58 FRAGMENTS OF SCIENCE 



the intensity of the old ones was increased. Thus, in Dr. 

 Draper's experiments, the rise of temperature that gener- 

 ated the orange, yellow, green, and blue, augmented the 

 intensity of the red. What is true of the red is true of 

 every other ray of the spectrum, visible and invisible. 

 We cannot indeed see the augmentation of intensity in 

 the region beyond the red, but we can measure it and ex- 

 press it numerically. 



With this view the following experiment was per- 

 formed: A spiral of platinum wire was surrounded by 

 a small glass globe to protect it from currents of air; 

 through an orifice in the globe the rays could pass from 

 the spiral and fall afterward upon a thermo-electric pile. 

 Placing in front of the orifice an opaque solution of 

 iodine, the platinum was gradually raised from a low, 

 dark heat to the fullest incandescence, with the follow- 

 ing results: 



Appearance Energy of 



of spiral obscure radiation 



Dark 1 



Dark, but hotter .3 



Dark, but still hotter 5 



Dark, but still hotter 10 



Feeble red 19 



Dull red 25 



Red 37 



FuUred 62 



Orange ......... 89 



Bright orange ........ 144 



Yellow 202 



White 276 



Intense white 440 



Thus the augmentation of the electric current, which 

 raises the wire from its primitive dark condition to an in- 

 tense white heat, exalts at the same time the energy of the 



