t
cases clergymen of the Church of England?" This person had no conception
of what the word 'knowledge' means as understood in science.

Another characteristic of science is that it makes us able to predict. I
have already referred to the fact that Queen Anne is dead, and we know,
or are told, that she died, as I said before, in 1714; we also know that
George I. died in 1727, and George II. in 1760, but that would not enable
us to predict that George III. would die in 1820. They are isolated
facts not connected by the causal bond that knits together a series of
scientific truths. And this is after all a fortunate thing for the peace
of mind of reigning sovereigns.

It is said that you should never prophesy unless you know. But science
is made up of prophecies. Some are famous, like the prediction of Adams
and Leverrier that a new planet would be found in a stated position.
Some are on a humbler scale, such as my father's prediction that a big
moth would be found to carry the pollen of Hedychium by brushing it off
with the tips of its hovering wings, a method of fertilisation unheard of
at the time, which however proved to be the fact.

You may say that it does not matter whether the moth does this particular
thing or not. This is no doubt true from a strictly commercial point of
view. But in science all facts have some value. We should cultivate a
point of view about facts the very reverse of that of the unknown person
who said that all books are rather dull.

I once heard a celebrated physicist describe how he explained to an
American business man an elaborate spectroscope for examining the sun.
The American asked what good it was. The physicist explained that with
it you can discover whether or no sodium exists in the sun. The American
was silent for some time, and then said, "But who the 'nation cares
whether there is sodium in the sun or not?" He had not the scientific
spirit which does care about sodium in the sun.

Scientific discovery is, as I said, made up of a series of prophecies.
You observe fact No. 1, and you say if this be so No. 2 ought to be true,
and on examination you find this is true, and No. 2 suggests No. 3. Or
else you find 2 not to be true; this makes you suspect your original
fact, and on carefully going over your observation you find No. 1 was a
mistaken observation. The successful man of science is one to whom
familiar objects suggest those prophecies generally known as theor