Conclusion. 
515 
solid, are everywhere forces producing movement and change. 
Moreover there is abundant reasons for believing that these 
forces are still as potent and their resultant transformations 
as rapid as in the past. The earth is not finished, but is now 
being, and will forevermore be re-made. 
I am keenly aware that I have failed to give any adequate 
idea of the constancy, universality, and complexity of earth 
movements. Whatever the degree of complication which any of 
us may grasp, we may be absolutely certain that the facts are 
indefinitely more complicated. It is ever so in nature. The ex¬ 
planation first offered of a complex set of phenomena is always 
exceedingly imperfect. In succession, year after year, as new 
facts and principles are discovered, new statements, nearer the 
truth, are made. If the first work was good the explanation 
offered was not false,— it was incomplete. The later, larger 
explanation includes and adds something to the previous imper¬ 
fect one. Each succeeding generation brings the explanation 
nearer completion, nearer perfection. This principle is well 
illustrated by the multiplicity of causes now assigned for the 
contraction of the earth, this being at first wholly attributed to 
secular cooling. 
It is often remarked that it is scarcely worth while to learn 
the scientific theories of today — they will be changed tomor¬ 
row. By certain people, because of this, we are frequently 
warned not to place confidence in the conclusions of science. 
However, the change in science is its chief merit.- Science is 
ever moving nearer the truth. If we would know the secrets 
of the world, the only way is to learn science as it is today, 
and move forward as it moves. The subject in which ideas are 
fixed, in which theories do not change, is dead. 
We may be certain that all who hold a light opinion of science 
because its theories change lack a grasp of the methods of 
science. They may know some of its facts, — of little or no 
value,without at least a partial understanding of the underly¬ 
ing principles which control them, — but they are as ignorant 
of the real teachings and merits of science as is the savage 
The latter may see the electric car move, driven by an invisible 
power. He may be wonder-struck by many other phenomena 
