2 to 7, inclusive, showing these fluctuations in power consumption for driving various machinery in the industrial community served, may be compared to advantage with charts obtained from observation on the number of accidents arising through carelessness caused by fatigue, Figure 8, and hourly outputs, Figure 9.1 The valuable part of these comparisons of much dissimilar cases, such as purely manual work of dock laborers, highly mechanistic work in machine shops, and monotonous work of the spinning mill, and a diversity of groups of

FIG. 9. HOURLY OUTPUT AND POWER CONSUMPTION-COMPOSITE WORK-Day

industries such as colliery, foundry, tailor establishments, quarry, china-ware works, repair shop, etc., both in the United States and in Europe, seem to establish beyond much doubt the similarity in waves of fatigue and rest.

2

Generalizations from a typical case or from individual, single-day test, however interesting, are lacking the indications as to how the fatigue accumulates from day to day during the week. Monday's chart' shows undoubtedly a feeling of fatigue after Sunday's rest; while power demand is fairly steady and

1Reproduced from Ch. S. Myers, M. D., Sc. Di., F. R. S.

In Belgium, Russia, and other countries where Ministries of Public Education studied the fatigue of school children, the week is broken on Thursday and the afternoon is given as a holiday to promote the good work.

This phenomenon is known as "incitement" and it may be observed even after very short interruptions. The fall of attentiveness due to this cause is as pronounced as of physical vigor. Firemen just after taking the shift usually drop the efficiency for about 40 minutes. They explain it by the necessity of "putting fires in shape" while in reality it is due to a necessity of putting themselves in shape to observe and operate properly.

peaks are uniformly high in both morning and in the afternoon spells, they do not reach the same heights as on Tuesday when the feeling of realization of fatigue is somewhat worn off; the periods of high output during spells are noteworthy by their durations. On Wednesday morning the fatigue is not felt yet, but in the afternoon it begins to manifest itself by a steadily declining use of power. Thursday is a day when the industrial community becomes really tired; after short effort in the early morning the work drags 14 to 15 per cent. less actively than on Tuesday. On Friday a supreme effort is made at the start of the day by tired men to work hard, but collapse follows at once and the output rapidly falls in an avalanche fashion to the lowest point on the record; Saturday morning finds men without any ambition left, no peaks to indicate any vestige of the morning spell, although fairly high, men probably being spurred by anticipation of the holiday, while some likely are rushing to finish their week's tasks.

The accumulative fatigue, so plainly evident from these graphs, is of the utmost importance: it seems to indicate that

FIG. 10. EFFECT OF WEEKLY ACCUMULATED FATIGUE ON QUALITY OF FIREMEN'S WORK

the seven-day week [traditional since biblical times and suitable for occupations of that degree of civilization] is too long for our days of strenuous effort. But it also suggests a desirability of securing similar data for 52 weeks of the year showing the accumulation of fatigue throughout the year. Unfortunately, this kind of data is exceedingly difficult to secure because of seasonal fluctuation of the amount of work, number of employees, climatic changes, and numerous other interfering factors.1

However, these wavy lines of fatigue and spells have a great deal more than academic value. By careful study of them the possibility of combatting the ill-effect of fatigue on health, safety, and productivity may be devised. In certain manual operations performed in power plants such as wheeling of coal, the intermittent work and rest periods were arranged after exhaustive tests with the result that men who were fatigued and ready to "fire the job" not wanting to "kill themselves" by wheeling in 45,000 pounds of coal in 12 hours, were made contented, and thought the job is a "cinch" when, by following our instruction, they wheeled in 60,000 to 65,000 pounds in 8 hours.

The reduction and general gradual elimination of fatigue through adequate rest and proper recreation, better adapted tools, and surroundings of work, substitution of interest in work for monotony, etc., is the task of utmost importance from the viewpoint of national economy as it at once not only conserves the health of the nation and increases the productivity and well-being of the community but it materially conserves our fuel resources for posterity.

The task of engineers viewed in this light is to provide opportunities for leisure rather than to invent new yokes and tread mills.

It was reported that the work of women in munition factories falls immediately after Christmas by 6 per cent. due to "incitement," while soon afterward the output reaches 12 per cent. above the pre-holiday maximum which, due to expectation of vacation, is from 6 to 10 per cent. above normal.