90 Lifr mul Lcften* of Franrin (w'afton 



or the stupid side, liatl great interest for Galton iiiul he recurred to the 

 problem many years afterwards, as I shall indicate later in this work. 



Having reached series like this Galton considered how he should represent 

 them theoretically, and he came to the conclusion that the proper method 

 would be to use the normal curve, or curve of errors of the astronomers. 

 Thi.s had alrejidy been used by Quetelet for jifu/siad niea-suremcnts and he 

 cites as illustrations the distributions of measurements of 5738 Scottish soldiers 

 for chest size and of 100,000 French soldiers for stature. These results from 

 Quetelet are from our present standpoint not very convincing; but sui> 



11 

 ily rejvl evidence (Jalton gives (p. 33) 

 on this point is to show the marks obtained by 72 Civil Service Candidates 

 in fact and in theory. Tested by modern methods the theory fits the facts 

 to the extent that if the theory were true one sample in six would give 

 results more divergent from the theory than the observed facts are. It can- 

 not therefore be said that Galton demonstrates that intellectual ability is 

 distributed according to the normal law of deviations. We are not even 

 certain of that to-day. But demonstration was not really needful for Galton's 

 purpose; he could legitimately classify human intelligence by applying a 

 'normal scale' to it, and he would still have his eight classes A, B, ... F, G 

 and A' above and a, b, ...f, y and .r below the average, l)ut he could not claim 

 that these grades were separated by equal "amounts of intelligence," altiioiigh 

 more recent experience — i.e. with (juantitative mental-tests— suggests that it 

 is approximately con-ect. 



Galton's classes: F, 1 in 4300, G, 1 in 79,000 and X, 1 in 1,000,000, cor- 

 respond roughly to his three highest grades of intelligence. Galton then 

 gives the following more popular description of his classification : 



"It will be seen that more than half of e^ich million is contained in the two nu^diocre classes 

 a and A ; the four nie<liocre ela.sses a, b, A, li more than four-fifths an<l the six mediocre classes 

 nion- than nineteentwentieths of the entire population. Thus the rarity of commanding ability, 

 and the vast abundance of mediocrity is no accident, but follows of necessity, from the very 

 nature of these things. 



The meaning of the word 'mediocrity' admits of no doubt. It defines the standard of 

 intellectual power found in most provincial gatherings, because the attractions of a more 

 stirring lif<! in the metropolis and elsewhere are apt to draw away the abler classes of men, 

 and the silly and the imljecile do not take a part in the gatherings. Hence, the residuum that 

 forms the hulk of the general society of small provincial places, is commonly very pure in its 

 n)c<liocrity. The cla.s8 C possesses abilities a trifle higher than those commonly pas-sessed by 

 the foreman of an ordinary jury. D includes the muss of men who obtain the ordinary prizes 

 of life. E is the stage higher. Then we reach F the lowest of those yet superior classes of 

 intellect, with which this volume is chiefly concerned. 



On descending the scali-, we find hy the time wo have reached ./J that we are already among 

 the idiots and imlx:ciles. We have seen. ..that there are 400 idiots and imlwciles, to every 

 million of persons living in this country; but that 30 per cent, of their nunilxjr appear to bo 

 light cases, to whom the name of idiot is inappropriate. There will remain 280 true idiots and 

 imijeciles to every million of our population. This ratio coincides very closely with the require- 

 ments of classy. 



Hence we arrive at the undeniable, but unexj>ected conclusion, that eminently gifted men 

 are raised aa much above mediocrity as idiots are depressed below it; a fact that is calculated 



