106 NATURE AND LIFE. 



Van Tieghem, the discoverer of this curious property, very 

 well remarks, to act afterward in complete darkness, and 

 exhaust itself by slow degrees, through transformation into 

 equivalent chemical energy. It appears to lodge itself in 

 phosphorescent sulphur, to reappear under the form of less 

 intense radiations ; it hoards itself up in paper, starch, and 

 porcelain, to come forth anew, after a greater or less lapse 

 of time, through its action on the salts of silver. The pe- 

 culiarity residing in these green cells of vegetables, then, 

 is not an isolated one : it is a special instance of the gen- 

 eral property, inherent in many bodies, of retaining, within 

 their mass, in some unknown form, a part of the vibrations 

 that fall upon them, and of preserving them through trans- 

 formation, to be afterward emitted, either in the state of 

 luminous radiations, or in the condition of chemical or me- 

 chanical energy. The great principle of the transformation 

 of forces thus holds good in the vegetable kingdom. And 

 we end with the remark that these facts of persistent ac- 

 tivity, called out by an initial excitement, lend support to 

 the idea that living forces hold a close connection with the 

 molecular structure of bodies, and may even be the deter- 

 minate expression of that structure. We cannot conceive 

 manifold energy in a mathematical and irreducible atom ; 

 but in a molecule, made up of a certain number of atoms, 

 we can fancy dynamic figures of a very complex order. 



We have thus far regarded only the action of white light, 

 the effect of the totality of rays sent us by the sun ; but 

 this light is not simple. It is composed of a great number 

 of radiations, of distinct colors and properties. When white 

 light is decomposed by the prism, we obtain seven groups 

 of visible rays, of unequal refractive power, violet, indigo, 

 blue, green, yellow, orange, and red. The spectrum or rib- 

 bon of colors thus obtained widens and spreads out by in- 

 visible radiations. Beyond the red, there exist radiations 

 of dark heat, or calorific rays, and, outside of the violet, ra- 



