Life as a Physical Phenomenon. 163 



less internal motions and constant changes, while minerals 

 may remain unchanged for an indefinite period of time." 



Of course it is admitted that the structure of a plant 

 differs from the structure of a mineral. It seems to be a 

 fixed law of nature that when the compound atoms of 

 water, ammonia, and carbonic acid, are subjected to certain 

 influences, are agitated by certain ethereal waves, these 

 atoms assume a certain form ; while the simple atoms of 

 oxygen and hydrogen, agitated by the waves of an electric 

 current, assume a different form. The product of the four 

 elements may be a sea-weed ; the product of the two, a snow 

 flake. This transformation by certain ethereal undula- 

 tions into molecular rearrangements, which are unlike, 

 demands for its explanation no new force. 



"We can hardly be required to explain the ceaseless 

 changes, which are observed in living structures by any new 

 force if they can be produced from forces already known to 

 exist. It is a well established rule in science to eliminate 

 unknown quantities from the problem when known quanti- 

 ties can supply their places as elements of the problem. 

 Protoplasm is but the arrangement of certain atoms which 

 are peculiarly subject to molecular change, and this may be 

 said of all nitrogenous compounds. 



The decomposition of substances containing nitrogen 

 often evolve a sudden and surprising evolution of force. 

 Witness the explosion of gunpowder when once its atoms 

 are relieved from their unstable relationship by the vibra- 

 tory action of heat. Mineral substances are only stable 

 within certain limits. 



The snow flake which falls upon your hand, a crystal of 

 almost unparalleled beauty, is instantly resolved into an 

 amorphous condition, and from this it is presently trans- 

 formed into thin vapor. Can permanency of structure be 

 claimed as a barrier to the relations of minerals and plants? 



