SECT. 17.] Origin, or Process of Causation of the Series. 71 



kind of arrangement or distribution, we should not get the 

 same degree of it : there would, on the contrary, be a tendency 

 owards further dispersion. The curve of facility (v. the 

 diagram on p. 29) would belong to the same class, but would 

 lave a different modulus. We shall see this at once if we 

 take for comparison a case in which similar agencies work 

 their way without any counteraction whatever. Suppose, for 

 nstance, that a large number of persons, whose fortunes 

 were equal to begin with, were to commence gambling or 

 betting continually for some small sum. If we examine 

 ;heir circumstances after successive intervals of time, we 

 should expect to find their fortunes distributed according to 

 the same general law, i.e. the now familiar law in ques 

 tion, but we should also expect to find that the poorest 

 ones were slightly poorer, and the richest ones slightly 

 richer, on each successive occasion. We shall see more 

 about this in a future chapter (on Gambling), but it may 

 be taken for granted here that there is nothing in the laws 

 of chance to resist this tendency towards intensifying the 

 extremes. 



Now it is found, on the contrary, in the case of vital 

 phenomena, for instance in that of height, and presumably 

 of most of the other qualities which are in any way character 

 istic of natural kinds, that there is, through a number of 

 successive generations, a remarkable degree of fixitj^. The 

 tall men are not taller, and the short men are not shorter, 

 per cent, of the population in successive generations : always 

 supposing of course that some general change of circum 

 stances, such as climate, diet, &c. has not set in. There 

 must therefore here be some cause at work which tends, so 

 to say, to draw in the extremes and thus to check the other 

 wise continually increasing dispersion. 



17. The facts were first tested by careful experiment. 



