However, Isaac Newton argues that sound consists of waves. He compares the medium of air with a fluid, because the waves in a fluid behave like sound.

Isaac Newton, Philosophiae Naturalis Principia Mathematica, Part 1

Isaac Newton, Philosophiae Naturalis Principia Mathematica, Part 2

Isaac Newton, Philosophiae Naturalis Principia Mathematica, Part 3.1

Isaac Newton, Philosophiae Naturalis Principia Mathematica, Part 3.2