68 



The Microscope. 



Chlorine has six colored and eleven dark lines, diagnostic are 

 four yellowish green lines and a ti'iple blue line. 



Nitrogen, a very complicated spectrum, peculiar and easily to 

 be recognized. In the part from the red to light yellow it shows 

 seventeen dark lines. At F. the spectrum shows colored lights or 

 lines. Thirteen of these may be recognized, one in blue and several 

 in violet are most brilliant. 



By the foregoing condensed statement it may be learned of how 

 the solids, the fluids and the gases may be analyzed by the spectrum 

 test; that no known substance can defy the analytical powers of this 

 test. Every known gas, metal, alkali or alkaline earth, when thus 

 acted upon by sufficient heat, gives out light, peculiar to itself, 

 producing a spectrum, difPering from any other known substance. 

 Some substances absorb all the colors of the spectrum, with the 

 exception of a single bright band, of which sodium and thallium 

 give an example; others are recognized by a spectrum of many 

 bright lines, dispersed all over the prismatic field. Of this, barium, 

 caesium and rubidium are examples. 



No. 1. John Browemg's one-prism Spectroscope. 



It is true that the degree of heat employed often modifies the 

 spectra: not indeed as to the position of the characteristic lines and 

 bands of each substance, but as to their number and brilliancy. 

 Thus thallium gives one green band when evaporated by a Bunsen 

 burner, but when it is volatilized by the far higher temperature of 

 the electric induction spark or electric arc, we see in addition several 

 bright lines in the violet. 



The same is true of lithium, calcium and others. But all these 



