216 FRAGMENTS OF SCIENCE. 



images of processes which, though mighty in the aggregate 

 beyond all conception, are so minute individually as to 

 elude all observation. It is the waves of air excited by 

 this tuning-fork which render its vibrations audible. It is 

 the waves of ether sent forth from those lamps overhead 

 which render them luminous to us ; but so minute are these 

 waves, that it would take from 30,000 to 60,000 of them 

 placed end to end to cover a single inch. Their number, 

 however, compensates for their minuteness. Trillions of 

 them have entered your eyes and hit the retina at the back 

 of the eye in the time consumed in the utterance of the 

 shortest sentence of this discourse. This is the steadfast 

 result of modern research ; but we never could have reached 

 it without previous discipline. We never could have 

 measured the waves of light, nor even imagined them to 

 exist, had we not previously exercised ourselves among the 

 waves of sound. Sound and light are now mutually help- 

 ful, the conceptions of each being expanded, strengthened, 

 and defined, by the conceptions of the other. 



The ether which conveys the pulses of light and heat 

 not only fills the celestial spaces, bathing the sides of suns 

 and planets, but it also encircles the atoms of which these 

 suns and planets are composed. It is the motion of these 

 atoms, and not that of any sensible parts of bodies, that 

 the ether conveys ; it is this motion that constitutes the 

 objective cause of what in our sensations are light and 

 heat. An atom, then, sending its pulses through the infi- 

 nite ether, resembles a tuning-fork sending its pulses 

 through the air. Let us look for a moment at this thrilling 

 ether, and briefly consider its relation to the bodies whose 

 vibrations it conveys. Different bodies, when heated to the 

 same temperature, possess very different powers of agitat- 

 ing the ether: some are good radiators, others are bad 

 radiators ; which means that some are so constituted as to 

 communicate their motion freely to the ether, producing 



