“And now, because the soul acts at a distance by some power that belongs to it, are we authorized to conclude that it exists as something real, and that it is not the result of functions of the brain?

“Does light really exist?

“Does heat exist?

“Does sound exist?

“No.

“They are only manifestations produced by movement.

“What we call light is a sensation produced upon our optic nerve by the vibrations of ether, comprising between 400 and 756 trillions per second, undulations that are themselves very obscure.

“What we call heat is a sensation produced by vibrations between 350 and and{sic} 600 trillions.

“The sun lights up space, as much at midnight as at midday. Its temperature is nearly 270 degrees below zero.

“What we call sound is a sensation produced upon our auditory nerve by silent vibrations of the air, themselves comprising between 32,000 and 36,000 a second.

From “The Unknown.” Published by Harper & Brothers Copyright, 1900, by Camille Flammarion. (French Astronomer)