It is quite clear that illustrations of mental prepossession, as also of inertia, may be found in many of the industries and occupations of life. The bicycle has added a very characteristic one. At a certain stage in the acquisition of the art of cycling, there comes a time when every obstacle and irregularity in the road absorbs the attention of the rider with a fascination that is quite irresistible. The rider is so possessed with the idea that he or she is going to run into the post or the curb or a rut or another vehicle, that the dreaded calamity may actually ensue. When the attention can be directed to the clear pathway, and the obstacles driven out from the focus of attention, the difficulty is surmounted. So in jumping or running and in other athletic trials, the entertainment of the notion of a possible failure to reach the mark lessens the intensity of one's effort, and prevents the accomplishment of one's best. He who hesitates is lost, because the hesitation makes possible the suggestion of a failure, the prepossession by a sense of difficulty. II 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.