whose soap they used.

It is possible that some of you may like to know why I have chosen
soap-bubbles as my subject; if so, I am glad to tell you. Though there
are many subjects which might seem to a beginner to be more wonderful,
more brilliant, or more exciting, there are few which so directly bear
upon the things which we see every day. You cannot pour water from a jug
or tea from a tea-pot; you cannot even do anything with a liquid of any
kind, without setting in action the forces to which I am about to
direct your attention. You cannot then fail to be frequently reminded of
what you will hear and see in this room, and, what is perhaps most
important of all, many of the things I am going to show you are so
simple that you will be able without any apparatus to repeat for
yourselves the experiments which I have prepared, and this you will find
more interesting and instructive than merely listening to me and
watching what I do.

There is one more thing I should like to explain, and that is why I am
going to show experiments at all. You will at once answer because it
would be so dreadfully dull if I didn't. Perhaps it would. But that is
not the only reason. I would remind you then that when we want to find
out anything that we do not know, there are two ways of proceeding. We
may either ask somebody else who does know, or read what the most
learned men have written about it, which is a very good plan if anybody
happens to be able to answer our question; or else we may adopt the
other plan, and by arranging an experiment, try for ourselves. An
experiment is a question which we ask of Nature, who is always ready to
give a correct answer, provided we ask properly, that is, provided we
arrange a proper experiment. An experiment is not a conjuring trick,
something simply to make you wonder, nor is it simply shown because it
is beautiful, or because it serves to relieve the monotony of a lecture;
if any of the experiments I show are beautiful, or do serve to make
these lectures a little less dull, so much the better; but their chief
object is to enable you to see for yourselves what the true answers are
to questions that I shall ask.

[Illustration: Fig. 1.]

Now I shall begin by performing an experiment which you have all
probably tried dozens of times. I have in my hand a common camel's-hair
brush. If you want to make the hairs cling together and come to a point,
you wet it, and then you say the hairs cling together b