mbracing that it is called a law of nature.
Those great generalisations, the laws of gravity and the laws of
evolution, or the laws of chemical combination, have a beauty and dignity
which appeal to everyone.

And on the practical rather than on the theoretical, side there is
wonder, and to my mind beauty, in the bigness and in the smallness of the
spaces that man can deal with. The astronomer measures out his work, not
by miles, but by the inconceivable distance that light can travel in a
year. The man who studies bacteria measures by the micron, 25,000 of
which go to the inch. To me there is more fascination in the very small
than in the other extreme. It is wonderful to think that a plant--a big
tree for instance--is made up of countless millions of cells, each of
which was built by a minute protoplasmic body, which Huxley has compared
to a delicate Ariel imprisoned like Shakespeare's sprite in an oak-tree.

There is a dramatic effect in even the simplest of experiments. I, for
one, am never weary of the time-honoured demonstration of a water-plant
giving off oxygen as it assimilates. A twig of Elodea in a large beaker
of water gives off no bubbles in the dull light at the back of the room,
but when close to the window it does so. And with proper precautions the
rate of bubbling becomes an accurate measure of the intensity of
assimilation. To complete the demonstration the experiment should be
repeated with water which has been boiled, and therefore roughly freed
from CO2, when the rate of bubbling is very greatly diminished. Finally,
by blowing vigorously into the water it may be charged once more with
CO2, and the normal rate of bubbling may be established.

There are of course innumerable experiments in pure chemistry and physics
which have this romantic quality in the manner in which they reveal the
secrets of the invisible structure of matter--but of these I have not
much personal experience.

I think, too, that the human interest of science should always be
encouraged. I mean that those classical experiments, by which great men
have advanced human knowledge, should be shown: and performed moreover by
the original methods, _e.g._ the discoveries of Black, Priestley and
Cavendish.

After all, the real fun of science begins when one finds out something
that was not known before. This is what is rather pompously called
original research. It is interesting to see in my father's life how the
sporting