42 Arrargement and Formation of the Series. [CHAP. n. 



in the groups of things in question. This is a not unnatural 

 consequence from some of the data and conclusions of the 

 last few paragraphs. Refer back to two of the three classes 

 of things already mentioned in 4. If it really were the case 

 that in arranging in order a series of incorrect observations 

 or attempts of our own, and a collection of natural objects 

 belonging to some one and the same species or class, we found 

 that the law of their divergence was in each case identical in 

 the long run, we should be naturally disposed to apply the 

 same expression Law of Error to both instances alike, 

 though in strictness it could only be appropriate to the 

 former. When we perform an operation ourselves with a 

 clear consciousness of what we are aiming at, we may quite 

 correctly speak of every deviation from this as being an 

 error; but when Nature presents us with a group of objects 

 of any kind, it is using a rather bold metaphor to speak in 

 this case also of a law of error, as if she had been aiming at 

 something all the time, and had like the rest of us missed 

 her mark more or less in almost every instance 1 . 



Suppose we make a long succession of attempts to measure 

 accurately the precise height of a man, we should from one 

 cause or another seldom or never succeed in doing so with 

 absolute accuracy. But we have no right to assume that these, 

 imperfect measurements of ours would be found so to deviate 

 according to one particular law of error as to present the 

 precise counterpart of a series of actual heights of different 

 men, supposing that these latter were assigned with absolute 

 precision. What might be the actual law of error in a series 

 of direct measurements of any given magnitude could hardly 

 be asserted beforehand, and probably the attempt to deter- 



1 This however seems to be the rate works hy Quetelet, viz. his 

 purport, either by direct assertion Physique Sociale, and his Anthropo- 

 or by implication, of two elabo- metric. 



