260 REPORTS ON THE STATE OF SCIENCE. — 1916. 



' header ' into his machine because the tool on which he was putting his 

 weight shpped. 



This last case is, however, somewhat complicated, and is illustrated 

 by several of the examples given below. The exact stages in the 

 occurrence would usually be somewhat as follows : — 



1. The man applies too much pressure. 



2. The tool slips and thus removes all support from the man. 



3. The man falls into, or part of his body moves into, a dangerous 

 spot. 



4. The machine inflicts an injury. 



Here Stage 4 is due to the usual action of the machine, but the 

 other stages are all unusual. 



This case might be classified separately as * unusual position of the 

 injured man due to unusual action of material due in turn to unusual 

 action of the injured man at the time,' but to avoid a profusion of classes 

 the Stages 1 and 2 may be considered as cancelling out, and therefore 

 forming an absence of, external circumstances beyond the injured man's 

 control at the time. If the tool slipped, not because of excessive human 

 pressure, but because it had become worn or was otherwise defective, 

 then, of course, such external circumstance would be present. 



The analysis has now proceeded far enough to show what is the 

 influence of the human element in each class of accident. The human 

 factor, with its liability to recklessness, to inattention and to insufficient 

 muscular co-ordination, obviously preponderates wherever, amid usual 

 conditions, it was an action or position of the human body that was 

 unusual at the time, or else wherever an unusual movement or position 

 of a material object was caused by a human being at the time. 



But even in one of the classes of causes of accident that remain, 

 namely, where the dangerous movement of the material object was due 

 to natural causes, the fact that an accident ensued in some cases 

 depends on a human element. Suppose that in hoisting a load on a 

 crane the load swings over and hits a man on the head,' he might 

 have avoided it. What chance of escape such a man actually has, 

 depends firstly on whether the hoisting was part of his own work to which 

 he should have been attending, and, secondly, what length of warning 

 the unusual move of the material would give. If the material object 

 fell noiselessly from a height, and to watch it was not part of the 

 injured man's work, then no human element was present in the causa- 

 tion of the accident whatever. A human element would, however, be 

 introduced if the man had been inattentive, or else attentive but slow 

 in escape. 



It is now possible to place in order each class of causes of accidents 

 that has been formed, according to the degree to which the human 

 element enters into them. First would come the accidents due to the 

 action of the material which no human capacity could have foreseen or 

 avoided at the time ; secondly, accidents which a high degree of attention 

 might just have foreseen; thirdly, accidents which a quick reaction 

 {i.e., presence of mind) might have escaped; fourthly, accidents which 



' See example D below. 



