166 CHEMICAL CHANGES 



CHAPTER VIII. 



ACTINISM CHEMICAL RADIATIONS. 



Tlie Sun-ray and its Powers Darkening of Horn Silver 

 Niepce's Discovery Prismatic Spectrum Refrangibility of 

 Light, Heat, and Actinism Daguerre's Discovery Photo- 

 graphy Chemical Effects produced by Solar Radiations 

 Absorption of Actinism Phenomena of the Daguerreotype 

 Chemical Change produced upon all Bodies Power of 

 Matter to restore its Condition Light protects from Che- 

 mical Change Photographs taken in Darkness Chemical 

 Effects of Light on organized Forms Chemical Effects of 

 Solar Heat Influence of Actinism on Electricity Radia- 

 tions in Darkness Moser's Discoveries, &c. 



HEAT and light are derived from the sun, and we have 

 attempted to show, not only that the phenomena of 

 these two principles are different, but that they can 

 scarcely, in the present condition of our knowledge, be 

 regarded as modified manifestations of one superior 

 power. Associated with these two remarkable elements, 

 others may exist in the solar rays. Electrical pheno- 

 mena are certainly developed by both heat and light, 

 and peculiar electric changes are produced by exposure 

 to sunshine. Electricity may be merely excited by the 

 solar rays, or it may flow like light from the sun. 

 Chemical action may be only due to the disturbance of 

 some diffused principle ; or it may be directly owing to 

 some agency which is radiated at once from the sun. 



A sun ray is a magical thing : we connect it in our 

 fancy with the most ethereal of possible creations. Yet 

 in its action on matter it produces colour ; it separates 

 the particles of solid masses farther from each other, 



