The Franklin Institute Logo
Case Files logo

Herman Hollerith: Electric Tabulating Device, 1890

Mercury Cups

The mechanical/electrical detection device for each column consisted of a hard rubber bedplate containing an arrangement of small cups of mercury which coincided with each possible hole location on the card. After placing the card over this array the operator pulled down a "pin-box" of spring-loaded pins with exactly the same arrangement as the mercury cups. Pins which passed through a hole dipped into the mercury cups and completed the circuit to an electromagnet which advanced the corresponding counter dial by one unit. The operator hand copied the tabulation totals and reset the dials to zero at the end of each run.

card

Census Table of Place of Birth Codes, 1889 (398k)

card

Census Table of Occupations Codes, 1889 (642k)

card

Census Form F - MALE FOREIGN Occupation, 1889 (1007k) | Page 2 (994k)