Finally: as his view is Newtonian, it is liable to all the objections to which that theory is liable: such as the _diminution_ which would take place at the source from whence the light came; and the _destructive force_ with which it would fall at the surface of the earth. These considerations, with others, have influenced many of the most learned and acute philosophers to look for another theory. Our own countryman, Dr. Franklin, felt them. He says, in a letter dated April 23, 1752, in reference to the theory, of light being _particles of matter driven off from the sun’s surface_; “Must not the smallest portion conceivable have, with such a motion, a force exceeding that of a twenty-four pounder discharged from a cannon? Must not the sun diminish exceedingly by such a waste of matter, and the planets, instead of drawing near to him, as some have feared, recede to greater distances, through the lessoned attraction? Yet these particles with this amazing motion, will not drive before them, or remove the least, and slightest dust they meet with, and the sun appears to continue of his ancient dimensions, and his attendants move in their ancient orbits.” He then supposes the phenomena of light may be more satisfactorily solved by supposing a subtle fluid, universally diffused, which is invisible _when at rest_, but _becomes visible when put in motion_, by affecting the nerves of the eye, as the vibrations of the air affect the ear, and produce the sensation of sound; and that the different degrees of intensity in the vibrations, will account for the different colors. _See Nicholson’s Encyclopedia_, LIGHT. This is the _vibratory_ or Cartesian system of light. As already suggested, it supposes the existence of a subtle, luminiferous ether, diffused throughout the universe, pervading every particle of matter, and is capable of being put in motion, so as to become visible, by the sun, as the grand natural _excitant_, friction, combustion, compression, &c. The _laws_ of the vibrations of this luminiferous fluid, are precisely the same with those ascertained, and determined, in regard to light as commonly understood. This luminiferous fluid is to be considered an elementary substance, and was created when the different substances composing the chaotic mass were created. At its first creation, like caloric, it was in a _latent_ state, as no excitant as yet had put it in motion.