If we consider the velocity of the vibrations of light, or, in the second case, of the air, which in all probability far outstrips any capacity on our part for forming an immediate judgement in perception of the time interval between them, we should be led to believe that it is only the effect of those vibrating movements upon the elastic parts of our body, that can be evident to the senses, but that the time interval between them is not noticed nor involved in our judgement, and that, consequently, all that enters into combination with colours and tones is the agreeableness, and not the beauty, of their composition.