POPULAR SCIENCE 259 



have resulted in absorption or wave interference * in one place 

 and not in the rest of the spectrum, which still vibrates with arti- 

 ficial light, while in the latter, combustion shows only the vibra- 

 tions, the same vibrations that in the latter case were invisible 

 owing to interference — ^vibrations proper to the element itself, 

 and not that of artificial light. The absorption, then, though 

 it represents destruction from interference as we apply it experi- 

 mentally, is actually due to a construction in the assortment of 

 forces in the element itself, forces manifested to us only in its 

 emission spectrum. The more highly assorted these forces are 

 in the element, the greater is the absorption spectrum ; the 

 simpler the element, the more continuous is its spectrum. If we 

 look at a red object through blue glasses, we see it black, like 

 the absorption band of an element ; if we view it as it is, we see 

 it red, for it emits only the red rays, like the emission spectrum 

 of our standard element ; the rest it has absorbed. This inter- 

 ference in radiation has only one possible explanation — namely, 

 that the object itself possesses the inherent vibrations that 

 enable it to destroy some of the applied light vibrations ; that 

 is, a black object possesses certain inherent vibrations in its 

 assorted natural structure that are capable of causing complete 

 interference or absorption of all the vibrations of white light. 

 Such an assortment of forces in the element is naturally per- 

 manent — as permanent as the atomic construction of the element 

 and as indestructible. Were a gradual retrogression to the 

 primitive continuous spectrum theoretically possible, it would 

 necessarily be only towards a fresh beginning to the rhythm of 

 a complicated cycle. 



Our further examination of Light reveals certain other 

 qualities in its nature that confirm its analogy with electric 

 phenomena : as magnetism represents an overtone of electricity, 

 so does the polariscope tell us that there are some vibrations 

 in white light executed in other planes than that of polarised 

 light, the simplest form of light vibration. This is another 

 aspect of light vibration — a super-overtone independent of, and 

 relative to, colour vibration : an overtone relative to white light. 



In considering this quality relative to substances, we must 

 bear in mind that the more highly developed the substance, the 

 less primitive light phenomena it possesses, in a sense that, here 

 as elsewhere, complexity seems to be the aim of Nature ; that 

 is, that the properties of a molecular substance which is said to 

 be " optically active," when both aspects of the substance's 



* The analogy between Sound and Light vibrations is more complete as 

 we realise that two sound wave lengths, reaching the ear by two different 

 paths, will cause complete destruction or silence, if the paths of the two 

 vibrations differ in length by half a wave length ; similarly complete mutual 

 interference between two rays of light will cause destruction or darkness. 



