"
"The pins are in that square box at the end of the long arm which comes
down every time a card is put on the plate, aren't they, Mr. Cullern?"
asked Hamilton.
"Yes, and if there is no card there and the pins in the square box are
started down, they are automatically stopped before they reach the
mercury so as not to make a contact on every point. Also if a card were
there without any holes punched, none of the pins would reach the
mercury and no contact would be made."
"But with a punched census card," interrupted the boy, eager to show
that he understood, "the pins go through the holes in the cards and do
not go through where no holes are punched, so that somehow the number of
holes in the card is registered. But still, there's so much difference
in the cards that I don't see how this machine can verify them, can tell
which are right and which wrong!"
"There is variety enough," answered the chief, "for of the hundred
million cards punched, no two are exactly the same, they could not be."
"Couldn't it happen perhaps that two people of the same age should do
the same work, be both married and so forth?" asked the boy
interestedly.
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