188 PHOSPHORESCENCE. 



electric current, we see a certain amount of electric 

 vibration transformed into heat and light, for the 

 wire first becomes hot and then luminous. If we 

 place upon the snow two pieces of cloth one 

 white, the other black the white one reflects back 

 the light of the sun, the dark one absorbs the 

 light, and a certain amount of it is transformed 

 immediately into heat, which, in its turn, is trans- 

 formed into another kind of motion manifested by 

 the melting of the snow under the black clofch. 



In the same way light is transformed into 

 chemical action (as in photographic processes), and 

 chemical action into light (combustion of phos- 

 phorus). So, again, the electricity of the galvanic 

 battery is transformed into its equivalent of light, 

 chemical action, heat, etc., and chemical action 

 gives birth to electricity, light, and heat. 



The motion or vibration of a special organic 

 substance, which motion constitutes nervous force, 

 can be transformed into electricity, and electricity 

 into nervous force. Matteucci, who has made nu- 

 merous experiments upon this subject, distinctly 

 insists upon the necessity of distinguishing be- 

 tween electric force and nervous force. One of 

 these can give birth to the other, and reciprocally ; 

 but they are not identical. When a nerve is 

 excited by an electric current, it immediately oc- 

 casions muscular contractions ; but at this moment 

 not a trace of electricity can be detected in any 



