406 FRAGMENTS OF SCIENCE 



ers, but which here finds a more suitable place than that 

 which it formerly occupied. 



Sitting, in the summer of 1855, with my friend Dr. 

 Debus under the shadow of a massive elm on the bank 

 of a river in Normandy, the current of our thoughts and 

 conversation was substantially this: We regarded the tree 

 above us. In opposition to gravity its molecules had 

 ascended, diverged into branches, and budded into in- 

 numerable leaves. What caused them to do so a power 

 external to themselves, or an inherent force? Science re- 

 jects the outside builder; let us, therefore, consider from 

 the other point of view the experience of the present year. 

 A low temperature had kept back for weeks the life of the 

 vegetable world. But at length the sun gained power 

 or, rather, the cloud-screen which our atmosphere had 

 drawn between him and us was removed and life im- 

 mediately kindled under his warmth. But what is life, 

 and how can solar light and heat thus affect it? Near 

 our elm was a silver birch, with its leaves rapidly quiver- 

 ing in the morning air. We had here motion, but not the 

 motion of life. Each leaf moved as a mass under the in- 

 fluence of an outside force, while the motion of life was 

 inherent and molecular. How are we to figure this mo- 

 lecular motion the forces which it implies, and the results 

 which flow from them? Suppose the leaves to be shaken 

 from the tree and enabled to attract and repel each other. 

 To fix the ideas, suppose the point of each leaf to repel 

 all the other points and to attract the roots, and the root 

 of each leaf to repel all other roots, but to attract the 

 points. The leaves would then resemble an assemblage of 

 little magnets abandoned freely to the interaction of their 



