335 
Undulatory Theory of Light, as opposed to the Emission 
Theory of Newton, esteeming the former to be true, and the 
latter false science. 
33. But if I am right in this I must necessarily conclude that 
the undulations, pulsations, or vibrations must take place in 
some medium which is not of the gross and material (that is, 
ponderable) nature of that which we usually call matter. 
34. It is not a little remarkable that the profound contempla- 
tions of Sir Isaac Newton should have led him to the following 
inquiries :* — “ Is not heat conveyed through a vacuum by the 
vibrations of a much more subtle medium than air ? Is not this 
medium the same by which light is refracted, and reflected, and 
communicates heat to bodies, and is put into fits of easy trans- 
mission and reflexion? Do not hot bodies communicate their 
heat to cold ones by the vibrations of this medium? And is it 
not exceedingly more rare and subtle than the air, and exceed- 
ingly more elastic and active ? and does it not readily pervade 
all bodies? and is it not by its elastic force expanded through 
all the heavens.” It is remarkable that the undulatory theory 
of light, in displacing his own, should have lent the most beautiful 
and convincing evidence to the truth of these suggestions. How 
little can we rest upon the authority of great names in science, 
when the same individual at different times may so contradict 
his own opinions. 
35. And that in a point of the utmost importance, for it must 
he admitted that such a scientific fact, if true, is of the grandest 
dimensions. This imponderable ether, if it exists, must neces- 
sarily fill all space, and extend as far as the light is visible of 
the most distant stars. Now, “ it has been calculated that 
some of the stars seen with Lord Rosse ; s telescope shine 
from such an enormous distance that light takes upwards of 
50,000 years in travelling to us from them. Now, consider for 
a moment the flight of a light ray from a star at this distance 
on one side of our system to another as far off on the opposite 
. side. For 100,000 years the light speeds onwards, each second 
sweeping over nearly 200,000 miles, past stars and systems. It 
rushes on, but far away ; on every hand are other stars and 
other systems, to which it comes not near. During 5,000 
generations of mortal men, if one can conceive that our race 
could last out that time, the pulsations of the ether are 
transmitted along the tremendous line which separates the two 
stars.”f 
Optics, by Sir Isaac Newton, 
t The Orbs around us, Proctor, p. 45. 
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