SECT. 18.] Origin, or Process of Causation of the Series. 73 



the probability curve or law of facility , they do determine 

 its precise value in the cases in question. If, indeed, it be 

 asked why there is no need for any such corrective influence 

 in the case of, say, firing at a mark: the answer is that there 

 is no opening for it except where a cumulative influence is in 

 troduced. The reason why the fortunes of our betting party 

 showed an ever increasing divergency, and why some special 

 correction was needed in order to avert such a tendency in 

 the case of vital phenomena, was that the new starting-point 

 at every step was slightly determined by the results of the 

 previous step. The man who has lost a shilling one time 

 starts, next time, worse off by just a shilling; and, but for 

 the corrections we have been indicating, the man who was 

 born tall would, so to say, throw off his descendants from a 

 vantage ground of superior height. The true parallel in the 

 case of the marksmen would be to suppose that their new 

 points of aim were always shifted a little in the direction of 

 the last divergence. The spreading out of the shot-marks 

 would then continue without limit, just as would the diver 

 gence of fortunes of the supposed gamblers. 



