100 THE BEGINNINGS OF LIFE. 



impacts of the waves are so timed as to correspond 

 with the atoms. The effects of the waves are, in such 

 case, cumulative; and each atom gradually acquires 

 a momentum made up of countless infinitesimal mo- 

 menta.' Mr. Spencer then points out that the elements 

 of a chemically-compounded atom (or c molecule/ as it 

 is usually termed by chemists), being still free to move 

 within certain limits, we. must suppose them to remain 

 severally capable of vibrating in unison with the same 

 kinds of ethereal waves, as were capable of moving 

 them when they were in their uncombined condition. 

 The component atoms, therefore, retain their original 

 rates of oscillation, modified only as they may be by 

 their mutual influence upon one another; whilst the 

 compound atom or molecule will have a capacity of 

 oscillating determined by the attributes of its con- 

 stituent atoms. Taking the case of binary molecules 

 as an example, it becomes evident that if the members 

 of such molecules differ from one. another considerably, 

 they are almost sure to be thrown into different rates 

 of vibration, and c it is manifest that there must arise 

 a tendency towards the dislocation of the two a 

 tendency which may or may not take effect, according 

 to the weakness or strength of their union, and according 

 to the presence or absence of collateral affinities? This 

 inference is perfectly in harmony with certain known 

 facts. The metallic compounds which are most de- 

 composable under the influence of the chemical rays of 

 light are silver, gold, mercury, and lead, all of which 



