"Well," the other continued, "when the pin, passing through the hole in the card, drops into the little cup of mercury it closes a current passing through an electro-magnet controlling a counter or a dial corresponding with each possible item of information on the card, and for each contact made to each dial, an added unit is registered. The tabulating process is completed by an automatic recording and printing system, somewhat along the stock ticker plan, connected with each dial. When desired, touching an electric button will cause every dial to print automatically the number recorded on a ribbon of paper." "That is before sorting?" "Or after. Cards may be tabulated along a lot of different lines. And the sorting device depends again upon another machine, operated by the same principle." The chief led the boy to another portion of the floor. "This sorter," he said, "can be set for thirteen different compartments. In determining the country of birth, for example, at any given point on the card, an electrically charged brush finds the hole punched and directs the card in between two of those finely divided wire levels, where a traveling carrier picks it up and runs it along to the point where the wires stop, the top wire extending to the furthest compartment. As the card falls, it is tilted into place against the pile of preceding cards, an automatic receiver holding them together, the operator clearing away the pile from each division as it becomes full. As you can see, that feed knife moves so rapidly and the endless band fingers carry the cards out of the way in such a hurry that they move along in a steady stream. We have only twenty of these machines and they handle all the cards." "It's hard to believe," said Hamilton wonderingly, "that these machines don't think." "We're just building one in here," the supervisor replied, leading the way into a little partitioned-off section of the room, "that has an uncanny ingenuity. This machine feeds itself with cards, verifies and tabulates at an incredible speed. It took some time to perfect all the adjustments, but it is running finely now, and it will simplify the work of the next census amazingly, just as the machines you saw have made the old hand punching machines of former times seem very cumbersome. But this one," he added, "is a gem." [Illustration: PIN-BOX AND MERCURY CUPS. Details of mechanism which almost magically detects mistakes in any census card. (_Courtesy of the Bureau of the Census._)] "It's a little like magic, it seems to me," said Hamilton, "to think of every person in this whole country being registered on a card with a lot of little holes in it, and practically the whole history on it. It certainly is queer."