CHAPTER XL 



LIGHT. 



Light caused similarly to heat. Propagated differently. Three divisions. 

 Light without heat. Light with heat. Propagated light, 

 Auroras explained. Phosphorescence. Tyndall refuted on molecu- 

 lar motion. Fire-flies. Lighting gas by the finger. Auroras from 

 trees. Candle a guide to light. Four things required to be looked 

 at. The flame. The heat. The light. And light as an object. 

 All light, reflection. The undulating theory disputed. Light 



instantaneous. Light cannot travel half a mile. Sight travels 



286,000 miles a second. Flame not seen in daylight. Astronomical 

 fallacy of star light. Undulation follows Emission into oblivion. 

 Tyndall's security for the continued acceptance of the Undulatory 

 theory, overthrown. 



IN considering this subject, we find that light, or flame, is 

 produced in a similar manner to heat, but it is transmitted 



9 



differently. If we are right in stating heat to be the result of 

 chemical action, between two certain classes of mineral and 

 vegetable atoms, then light is produced in the same way ; and, 

 in most instances, we cannot get one without the other. Light 

 however does not always indicate, or give heat, and some 

 materials do not afford such a bright light as others. This is 

 owing, we believe, entirely to the proportion, condition, and 

 position of the materials yielding the light. For example, a 

 lamp may not give a very bright light by itself, but put a glass 



