508 PRESENT FUNDAMENTAL CONCEPTIONS OF PHYSICS. 



plains the fundamental phenomena of the radiation of light and heat. 

 The ultimate particles of an incandescent metal or the flame of a lamp 

 or any similar source of heat and light execute extremely rapid oscilla- 

 tions, whose kinetic energy is imparted to the atoms of the surrounding 

 aether in a similar manner to that effected by resounding bodies on 

 the surrounding air. Just as the latter vibrates and transmits tones, 

 so also does the oscillating aether transmit light. While however in 

 the transmission of sound through the air the particles of the latter 

 vibrate in the direction of the sound rays, it is most probable, in 

 accordance with certain phenomena, that in the transmission of light the 

 oscillations of the sether atoms take place in a direction perpendicular 

 to the rays of light. The hypothesis is that the elasticity of the aether 

 permits the displacement in a lateral direction to the rays much more 

 easily than in their direction, or longitudinally. 



Colorless light, as we know, may be reduced to the primary colors of 

 the rainbow by means of a glass prism. These variously colored compo- 

 nents of the colorless light are virtually the same in regard to it, that the 

 different low and high tones are with reference to sound, and they are 

 transmitted by the aether in a manner similar to that of the propagation 

 of the several tones of sound by the air. Mathematical optics teaches 

 that the difference in optical tones — i. e. the difference in the spectral 

 tints — like tbe difference in acoustic tones, is owing to the unequal length 

 of the oscillating aether waves, or to the unequal number of oscillations 

 of the constituent atoms. In the different length of the waves of the 

 various spectral colors we see why the variously colored component rays 

 of the colorless light are, by refraction, diverted from each other and 

 scattered in a spectrum in a fan -like shape. 



The more rapidly the aether atoms oscillate, or the shorter the wave, 

 the nearer to the violet-colored limit of the spectrum will the correspond- 

 ing tint be located. The longest aether waves are on the red, the short- 

 est on the violet-colored end of the spectrum ; between the two occur the 

 aether waves of medium length. The rays of the spectrum produce three 

 kinds of effects, by means of their kinetic energy, accordingly as they 

 fall on different bodies. In the region of the red rays and in the invisi- 

 ble space beyond them a heating of bodies placed there predominates; 

 therefore an increase of the molecular energy takes place ; the rays from 

 red to violet (among them the yellow ones, particularly) act principally 

 on the nerve ends of the retina of the eye and excite the optic sensibility; 

 the blue ones — the violet ones, particularly, and the invisible rays beyond 

 the violet — produce chemical changes as the shorter waves of the oscil- 

 lating aether pass over to the sether between the atoms of a molecule, 

 and thereby cause separations as well as a different grouping of the 

 atoms into new molecules, dissimilar to those previously existing.* 



* [The researches oi' the <'1<1<t Draper tend to discredit entirely the generally 

 received view lure stated, that the calorific, optical, and aclinic effects of the solar 

 radiation occupy different positions in the spectrum, or have different refrangihilities. 



