Linus Pauling: I can tell an anecdote, something that happened to me when I was about 13 years old and had just developed an interest in
chemistry. I already had an interest in physics, and geology, mineralogy before then. In Portland, I was walking along one
evening in the rain, holding an umbrella. The street lights were arc lights so that the light came from a rather small source,
a quarter of an inch in diameter perhaps, the arc between the two carbon electrodes. And I was 150 feet away, saw the arc
light through the fabric of the umbrella. I noticed that there was a rainbow, a spectrum of light, violet, indigo, blue, green,
yellow, orange, red, out to one side of this light and also on the opposite side and above and below and four others at 45-degree
angles. And I wondered "what is it that causes that?" It took me a couple of years to learn. I, I wasn't in the habit yet
of trying to find out things by reading, I waited until I had the course in physics and then learned that as the rays of light
come through and go through the different holes in the fabric they're separated a little from one another so that the path
length is a little different. And for some differences in path length, equal to the wavelength of the light, you get a strengthening
of the color. And for other colors, slightly different wavelengths, these waves interfere, they balance one another out. Consequently
you get the different colors showing up at different angles off from the central beam.
Now, x-rays it turned out, have about the same wavelength as the distances between the atoms in the crystal. Consequently
if you shine a beam of x-rays at the crystal you get this sort of spectrum of x-rays caused by the three-dimensional lattice
of the atoms, which is similar to the two-dimensional crossed grating of the fibers in the fabric of the umbrella. And the
theory is quite straight-forward, sometimes difficult to apply if you have a complicated crystal. Well this is really wonderful.
I had been interested in the question of why different chemical compounds, or even elements, have different properties. What
is it about them that causes sugar to be sweet and salt to be salty? Well that's a rather complicated problem and we don't
know the complete answer now because it involves the structures on the tongue, the tastes buds, that we're still somewhat
ignorant about. But I could ask, why is it that steel is strong? Or, I was interested in metallurgy. I, in fact, my first
year had a course in forging, made a horse shoe and a miner's hammer or pick, with which, a geologist's hammer they're called
and made various other chisels and even a knife for myself, a butcher knife. I was interested in the phenomena associated
with metallurgy. Why is it that pure iron is rather soft? Why, a wire of pure iron can be bent very easily. If you put in
a little carbon, just one-percent of carbon, then you can get a very hard steel that approaches diamond in hardness. Or at
least approaches one of the somewhat less-hard, but still hard metals such as, minerals, such as ruby or sapphire.
So, I was very much interested in these questions and I wanted to know what the structures of crystals were. In the first
three months, two months, that I was a graduate student I prepared a dozen crystals. I read the crystallographic literature,
which was quite extensive, and selected out various substances that formed crystals that experience had shown might be amenable
to successful attack by the x-ray diffraction method. And with Professor Dickinson supervising me when it came to the x-ray
part I, in my little laboratory, would synthesize and crystallize one substance after another and then using the methods that
he showed me, start to determine the structure. And I was disappointed twelve times. The first twelve substances that appealed
to me, whose structures I wanted to determine, turned out to be more complicated than the existing techniques could encompass.
Then we succeeded. Professor Dickinson got a mineral, molybdenite, and we made the x-ray pictures and analyzed them. I had
soon started making some other substances whose structures I could determine. Then I was off, I made I don't know how many,
I counted them up once.