304 



REPORTS ON THE STATE OF SCIENCE.— 1915. 



side with practice, though their influence will be felt at different 

 periods, and, as in the case of fatigue, output and accident distribution 

 may each be somewhat differently affected. The external factors condi- 

 tioning Practice, Spurt, Incitement, and Excitement are the same as 

 those conditioning fatigue, i.e., Previous Duration of Work, Factory 

 Conditions, the Nature of the Work itself and the state of the Worker; 

 though any great effect of Factory Conditions on ' daily ' Practice and 

 Incitement is perhaps doubtful. 



The following chart may make clearer the Causal Relations: — 



Previous duration of work"! 

 of certain workers in cer- 

 tain processes among cer- 

 tain surroundings J 



Previous duration of work) 

 of certain workers in cer- 

 tain processes among cer- 

 tain surroundings 



Condition : Fatigue 



Which I Output decrease, 

 results in { Accident increase. 



Condition ; 



Practice "| /Output 



Spurt I Which I increase. 



Incitement j results in j Accident 

 .Excitement J [ decrease. 



B. The ' outside ' or non-psycho-physical condition which is of 

 most importance as a factor in the time-distribution of both accidents 

 and output without interposing fatigue is Lighting. 



As regards this ' immediate ' effect of lighting on output the In- 

 dustrial Commission of Wisconsin found that a steel plant by just 

 changing its system of lighting could increase its output at night by 

 over 10 per cent. 



As regards immediate effect of lighting on accidents : The National 

 Electric Light Association have published a diagram correlating the 

 monthly proportion of darkness, cloudiness, and sunlight in the city 

 of New York with the monthly fatal accidents in 80,000 industrial 

 plants for three years. In each ' correlation ' the maximum is 

 round January, and the minimum round July. Similarly the accidents 

 per man are higher at night than by day (see Section I.b in the case of 

 iron and steel works). 



To a certain extent artificial and other weak lighting may increase 

 accidents by fatiguing the eyes and attention, and hence lighting is 

 included under the Conditions of Factory Hygiene likely to influence 

 fatigue (Section I.) ; but to a larger extent the relation of accidents and 

 lighting is ' immediate, ' the distribution of accidents over the day being 

 influenced by the growing objective invisibility of danger-points. 



II. Factors besides fatigue that may influence the time distribution 

 of output only are connected with the continuity of the work. If the 

 work is not continuous : if the worker has to prepare his materials at 

 the start of the day and clean up at the end, or if. in course of the 

 day he must wait either because his materials have not reached him, or 

 on account of his machine breaking down, or if at certain times during 

 the day the work must go faster than at other times owing to short 

 time orders, &c., then in so far it is the events of the factory or outside 

 economic circumstances and not fatigue that is affecting the output 



distribution. j- . -i i.- 



III. Factors besides fatigue that may mfluence the distribution 

 over time of day of accident occurrences only are : 



(i) The Magnitude of the Output.— The greater the output the 



