THE BEGINNINGS OF LIFE. 99 



that are otherwise combined. The atoms thus united, 

 and thus mixed among others with which they are" 

 capable of uniting, are exposed to the undulations of 

 a medium that is relatively so rare as to seem im- 

 ponderable. These undulations are of numerous kinds : 

 they differ greatly in their lengths, or in the frequency 

 with which they recur at any given point. And under 

 the influence of undulations of a certain frequency, 

 some of these atoms are transferred from atoms for 

 which they have a stronger affinity, to atoms for which 

 they have a weaker affinity. That is to say, particular 

 orders of waves of a relatively imponderable matter, 

 remove particular atoms of ponderable matter from 

 their attachments, and carry them within reach of other 



attachments Now the discoveries of Bunsen and 



Kirchoff respecting the absorption of particular lumi- 

 niferous undulations by the vapours of particular sub- 

 stances, joined with Professor Tyndall's discoveries 

 respecting the absorption of heat by gases, show very 

 clearly that the atoms of each substance have a rate of 

 vibration in harmony with ethereal waves of a certain 

 length, or rapidity of recurrence. Every special kind 

 of atom can be made to oscillate by a special order of 

 ethereal waves, which are absorbed in producing its 

 oscillations ; and can by its oscillations generate this 

 same order of ethereal waves. Whence it appears that 

 immense as is the difference in density between ether 

 and ponderable matter, the waves of the one can set 

 the atoms of the other in motion, when the successive 



H 2 



