Some of the illustrations of prepossession are somewhat trivial; others more important, but perhaps not so definite as might be desired. It is seldom that an instance of this propensity can be pointed out in which an accurate and quantitative comparison may be made between the possessed and the unpossessed mind. One such illustration, which seems to me comprehensive and significant, is worthy of more detailed record.[11] It is derived from the experience of the United States Census office in 1890, in tabulating the returns of the enumeration by means of machines specially devised for this purpose. I give an account of the manipulation of these machines in the words of one who had an intimate acquaintance with their use, and add italics to emphasize the points of special psychological significance.
"The adoption of Mr. Hollerith's tabulating machine for counting the population of the country according, at one and the same time, to sex, color, age, marital condition, nationality, occupation or profession, language and school attendance presented an entirely novel problem to the office. The machines having never been used for any purpose, there was no previous experience by which to act or on which to predicate results. The necessity was upon the office of employing for a very limited time (ninety days) at least five hundred people for this work alone, in addition to the one thousand who could be taken from other branches of the work and placed on this one. Every one, including Mr. Hollerith himself, felt that the rapid and accurate use of the punching machines called for a degree of cultivated intelligence not possessed by every clerk. So much for the mental attitude.
"The clerks (an instructor for every twenty) were taught to edit the family schedules from which the count was to be made, thus learning thoroughly how to read and classify the returns. In order to accommodate the returns to the capacity of a punching machine, a great variety of symbols were adopted for occupations and professions: thus Ad was used for farmer: Ac for farm hands: Kd for merchants: Gd for agents, etc., through twenty-four two-columned octavo pages of ordinary type. Some one symbol must be used for each occupation recorded, and the use of the symbols must be learned, and, for rapid work, they must be committed to memory.[12] _After five weeks of editing_, one by one, the most reliable and intelligent workers were set to use the punching machines. The task is much like that of using a typewriter, substituting for keys a movable punch which passes through lettered holes, and in place of the forty keys of an ordinary typewriter, about two hundred and fifty holes are to be learned.