EFFICIENCY AND FATIGUE 259 



the relatively greater the call upon the physical ener- 

 gies of the body. For instance, it is found 1 that in 

 a man walking at various speeds more than twice as 

 much energy is required per mile of ground covered 

 when walking 5 miles an hour as when walking 2 miles 

 per hour. Hence, if a workman wants to produce a 

 maximum output he must shorten his hours of work 

 as much as possible, so as to reduce the waste of energy 

 arising from much standing about, but he must not 

 shorten them so much as to necessitate a very great 

 speed of production with its much more than propor- 

 tionate call upon his energies. He must endeavour 

 to hit off a happy mean, involving some reduction of 

 hours and sortie speeding up of production, but what 

 the best hours of work and the best speed actually 

 consist in can be determined only by prolonged obser- 

 vation and experiment. These hours necessarily vary 

 considerably with the character of the work performed. 

 We have seen that in men and women engaged in 

 active work such as sizing or turning fuse bodies the 

 best hours of actual work are probably rather less than 

 fifty per week, but in lighter work they rise above 

 this limit. For instance, in the operation of boring 

 aluminium top caps the youths in charge of the semi- 

 automatic machines perform less than two seconds of 

 active work about four times a minute, and for the rest 

 of the time they stand doing nothing. The output 

 data shown in Table III, which were obtained with 

 a group of 15 of these youths, show that when their 

 hours of actual work were reduced from 72.5 a week 

 down to 54.7 hours, their relative hourly output in- 

 creased only from 100 to 117, and so their total out- 

 put was 12 per cent less than before. After some 

 months, however, they were able to speed up their 



1 Cf. Douglas, Haldane, Henderson, and Schneider. Phil. Trans. Royal Soc. 

 B., 203, p. 185, 1913. 



