Electricity and Galvanism. 123 



Philosophers have almost universally adopted the opinion of matter 

 being constituted by the aggregation of atoms possessing a spherical 

 figure. No one can cast a glance upon a diagram representing a 

 series of spheres without at once perceiving that such bodies cannot 

 touch each other except at certain parts of their peripheries, and con- 

 sequently the existence of interspaces is obvious ; and few subjects in 

 the range of physical science have attracted more attention than the 

 question of the condition of these insterspaces, whether they were 

 merely empty voids, or full of some form of matter — whether, in a 

 word, they were vacua or plena. They have now long been consi- 

 dered to be filled with a light ethereal form of matter, identical, it is 

 presumed, with that which extend beyond the confines of our at- 

 mosphere into infinite space, constituting that great ocean of scarcely 

 ponderable medium in which the great orbs of our system roll on in 

 their respective spheres. The existence of such a medium is now 

 beyond all doubt or question, from the evidence of its retarding in- 

 fluence upon some of those light cometary satellites, some, probably, 

 scarcely denser than mere whisps of vapour, which occasionally visit 

 the neighbourhood of the earth, and which, from their levity, become 

 excellent tests of the influence of a retarding medium. Sir Isaac 

 Newton attempted to calculate the density of this ether, and found 

 that it must be at least 700,000 times less heavy than the air we 

 breathe. Compared to it, therefore, our atmosphere would be far 

 denser than is the solid mass of a granite rock in comparison with air. 

 We know that gaseous bodies, when thrown into a vibratory motion, 

 give rise to certain curious phenomena very different from those ob- 

 served when in a state of rest. When such vibrations are performed 

 with a certain regularity and rapidity, they give rise to musical 

 sounds or tones. In like manner, when the interstitial ether is made 

 to assume analogous movements, a new set of phenomena are display- 

 ed, differing in their character according to the amplitude and rapi- 

 dity of their undulations. Then, when the particles of ether undu- 

 late with a rapidity not exceeding 458 millions of millions in a second 

 of time, we have the well-known phenomenon of heat or caloric 

 evolved ; when the undulations are increased, so as to range from 

 this number to 727 millions of millions, the various tints of light be- 

 come developed in addition to heat ; whilst, if the vibrations exceed 



