colours for granted? Are they just part of things in general? How do we come to see them? To what is colour blindness due? 'What happens when we see red? Such questions have occupied philosophers and poets for thousands, and scientists for hundreds of years. And yet we are still very much in the dark. The merest tip of the curtain is now being lifted from the stage of the problem. In the meantime, here are some of its essentials. Why Does a Tomato look Red Three factors are responsible for the colour which every day objects present to us. In the first place, there is the illuminating light. Just as a musical note is characterised by a frequency of vibration as shown by a tuning-fork, so light is made up of radiation-each of which has a special frequency due to vibrating atoms. But, in the case of light, the frequency is measured in directly, by determining the wave-length of the light--the dis tance between two crests of the minute waves which go to make up the radiation. Thus, a tomato vvill be visible only if the right amount of suitable frequencies will strike it. In the second place, the chemical constitution of the struck surface plays an important role. In the case of the tomato, it is such as to reflect light consisting largely of longer wave lengths. In connection with the leaf, however, light of medium wave-lengths is the principal portion reflected, and in the forget-me-not the reflected light consists mainly of short wave-length radiation. An Attribute of the Mind This brings us to the third point-the eye. Obviously, a colour is not just "there," it must be seen to be called a colour: colour is an attribute of the mind. Thus, when light of long wave-lengths reaches the eye, a signal goes to the brain which, in a manner as yet unknown, interprets it as "red". Similarly, medium wave-lengths give rise to a signal which produces the sensation of "green," and short wave length light evokes one of "blue". We will need glorified bodies to see and appreciate the glories of heaven. The Christmas lights on Holly wood Boulevard will pale into a dim light in a dark alley in the slums of New York compared to the light and color of heaven. (2) This is not the best part of heaven, however. Heaven is a.place of perfect rest-Rev. 14:13: "And I heard 9
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