THE LATEST ARITHMETICAL PRODIGY. 65 



number that he can repeat without mistake. Such trials are 

 common in psychological laboratories. According to my personal 

 observations, persons can repeat on an average from seven to ten 

 figures without making a mistake, when they are pronounced 

 with a rapidity of two per second. The division of figures into 

 groups, the special vocal intonation, or some kind of rhythm, are 

 artifices which may sometimes increase the number, and make the 

 effort to repeat less painful. These results agree with those of an 

 American psychologist, Mr. Jastrow, who mentions 8.5 as the 

 average number found among pupils in his country. 



M. Inaudi has practiced this kind of repetition for a long time. 

 We repeat the number, dividing it into periods of three figures 

 each, and giving the value of each period. For example, to make 

 him repeat the number 395,820,152,873,642,586, we give it out, 

 three hundred and ninety-five quadrillions, eight hundred and 

 twenty trillions, one hundred and fifty-two billions, eight hun- 

 dred and seventy-three millions, six hundred and forty-two thou- 

 sand, five hundred and eighty-six. We are careful to dwell on 

 the articulation of the numbers. M. Inaudi repeats, as fast as he 

 comprehends it, each period of three figures ; then, when he has 

 taken in the complete number, he says confidently, " I know it," 

 and repeats the whole series with great volubility. 



I have witnessed his repetition in this way, without mistake, 

 of a series of twenty-four figures. M. Charcot, in order to com- 

 pare his capacity with that of Mondeux, another famous calcula- 

 tor, repeated with him the experiment, which had been tried with 

 Mondeux, of telling off a number of twenty-four figures, divided 

 into four periods, so that he might announce at will the six 

 figures included in each of the periods. Mondeux took six 

 minutes to reach the result ; M. Inaudi only had to hear the 

 figures given out. Thus a single hearing suffices M. Inaudi to 

 fix in his mind a long series of figures or the statement of a 

 complicated problem ; he does not go back to repeat the numbers 

 several times as we are obliged to do. He only asks, when the 

 series of figures is a little long, to have it pronounced slowly. 

 Once fixed in his memory, the number is retained with a precision 

 and sureness which it is hard to conceive. M. Inaudi can not 

 only repeat a number of twenty-four figures in the order in which 

 he heard it, but in an inverse order, beginning with the units ; he 

 can repeat half the number in one direction, and the other half 

 in the other direction ; and all this without hesitation, without 

 fatigue, and without mistakes. 



Ordinary persons can recollect a number of many figures 

 only a few seconds unless they have aids to their memory. M. 

 Inaudi's memory retains for a very long time the numbers that 

 have been given to him. He is in the habit of repeating at the 



