2O VIBRATIONS TRANSMIT IMPULSES 



between the dark clouds and the earth, expressed 

 this idea in Jupiter's address to the council of 

 gods : 



" Let down our golden, everlasting chain, 

 Whose strong embrace holds heaven to earth and main." 1 



The ancient philosophers taught the existence 

 of an etherial medium occupying the space inter- 

 vening between the grosser particles of bodies ; 

 and for many ages after the doctrine was accepted, 

 and transmitted to later times as " the theory of 

 phlogiston;" a term derived from the Greek 

 PHLOGOS, flame. With modifications, the doc- 

 trine of a universal ether still prevails, and is 

 confirmed by the conclusions of the most acute 

 observers, as well as those of the most profound 

 intellects of our day. 



As to the nature of this ether, all we know is 

 its capability of transmitting the slightest impulse 

 of mechanical force. Beyond this, we must make 

 the same acknowledgment of the limitation of 

 human powers of perception as Faraday makes 

 in reference' to the essential nature of all kinds of 

 matter, when he affirms, " All we know of matter 

 is its power of transmitting action ; " or, as does 

 another eminent writer, in treating of molecules 

 as merely "centres of forces" admitting them to 

 be too minute to be distinctly recognized. 



Passing by, then, all speculations as to the na- 

 ture and constitution of the universal ether, it is 



1 Iliad, book viii. 



