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 inte 
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- 
