lxxiii 



The various gases yield, by the spectroscope, lines equally as character- 

 istic as the metals and alkaline earths. Hydrogen, for instance, gives one 

 line of red, another of blue, and one of indigo. 



The location of the various lines of all spectra are very nearly indicated 

 by their colors. Thus the blue lines will appear in that part of the electric 

 spectrum occupied by the' blue color, the yellow lines in the yellow part, 

 and so on of the others. 



In the manufacture of Bessemer steel, the spectroscope is used to examine 

 the vapors emitted by the converter in which the moltfen metal is being 

 decarburized. By it the presence of various substances in combination 

 with the iron are detected. By the Bessemer process five tons of pig iron 

 in the converter are made into steel in twenty minutes. The carbon in 

 the iron is completely burned out by the oxygen of the atmosphere which 

 is driven in a blast through the molten mass. The heat thus generated 

 is intense, but quickly subsides after the carbon is consumed, and it is of 

 great importance that the blast be then immediately stopped. If this be 

 delayed ten seconds the mass becomes so viscid that it cannot be poured 

 from the converter. If the blast be stopped too soon, the metal will crumble 

 like cast iron when it is under the hammer. The spectroscope reveals the 

 moment when the carbon lines disappear from the spectrum, and thus 

 furnishes an exact scientific admonition, where the quickness of vision 

 was previously the sole dependence for success. When all of the carbon 

 is burned out, the exact quantity requisite for the quality of steel desired 

 is immediately returned into the converter by pouring in a certain amount 

 o f molten spiegeleisen (specular iron), the percentage o f carbon in which 

 is definitely known. It is necessary to burn all of the carbon out of the 

 iron first, as it contains too much for making steel, and it is impracticable 

 to know when exactly enough has been consumed. Hence, all must be 

 removed so as to enable the steel maker to introduce the exact percentage 

 required. 



By the spectroscope we are enabled to declare with absolute certainty 

 that several constituents of the sun. the planets, and the fixed stars, are 

 identical with those composing our earth. It has also established the 

 fact of the gaseous constitution of the nebulae and comets, and has 

 supplied us with a knowledge of celestial chemistry, such as the most 

 ardent enthusiast would scarcely have dared to anticipate. In it we have 

 a realization of the poet's dream — 



" What skillful limner e'er would choose 

 To paint the rainbow's varying hues, 

 Unless to mortal it were given 

 To dip his brush in dyes of heaven." 



With his celestial pencils charged with the glowing tints of heaven, the 

 scientific artist now creates the perfect rainbow at his will; nay, more, 

 with skillful eye he scans its wonderous texture, and reads, amidst its 

 blending shades, the sublime story of the constellations. Thus does Sci- 

 ence unfold her bow of promise to mankind. One that is rich in the assu- 

 rance of still grander truths ere long to be revealed. 



