CHAP. III. THE PRESENT POSITION. 



IN the last chapter I referred to some of the difficulties encountered 

 by the earlier researchers in spectrum analysis. In the present one I 

 propose to pass over the history of nearly twenty years' work, with all 

 its attendant doubts and difficulties, and deal with what that work has 

 brought us, a perfect harmony between laboratory, solar and stellar 

 phenomena. 



It has been proved beyond all question that not only are both 

 fluted (or channelled-space) spectra and line spectra visible in the case 

 of most of the elements, but that many of the metallic elements with 

 which I shall have to deal in the sequel have at least two sets of lines 

 accompanying, if not resulting from, the action of widely differing 

 temperatures. 



It is important to mention that the different chemical elements 

 behave very differently in regard to the action of heat and electricity 

 upon them as we pass from the solid to the liquid and vaporous forms ; 

 tha is, the two different forms of energy are apt to behave very differ- 

 ently ; the permanent gases as opposed to the elements which generally 

 exist in the solid form is the first differentiation ; the elements of low 

 atomic weights and low melting point as opposed to the rest, is the 

 second. 



In the cases in which heat-energy can go so far, we first get an 

 increase in the free path of the molecules, and ultimately the latter are 

 made to vibrate. 



In the case of high-tension electricity, on the other hand, increase 

 of free path is scarcely involved, and hence we may have effects similar 

 to those produced by high temperature, with scarcely perceptible effects 

 of heat in the ordinary sense. 



Conversing on this subject with my friend Clifford, many years 

 ago, we came to the conclusion that the energy imparted to a molecule 

 might cause (1) an extension of free path; (2) a rotation; and (3) a 

 vibration. To get concrete images of these effects we spoke of patli- 

 heat, spins-heat, and wobble-heat. The facts seemed to show that heat 

 energy had no effect in producing line-spectra until the two first results 

 had been obtained, and, further, that in all gases and many metals it 

 had no effect in producing vibrations ; while, on the other hand, elec- 

 trical energy generally acted as if it began at the third stage and is 

 effective in the case of every chemical substance without exception. 



