CLASSICAL AND NEW MECHANICS 147 



phenomena. Thus, to the physicist light of different 

 kinds is distinguished only by the three qualities pos- 

 sible in a mechanical wave; its wave-length, the 

 amplitude of its disturbance, and the complexity of its 

 form. These same qualities must also serve to dis- 

 tinguish sounds, water waves, and many other types of 

 this kind of motion. For the biologist and psychol- 

 ogist, light is distinguished by its tint, intensity, and 

 saturation, the three qualities which affect the sense of 

 sight, and sound is determined by pitch, loudness, and 

 timbre, which affect the auditory nerve. And as there 

 is no relation between the sensations of sight and hear- 

 ing, so there can be no connection between light and 

 sound. While the method of the physicist has the 

 great advantage of unity, yet it suffers from its arti- 

 ficiality, as it tends to bring into undue prominence the 

 mechanical energy involved in producing light and 

 sound and ignores the more important property of 

 these phenomena: their effect on our senses. 



It is generally conceded that we have no abstract or 

 absolute knowledge of a quantity of length, time, or 

 mass. In other words, we can express any of these 

 three quantities only as a numerical ratio with respect 

 to a predetermined standard of the same quantity, such 

 as a yardstick for length, a pound for mass, and a 

 given motion of a clock-hand or of the rotation of 

 the earth for time. And, from this fact, it is often 

 argued that we cannot form any idea of the qualities, 



