ste which it is the function to relieve. But
the wonder of it all is how slight a part our wills play in the process,
and how our lives are kept going by a mechanical force from without,
seconded or supplemented by chemical and vital forces from within.

The one chemical process with which we are familiar all our lives, but
which we never think of as such, is fire. Here on our own hearthstones
goes on this wonderful spectacular and beneficent transformation of
matter and energy, and yet we are grown so familiar with it that it
moves us not. We can describe combustion in terms of chemistry, just as
we can describe the life-processes in similar terms, yet the mystery is
no more cleared up in the one case than in the other. Indeed, it seems
to me that next to the mystery of life is the mystery of fire. The
oxidizing processes are identical, only one is a building up or
integrating process, and the other is a pulling down or disintegrating
process. More than that, we can evoke fire any time, by both mechanical
and chemical means, from the combustible matter about us; but we cannot
evoke life. The equivalents of life do not slumber in our tools as do
the equivalents of fire. Hence life is the deeper mystery. The ancients
thought of a spirit of fire as they did of a spirit of health and of
disease, and of good and bad spirits all about them, and as we think of
a spirit of life, or of a creative life principle. Are we as wide of
the mark as they were? So think many earnest students of living things.
When we do not have to pass the torch of life along, but can kindle it
in our laboratories, then this charge will assume a different aspect.

III

Nature works with such simple means! A little more or a little less of
this or that, and behold the difference! A little more or a little less
heat, and the face of the world is changed.

"And the little more, and how much it is,
And the little less, and what worlds away!"

At one temperature water is solid, at another it is fluid, at another it
is a visible vapor, at a still higher it is an invisible vapor that
burns like a flame. All possible shades of color lurk in a colorless ray
of light. A little more or a little less heat makes all the difference
between a nebula and a sun, and between a sun and a planet. At one
degree of heat the elements are dissociated; at a lower degree they are
united. At one point in the scale of temperatures life appears; at
another it disapp