636 FRAGMENTS OF SCIENCE. 
external to themselves, or an inherent force? Science 
rejects the outside builder; let us, therefore, consider from 
the other point of view the experience of the present year.. 
A low temperature had kept buck 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 immediately 
kindled under his warmth. But what is life, and how can. 
solar light and heat thus affect it? Near our elrn was a 
silver birch, with its leaves rapidly quivering in the 
morning air. We had here motion, but not the motion of 
life. Each leaf moved as a mass under the influence of an 
outside force, while the motion of life was inherent and 
molecular. How are we to figure this molecular 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 own 
forces. In obedience to these they would arrange them- 
selves, and finally assume positions of rest, forming a 
coherent mass. Let us suppose the breeze, which now 
causes them to quiver, to disturb the assumed equilibrium. 
As often as disturbed there would be a constant effort on 
the part of the leaves to re-establish it; and in making 
this effort the mass of leaves would pass through different 
shapes and forms. If other leaves, moreover, were at 
hand endowed with similar forces, the attraction would 
extend to them a growth of the mass of leaves being the 
consequence. , 
We have strong reason for assuming that the ultimate 
particles of matter the atoms and molecules of which it is 
made up are endowed with forces coarsely typified by 
those here ascribed to the leaves. The phenomena of 
crystallization lead, of necessity, to this conception of 
molecular polarity. Under the operation of such forces 
the molecules of a seed, like our fallen leaves in the first 
instance, take up positions from which they would never 
move if undisturbed by an external impulse. But solar 
light and heat, which come to us as waves through space, 
