Men may be changed from gang to gang, or a whole gang may be changed from one job to another, and the time─keeper knows nothing of it unless he happens to be on the spot at just the right time. Such a change would not show in his time record; and while the men would get credit for their full time, the distribution of costs would be much in error. The difficulty in recording such changes can be seen from the following extract from a report of a Consulting Engineer after inspecting work upon a road─making contract: "In one case, at 10:30, there were eight men carrying stone to the crusher, and three men on the crusher platform. Two others were in the cut, loosening earth and loading; and half an hour later, two of the four men who had been blasting were also loosening and loading." [Illustration: Fig. 1. Time─Keeper's Slip. Duplicate record is made automatically on a similar slip by carbon paper.] This, of course, indicates an unusually loose organization, but is an example of what a time─keeper with a notebook has to contend against. In case of emergency──say in steam shovel work──a train of dump cars goes over the side of a dump, and a track gang is called upon to help the regular dump gang so that the difficulty may be overcome as soon as possible. The time─keeper might fail to make record of an hour or an hour and a─half which the track gang put on this work, because he did not see them at work at that particular time. This, of course, affects the distribution of cost. One advantage from the notebook is that much of the distribution is made in the field, with a corresponding reduction of office work. =Punch─Cards.= The keeping of time by means of punch─cards has been tried with considerable success on many jobs, but only recently has it been reduced to a practical basis for use on large construction work. The Construction Service Company of New York City has developed a system of time and cost keeping, using the duplicate punch─card almost entirely. Several of these cards are reproduced in connection with this text. As a general thing, the punching of the cards is done by foremen of the gang, or by someone who has the performance of the gang under direct observation. The cards show not only the time worked by each man upon any one day, but just as exactly the time worked upon any job by all the men. A duplicate of the record is made automatically, to be kept in the time─keeper's office, the other going to headquarters for permanent record.