Why was newtons value for the speed of sound in air low?

Newton's value for the speed of sound in air was low because he based his calculation on an ideal gas model and did not account for the effects of temperature and humidity on sound propagation. Additionally, he assumed sound traveled as a wave in a medium and applied classical mechanics without considering the complexities of compressibility and the thermodynamic properties of air. As a result, his estimate was significantly lower than more accurate measurements made later.