t, because after you have
touched the lever and the card is punched it slides into its own
compartment. You have all the chance you want to look over your
arrangement of depressed keys before the card is punched, but none
after."

Before a week had passed by, Hamilton was so thoroughly at home with the
machine that the work seemed to him to become more or less mechanical,
and his interest in it began to wane. As--under government
regulations--he left work early, he sauntered over several times to the
verification department to become familiar with the work of the machine
used there. There was a fascination to the boy in this machine, for it
seemed almost to possess human intelligence in its results, and he was
curious to know the principle on which it worked. Generally every one
quit at half-past four o'clock, just as he did, but sometimes a man
would work a few minutes longer to finish a batch of cards, and the boy
would go to watch him.

When he was over there one day, after hours, Hamilton saw Mr. Cullern on
the floor.

"Still looking for information?" questioned the older man, with a smile.

"Yes, sir," answered the boy, "I've been watching this machine and I've
spoken to one or two of the operators about the principle of it, but
they none of them seem to know. They knew how to run it, and that was
about all."

"The principle is simple enough," the chief replied, "but it would be a
bit hard to understand the combination unless you had the clew. Then it
is all as clear as day, although the machine itself is a little
complicated. You noticed, of course, that the operator lays a card on
this plate which is full of holes, and you probably noticed that these
holes correspond with the points on the card, and that the way in which
the card is fed into the machine insures that the holes shall coincide
exactly."

"That I saw," Hamilton answered, "and I could see, of course, that
this was one of the most important parts of the machine, and that upon
it a good deal of the exactness of the work depended."

[Illustration: TABULATING MACHINE. Mechanism whereby the punched cards
are verified and every error prevented, and which also tabulates and
numbers all records taken. (_Courtesy of the Bureau of the Census._)]

"It does," the other replied. "Now if you look into those holes in the
plate you can see a little cup of bright metal under each hole. What do
you suppose that is?"

"I'm not sure, of course," the boy respo