40 FRAGMENTS OF SCIENCE. 



Appearance Energy of 



of spiral. obscure rays. 



Dark '. 1 



Dark 6 



Faint red 10 



Dull red 13 



Red 18 



Full red 27 



Orange 60 



Yellow 93 



White 122 



Here, as in the former case, the dark and bright radi- 

 ations reached their maximum together; as the one aug- 

 mented, the other augmented, until at last the energy of 

 the obscure rays of the particular refrangibility here chosen 

 became 122 times what it was at first. To reach a white 

 heat the wire has to pass through all the stages of invisible 

 radiation, but in its most brilliant condition it embraces, 

 in an intensified form, the rays of all those stages. 



And thus it is with all other kinds of matter, as far as 

 they have hitherto been examined. Coke, whether brought 

 to a white heat by the electric current, or by the oxyhydro- 

 gen jet, pours out invisible rays with augmented energy, as 

 its light is increased. The same is true of lime, bricks, 

 and other substances. It is true of all metals which are 

 capable of being heated to incandescence. It also holds 

 good for phosphorus burning in oxygen. Every gush of 

 dazzling light has associated with it a gush of invisible 

 radiant heat, which far transcends the light in energy. 

 This condition of things applies to all bodies capable of 

 being raised to a white heat, either in the solid or the mol- 

 ten condition. It would doubtless also apply to the lumi- 

 nous fogs formed by the condensation of incandescent 

 vapors. In such cases when the curve representing the 

 radiant energy of the body is constructed, the obscure 

 radiation towers upward like a mountain, the luminous 

 radiation resembling a mere " spur " at its base. From 

 the very brightness of the light of some of the fixed stars 

 we may infer the intensity of that dark radiation, which is 

 the precursor and inseparable associate of their luminous 

 rays. 



We thus find the luminous radiation appearing when the 

 radiant body has attained a certain temperature; or, in 

 other words, when the vibrating atoms of the body have 



