A CENTURY OF CHEMISTRY. 121 



lamp. We know that heat, light, and electricity are 

 transformable powers. 



But any common green plant is the seat of trans- 

 formations of energy not less marvellous. The ener- 

 gies of the sunlight — the undulations of the ethereal 

 waves, according to the student of physics — are so 

 used by the plant that complex organic substances, of 

 which starch is the first to become visible, are built 

 up. The kinetic energy of the sunlight is changed in 

 the potential energy of complex chemical substances, 

 such as wood. We use such potential energy to sup- 

 ply power to our life, to stoke our engines, to warm 

 our hearths. 



We know of no life which is not life-born, but we 

 know that all the world over, from the red-snow plant 

 of Arctic icebergs to the luxuriant vegetation of the 

 Tropics, from the seaweed on the shore to the Cali- 

 fornian Wellingtonias, the simple so-called dead ele- 

 ments of water, earth, and air are being quickened 

 into life, that is to say, are becoming part of the 

 capital of living plants. On these plants animals 

 feed, and the wealth of the plants is recoined to feed 

 muscle and nerve, and what was once the dust of the 

 wayside may become part and parcel of the brain of 

 a Caesar. 



Elements in an Organism. — Let us approach the 

 subject in another way. ^o one knows the chemical 

 nature of living matter, for we cannot isolate what is 

 genuinely alive from associated not-living substance. 

 Moreover, the moment the expert begins his analysis 

 the living matter is dead, and the secret eludes him. 

 But every one now knows the elements out of which 

 the living body is built up, though no one can tell 

 how these elements are arranged in really living 

 stuff nor how they act as they do when thus ar- 



