"For example if 'Na' for naturalized is punched on the same card as 'N' for native-born, and things of that sort, I suppose?" the boy questioned.
"And many others of similar character," the older man agreed.
"But how about insufficiently punched cards?" queried Hamilton. "I can see that it would be easy to arrange the wires so as to catch really bad inconsistencies, but supposing a figure were only left out, there would be no contact made to show the error."
"Except in the age column," was the reply, "there is supposed to be a punch in every field and only one. Any field which does not have a contact from every card registers its disapproval by throwing out that card."
"And what happens to the rejected cards?" asked Hamilton, with interest.
"A checker-up compares them with the original schedules, and if incorrectly punched, punches a new card, if only insufficiently punched, punches the missing place. But the number of cards found wrong does not reach a high percentage."
"You know I've been thinking," Hamilton said thoughtfully, "that while I suppose it is all right getting all those holes punched in a card, and so forth, I should think it would be fearfully hard to handle the card afterwards. All these little holes look so much alike."
"To the eye, perhaps," the chief said, "but you must remember that these cards are never sorted by eyesight. And you must remember that the sorting process is done by machinery all the way along, just as the verifying and the tabulating is handled in a purely mechanical fashion. You remember that each card was punched with a gang-punch?"
"Of course," the boy said, "that was to specify the district."
"We keep all those together from the time they are punched till after we are through with the verifying, so that all the cards of a certain enumeration district, and of every section in that district, are kept together in a separate box."
"My word," Hamilton exclaimed, "what a storage you must have!"
"You ought to go down and see it some time," the other said. "It's big enough, with every State and every county and every district in the country having its own place, and every little village in that district right where it belongs in a box of its own, under that State, county, and district. I'm telling you this just to show you that we don't have to sort the cards for location at all, and that in itself saves us a lot of labor and time."