168 



THE MECHANISM OF LIFE 



of gas is suddenly produced (the substance of the dynamite now 

 occupying an enormously greater space than it did before the 

 explosion). This sudden production of gas sets up a sound wave 

 in the atmosphere that is, a series of condensations and 

 rarefactions of the air, which, again, means simply a series of 

 displacements of the molecules of nitrogen and oxygen in the 

 atmosphere. Or, finally, light and other radiant effects may be 

 produced, and these are again displacements of some hypo- 

 thetical " substance," called the ether of space. 



Dense T>en se Dense 



l^a. re. TZare. 

 FIG. 47. DIAGRAM OF A SERIES OF SOUND WAVES IN THE AIR. 



The distance apart of the dots represents the condensation and 

 rarefaction of the air. 



Thus the older mechanics and the classical chemistry deal with 

 the displacements of bodies or of molecules or atoms that is, 

 they deal with movements of material substance while the newer 

 physics and chemistry now deal with radiation which occurs in 

 a medium (the ether) invented to enable us to describe the 

 radiation. Everything now becomes vibratory motions or 

 waves. What is a wave ? "If you ask a mathematician," says 

 Sir Oliver Lodge, " what he means by a wave, he will probably 

 reply that the most general wave is such a function of x and y 

 and t as to satisfy the differential equation: 



while the simplest wave is: 



y=a sin (x vt), 



and he might possibly refuse to give you any other answer." 

 He would, no doubt, be sure that you ought to know what a 

 differential equation means, anyhow ! Well, all science that is 

 quantitative expresses itself in such statements: the ether is 

 really a set of differential equations. When a scientific result 

 reaches such a form it tells us that there are certain ratios of 

 displacements. In the above expression the d's are differentials 



