NATURE OF HEAT AND LIGHT. 15 



answer, naturally force themselves upon the attention of every 

 thinking mind which observes their astonishing effects. Formerly 

 the material theory, which regarded heat and light as fluids of 

 inappreciable tenuity stored up in the inter-atomic spaces of 

 bodies, and evolved under certain circumstances so as to become 

 sensible to the touch or vision, had the greater number of ad- 

 herents ; but recent discoveries leave no doubt of the truth 

 of the dynamical theory, according to which they are merely 

 accidents or conditions of matter namely, motions of its ulti- 

 mate particles. These motions or vibrations communicate their 

 undulations to the highly elastic ethereal fluid which fills all 

 space, and in which the hosts of the celestial bodies are plunged, 

 like islands in an infinite ocean. Eays of heat and light without 

 number, proceeding as messengers of life from countless suns, 

 cross each other in that vast interstellar sea itself the seat of 

 perpetual cold, of perpetual silence, of perpetual darkness, of 

 perpetual death. But are these silent realms mere useless voids, 

 mere dead and dreary wastes ? No ! for through them warmth 

 and light radiate from world to world ; they form a necessary link 

 in the chain of influences and motions from which life proceeds, 

 and without their night there would be no day, and no beings 

 to enjoy the day and its infinite variety and beauty. 



