investigating the constitution of the heavenly bodies. 

 If sunlight be allowed to fall upon the slit of the spec- 

 troscope, and then received on the wall, or if a slit in a 

 piece of cardboard be held against the window, and the 

 light viewed through the prism, the spectrum is not 

 essentially different from that of a candle flame, or that 

 of every solid or liquid body in a state of white heat ; 

 the violet part only will be somewhat larger. Solar 

 light contains more violet rays than that of the flame of 

 the candle or lamp ; hence when both are compared, the 

 light of the sun has a bluish, the light of the candle a 



