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ether. Of this ether we are in no physical sense conscious, 
though there are the most substantial reasons for the as- 
sumption of its existence, reasons sufficiently cogent to make 
its existence a fact. If we were unconscious of the undu- 
latory activity of the air we should have to resort to the 
assumption of such a subject and its activity to explain the 
production of sound, for in every way light produces its 
effects as sound does. The magnet and luminosity prove the 
presence of some vehicle or subject when atmospheric air is 
absent. Hence atmospheric air neither assists in the forma- 
tion or the production of light, therefore the substantial 
reason for assuming another medium that conatus may pro- 
duce light. Light then does not exist apart from the vi- 
brations of luminiferous ether, yet these vibrations do not 
produce light until they are arrested by a reactionary sub- 
ject. The capability of this ether, then, is to create from a 
luminous force acting within it, a force of vibrations so as to 
produce after reaction the effect called light. Now, it is 
obvious that the capabilities of the atmospheric air cannot 
produce light, nor can the capabilities of luminiferous ether 
produce sound. Hence the two media must be totally 
different in their constitution. But though this is so it is 
equally evident that this ether pervades atmospheric air 
everywhere. I have said respecting a tree that if any ot 
the subordinate conatus of it should overpower the govern- 
ment of the pervading one, the tree, in proportion to such 
resistance and its continuance, comes to an end. And that 
the vibrations of the air can be so made as to destroy the 
effects of each other and so annihilate the cause of sound. 
Similarly the vibrations of luminiferous ether can be made 
to neutralize each other and from light to produce darkness. 
And as in the vibrations of atmospheric air the law of the 
squares of distances holds good, so also it obtains as strongly 
if not more perfectly in luminiferous ether, for the pro- 
duction of light, heat, magnetism, or electricity. But We 
